Advice on off grid solar when I am now fully on grid...

I've been through a futile attempt with my electric utility to go grid tied (last spring).  Without going into endless details I will just say that they are required to allow grid tied solar but my first hand experience was that they certainly aren't required to make it easy.  For example, requiring me to upgrade from a single TOU meter socket to a dual meter arrangement (Revenue meter socket and a solar production meter socket).  After months of inquiring with local electrical contractors the only one that would attempt the change over wanted $2k. Then Enphase engineers were not able to guarantee that their micro converter system would be happy working connected to a meter socket rather than a load center breaker (utility requirement).

So I am back to square one hoping to find a work around that will work for me.  I've done a solar survey and I've used PVWatts calculator to determine my array needs for 100% production.  I am aware a storage system is critical.  My question is about using "smart" controls that will allow me to connect the Enphase micro converters (@combiner box) to my load center.  I need to take this in baby steps so I understand how the grid feed and solar feed work together.  My town does not employ an electrical inspector, yeah really!  That doesn't mean I want to McGiver this together.  I want it safe so if the grid goes down it won't back feed.  I want to rely on solar for ,most/all of my electrical needs, but at the same time still be connected to the grid just in case.  Stupid idea?

Am I making this more complicated than it should be?  We are conservation minded folks and ideally I would just pull my meter and connect directly to solar and say goodbye to the power company and its electric and service fees.  I could go months on whatever we could get from poor solar production (which will be reality late Dec thru Feb).

Any advice would be appreciated but remember... baby steps and please no accronyms or highly technical talk unless you can tolerate a lot of back and forth clarifying 🤔

Tim

~4700 kW/year to meet current use
3 kW array (ground mount, single axis seasonal tracking)
Storage needs unknown

Tim Comer wrote:I've been through a futile attempt with my electric utility to go grid tied (last spring).  Without going into endless details I will just say that they are required to allow grid tied solar but my first hand experience was that they certainly aren't required to make it easy.  For example, requiring me to upgrade from a single TOU meter socket to a dual meter arrangement (Revenue meter socket and a solar production meter socket).  After months of inquiring with local electrical contractors the only one that would attempt the change over wanted $2k. Then Enphase engineers were not able to guarantee that their micro converter system would be happy working connected to a meter socket rather than a load center breaker (utility requirement).

So I am back to square one hoping to find a work around that will work for me.  I've done a solar survey and I've used PVWatts calculator to determine my array needs for 100% production.  I am aware a storage system is critical.  My question is about using "smart" controls that will allow me to connect the Enphase micro converters (@combiner box) to my load center.  I need to take this in baby steps so I understand how the grid feed and solar feed work together.  My town does not employ an electrical inspector, yeah really!  That doesn't mean I want to McGiver this together.  I want it safe so if the grid goes down it won't back feed.  I want to rely on solar for ,most/all of my electrical needs, but at the same time still be connected to the grid just in case.  Stupid idea?

Am I making this more complicated than it should be?  We are conservation minded folks and ideally I would just pull my meter and connect directly to solar and say goodbye to the power company and its electric and service fees.  I could go months on whatever we could get from poor solar production (which will be reality late Dec thru Feb).

Any advice would be appreciated but remember... baby steps and please no accronyms or highly technical talk unless you can tolerate a lot of back and forth clarifying 🤔

Tim

~4700 kW/year to meet current use
3 kW array (ground mount, single axis seasonal tracking)
Storage needs unknown

First off all modern grid tied inverters cannot back feed the system if it is down it needs the grid to lock onto... that said utilities still insist on a manual disconnect. So for your problem you have options...
In ontario we would call that two meter setup a micro fit system where they charge you one price and pay you another. I've seen several enphase systems running that way. Usually there is a seperate ac breaker panel on the pay meter side that acts as the utility required disconnect and the reference ac signal the micro inverters need. There are breakers for the micro inverter strings and they never touch your main utility panel...  Its expensive though. That should give enphase all the guidance they require.
If you cant get a setup like that to fly maybe a grid zero setup is what you should look into. In that scenario you have a battery based system running all the house and if you fall too low the grid connection just tops you off. For that you would need a new main breaker panel, transfer over all the loads your inverter can handle and use the grid as your inverters generator and program it to turn on if battery voltage falls below a certain threshold. Outback and schneider inverters both offer that. It was designed specifically for locations where the utilities were resistant to net metering... you cant get payback though as it does not send power back to the grid. It's a good way to be mostly solar yet have the grid there just in case...
Cheers,  David

So currently you have an active system hooked up to the grid?
Or is this a proposed system?
What place and electric company are you dealing with? Most electrical codes for most US states are based on the National Building Codes.  I took one of their inspection classes before I installed my system. My future inspector sat right next to me in class.

I have a grid-tied system that currently supplies 100% plus some. We do not get paid for excess with this company. I just have it in the "bank" in the event I need it.
I was required to add a manual cut-off in addition to the solaredge cut-off on the inverter which automatically shuts down if the grid goes down.
I chose grid-tied as I don't feel batteries are yet sustainable. They cost too much compared to lifetime vs grid which is already there. Also, we rarely lose power for an extended time so I don't even have a backup system.
In our state, the utility company has to provide the meter and we have a meter that measures both input and output, as it goes to and from the grid. Meaning the extra we don't use in the daytime is listed as "generated" and the "consumed" is what we use at night.   The difference, positive or negative is how much we pay for. The part we use directly from our panels I can only calculate because I have a monitoring system on each panel.  The small monthly fee is totally worth not buying enough batteries to power our house fully.  One downside is that if I do have to buy electricity, it is the highest cost per kwh because it is a small amount.
While I have not lately priced house batteries, I have priced prius batteries which start at $1500. I expect the one time cost of a meter is going to be far less than buying and rebuying batteries over the years.
Still, it seems unlikely to me that you would have anything to do with meter installation. I could see them installing a second meter and charging you, but not having you do it yourself.   But perhaps I am misunderstanding the situation?
I am considering adding a carport system to power an electric car if I ever get one. At this stage, it would still be advantageous for me to be grid-tied so the system could collect power whether I was using the car in the daytime or not vs paying for 2 sets of batteries to collect and store electricity, one in the car and one in the garage.

Thanks Carrie and David.  Just to answer your questions... I am grid power only now.  This is a proposed system.  Even though I haven't calculated the costs of battery storage I understand that it will almost double the system cost.  And the utility does not install the meter upgrade.  The customer does that at their own expense.  I actually had a copy of their approved meter sockets and was told by the local utility rep that he would not approve the $250 meter that is approved for my purposes and I would be required to go with another meter that was $1200 plus installation costs..  So you can maybe understand the hoops I would have to jump through to get a grid tied system.

So I'm getting the idea from your suggestions and others I've talked with that a grid tied solar system is the smartest way to go if i want to maximize solar generation.  Weighing that I was considering one of four options.

#1 is remain 100% grid supply with a small generator for emergency backup.  That is my current situation, no solar, 100% grid.  My experience with loss of grid power is infrequent, short durations (less than a minute) once or twice a year.  In 30+ years I remember just one outage of about an hour and another outage last fall which lasted about four hours.

#2 option is to build an off grid solar system and eliminate my utility's meter.  Pretty drastic and relies more heavily on a larger emergency generator to power more than my furnace and refrigeration needs; perhaps a 5kw unit.  With a 3kWh solar array I would probably shoot for a 48 hour battery backup while leaning on a generator upgrade to get through longer periods of low production.  This is kind of a trade off from the option of a large battery bank expense.  I am capable of living with minimal power for an extended period if needed.  To sum it up, I am much more flexible than the typical consumer.

#3 is building a grid tied solar system.  This seems to be what both of you are suggesting is the way to go.  Unfortunately I am not excited about working through the regulatory process.  Done that, been there with zero results so far.  Grid tied without battery back up seems to defeat the purpose I am going for.  I want independence from the utility.  Either complete independence or independence during grid outages.

#4 is to build a small off grid solar system to power a few appliances and charge a small storage bank.  I believe I could reasonably build a parallel electrical system in which I could switch back and forth from grid to solar manually without too much maintenance.   For instance, my refrigerator and freezer could be provided 120v wiring from an invertor and 120v from the grid depending on solar production.  Two parallel circuits independent of each other.

#4 is the one I will likely try.  It is a simple diy project that won't require expensive, smart switching components.  Switching will be totally manual and hopefully only have to be switched during my worst months, December through February.

Thanks again.  Tim

Sounds like a good plan. If you go for it I would suggest installing a good generator backup panel that disconnects both hots and the neutral from the grid. Something like this: https://www.homedepot.com/p/GE-60-Amp-8-Space-120-240V-Single-Phase-3-Wire-Flush-Mount-NEMA-1-Generator-Panel-TM860FCUGEN/203393780
Code compliant, flexible, and will make your life much simpler for moving over circuits.
Cheers,  good luck,
David

David Baillie wrote:Sounds like a good plan. If you go for it I would suggest installing a good generator backup panel that disconnects both hots and the neutral from the grid. Something like this: https://www.homedepot.com/p/GE-60-Amp-8-Space-120-240V-Single-Phase-3-Wire-Flush-Mount-NEMA-1-Generator-Panel-TM860FCUGEN/203393780
Code compliant, flexible, and will make your life much simpler for moving over circuits.
Cheers,  good luck,
David

Thanks David.  I edited my last post as I realize it is lacking in clarification.  The edit is waiting for Admin approval for some reason?

Anyway, to clarify, option #4, which is the likely direction I will go and is not tied at all to the grid.  Let me explain in more detail.  Then I'll wait for feedback on whether anyone does this and what their experience with it is.

I currently have two options for my forced air furnace that I am thinking of adopting for my refrigerator and freezer and maybe more appliances in the future after installing a solar system.  Years ago I changed the 120v wiring for my furnace to an extension cord type plug (15a) and a receptacle (15a).  So it is normally plugged into grid power.  It is no longer hard wired.  Within the reach of that extension cord furnace plug I've mounted a second receptacle wired to an "inlet" receptacle mounted on the outside of my house.  Again, not tied at all with the grid.  During an outage when I need my furnace I can run a 12g extension cord and a small inverter generator connected to the outdoor inlet and the furnace is plugged into the "generator outlet".  It has been used only once.  By the time I started the generator and fired up the furnace the grid came back on.  Not complaining! : )

I am going to build this system myself.  No contractor.  So my thought is to use a second electrical system.  A solar powered, off grid system with a small battery backup to get through an emergency of 48 hours or less.  From an inverter I would wire an alternate receptacle next to each appliance I want to run on solar.  At first, with a small solar system it would be used primarily for emergencies.  In the future, with a bigger solar array and possibly more battery capacity I could leave major appliances on the solar side.  I will still have a backup fossil fuel inverter generator which I hope would be used only as a last resort.

I know for the average homeowner this is a high maintenance system in terms of moving electrical cords from solar receptacle to grid receptacle.  I am not average and we are only talking rarely in an emergency and occasionally during low production periods.  For my purposes that low production period is mostly Dec through Feb.

Thanks again.  Tim

I am not sure I understand your goals.  Is it to save money on electricity? Be partially self sustaining? Learn more about actually having solar?

It doesn't sound like you have enough issues with power outages long enough to merit doing anything more than what you already have. Why go to the expense of having even a small battery back up system if the power never goes out?  It sounds expensive and complicated compared to just figuring out the regulations and complying. One  downside to partial solar I have found is when I did have to pay for overage it cost much more per KWh because I was no longer getting the "bulk" price and the first bit had lots of the extra costs built in.

I would investigate thorougly what exactly is required and how much it will cost. Get the requirement in print, in the event they are asking more than you legally must do and so they can't switch and add something at the last minute.  Then compare the cost to your off grid choices.  It would be a shame to spend more to be partially off grid instead of enjoying the benefit of fully solar.

One thing I have added that is particularly nice, is solar motion security lights in all the smaller windowless rooms in the house- bathrooms, laundry, etc. These run off of rechargable AA batteries, easily and cheaply found in most stores. I have maybe changed one set in the many years I have had them.  To reduce roof penetration, the wire is run through the roof ridge and the tiny panels are put on top. These are so nice I may add more.  The few hours the power does go out, at least the bathrooms still seem the same plus they turn themselves off.  I have considered building a self sufficent solar tool shed to charge the things that already use batteries, but not a priority since we currently make more than we use anyway.

I feel your pain. Like you said, utilities are required to comply but not required to make it easy! Our largest energy expenditure is heating so I'm looking at a partial solution like your #4... but with a rocket mass heater to cover the bulk of the heating needs. Central heating/AC still on grid since the wattage for those would would make a solar and battery storage system components very costly.

Also thinking of taking the branches that have minimal power needs off the breaker box and running them into a battery bank powered primarily by solar.  Then set it up so the grid powers this system when the batteries are not charged in the cloudy months. This would be an automatic one-way power situation so the grid takes over powering (or battery charging)  but power can never back-feed into the grid. Granted, I have limited understanding of this! I just know that there are one-way power diode technologies out there, though maybe just for DC power. More study needed since this may require too many power conversions to be practical.    

Carrie Graham wrote: I am not sure I understand your goals.  Is it to save money on electricity? Be partially self sustaining? Learn more about actually having solar?

It doesn't sound like you have enough issues with power outages long enough to merit doing anything more than what you already have. Why go to the expense of having even a small battery back up system if the power never goes out?  It sounds expensive and complicated compared to just figuring out the regulations and complying. One  downside to partial solar I have found is when I did have to pay for overage it cost much more per KWh because I was no longer getting the "bulk" price and the first bit had lots of the extra costs built in.

I would investigate thorougly what exactly is required and how much it will cost. Get the requirement in print, in the event they are asking more than you legally must do and so they can't switch and add something at the last minute.  Then compare the cost to your off grid choices.  It would be a shame to spend more to be partially off grid instead of enjoying the benefit of fully solar.

One thing I have added that is particularly nice, is solar motion security lights in all the smaller windowless rooms in the house- bathrooms, laundry, etc. These run off of rechargable AA batteries, easily and cheaply found in most stores. I have maybe changed one set in the many years I have had them.  To reduce roof penetration, the wire is run through the roof ridge and the tiny panels are put on top. These are so nice I may add more.  The few hours the power does go out, at least the bathrooms still seem the same plus they turn themselves off.  I have considered building a self sufficent solar tool shed to charge the things that already use batteries, but not a priority since we currently make more than we use anyway.

Thanks Carrie.  I get it, my posts where less than clear.  I'll try to clarify as I tried in this morning's reply to David without debating the issue of going partial or not. Well, at least I hope I will not sound argumentative.  First, the option I'm leaning toward as far as a solar system is not tied to the grid.  It is a second system.  No utility credits, offsets, etc.  See my previous post today.

"It doesn't sound like you have enough issues with power outages long enough to merit doing anything more than what you already have."
I haven't really done anything yet.  I have no solar system.  I'm just weighing my options and hoping to prepare for what may never happen; a grid outage of more than a few minutes.  Like insurance.  We all pay for insurance for things that we hope never happen.  In the future my solar system can be expanded to include more appliances, just not all.  In an emergency I do not need all.

And I'd be happy to comply with the utility regs if they would comply with what is in their own documentation for meter sockets that are approved for my application.  The the local utility rep just chooses to disregard that and tell me I have to install the more expensive meter socket with no explanation (yes I asked for one).  Going back to my original post, my utility is required to allow me to tie to the grid.  They are not required to make it easy or economical (economical is not synonymous with cheap).  In my state the legislature is not friendly to solar.  Actually they are close to dead set against it.  And we are not even a big hydrocarbon producing state.  I can't get any ground pushing the utility and certainly can't get ground contacting my representative.  I'm not in this for the fight, I'm in it to have a backup and not contribute to more hydrocarbon use.

"I would investigate thorougly what exactly is required..."
Been there, done that.  See above.

The solar lights sound appealing.  It is something I will consider for a couple areas in my home.

So thanks for your feedback.  Sorry, but I am beyond the Grid Tie thing

Tim

Could you just get the power company to drop in a meter pole, install a 30 amp(depending on your load needs) breaker, run a power cord from there to your system and not worry about a grid tie? I have an AC input on my off grid system that I use to plug into my generator but any AC power source would work.

I also have a 20 KW battery bank that cost just $3000. I would do a electric load calculation to determine how big a bank you would need.

Aaron Yarbrough wrote:Could you just get the power company to drop in a meter pole, install a 30 amp(depending on your load needs) breaker, run a power cord from there to your system and not worry about a grid tie? I have an AC input on my off grid system that I use to plug into my generator but any AC power source would work.

I also have a 20 KW battery bank that cost just $3000. I would do a electric load calculation to determine how big a bank you would need.

Nice setup Aaron. I would maybe consider upgrading that generator plug to a 30 amp rated cord to match the breakers at some point...
Cheers,  David

Aaron Yarbrough wrote:Could you just get the power company to drop in a meter pole, install a 30 amp(depending on your load needs) breaker, run a power cord from there to your system and not worry about a grid tie? I have an AC input on my off grid system that I use to plug into my generator but any AC power source would work.

I also have a 20 KW battery bank that cost just $3000. I would do a electric load calculation to determine how big a bank you would need.

Thanks.  I see what you are suggesting.  I sort of already have a small set up as you describe.  It just powers my furnace when the grid is down (or any other appliance I want to plug into that receptacle).

I've done the load calc based on a year and monthly needs (4700kWh/yr).  Is that what you are referring to?  Or narrowing it down to daily needs?  I also know individual average daily watts per day for my furnace , fridge and freezer.  Beyond that I haven't looked at it closely.

Tim

Good catch David. I should have put a disclaimer. I have my charge controller setup to only pull 15 amps from the A/C source because that's all I really need and all my generator can produce.

Tim, I would do a daily power load requirement. You might also do estimates of load requirements for different parts of the year if your electricity requirements vary much. That will give you a general idea of how big a battery bank you need. In our case I calculated a 10 KW daily requirement. With a 20 KW battery bank (flooded lead acid) I can theoretically run the house with no input from the solar panels for a day. In practice, even on overcast days we get some power from the panels and on those days we're not running our air conditioner as much so we can go 3 days or so with 90+% cloud cover and not need to run the generator.

A detailed analysis would help but there are ways to cheat battery size. Heat banking is a good one. During a winter day when you are producing good solar you put the thermostat up higher to run the furnace more then coast more during the evening. You are replacing battery size with stored heat.

David Baillie wrote:A detailed analysis would help but there are ways to cheat battery size. Heat banking is a good one. During a winter day when you are producing good solar you put the thermostat up higher to run the furnace more then coast more during the evening. You are replacing battery size with stored heat.

Good point David.  I'm sort of doing that now since we are on time of use rates.  We do laundry, bake, anything we can from 7p to 7a.  That includes bumping up the furnace before peak rates kick in at 7am.  So it's easy to adapt when we go solar.  Actually, part of the reason to increase solar production in the future is to be able to work in my workshop during the day with "free" energy.  Not that i don't run my woodworking machinery during the day now.  It'd just be better with solar capacity to run it.

Tim

Tim,

Very interesting thread!  I, too was interested in going grid-tied solar an age ago.  When we built our house we deliberately designed it with good Southern exposure to maximize natural sunlight in the winter and as a nice side effect, a roof line that would be conducive to adding in solar panels.  I did get a quote on adding solar to my house.  It was sobering.  Actually it was two quotes.  One would replace 10% of my normal electrical bill, the second 50%.  Both of them were staggeringly expensive.  I was left a bit jaded by the experience.

I have not done anything solar related with my house since that quote.  It is good to know that you are still interested and trying.  We just did not have the money for what either of the proposals, or more accurately, it would take decades at best to recoup our investment.  I do agree that storage can be a tricky issue, whether that is batteries which can get expensive and don't last forever or using the grid as a "battery" what with all the installation of backflow prevention devices.

I know that it may feel like you are stuck, but I wish you the best of luck, may it be better than ours was.

Eric

When I checked with our electric company, they wanted to install everything ... at a price.  When I crunched the numbers, it wasn’t going to work in my lifetime.  They also raised a fuss about any possibility of me back feeding their system.   I decided to wire my home with a redundant system for electricity I produce.  I have blue outlets for my system.   Of course, my electric bill drops a little each month.  

John F Dean wrote:When I checked with our electric company, they wanted to install everything ... at a price.  When I crunched the numbers, it wasn’t going to work in my lifetime.  They also raised a fuss about any possibility of me back feeding their system.   I decided to wire my home with a redundant system for electricity I produce.  I have blue outlets for my system.   Of course, my electric bill drops a little each month.  

Eric and Jiohn...  it has been frustrating.   A redundant system describes what I am leaning toward.  Seems pretty straight forward for a DIYer.  Funny, I was contemplating yellow receptacles to designate solar.

It's kind of odd to think of it this way but the cost is a deterrant and at the same time it isn't.  I'm not solely working from a payback period though it is important.  After Texas recently showed everyone its underbelly it is probably not the best time to be buying equipment as prices are bound to increase.  A few percent is understandable as demand goes up for array and storage costs.  But as we saw the middle men in the Texas market are ruthless.  I wonder how many of them will actually receive the huge electrical bills they sent out.

I haven't given up.  I found a supplier in central Michigan that I may be able to pick up panels from.  I'm not looking for many so the shipping would be prohibitive per watt.   It just happens to be on my way to my sister's place and once I've got the covid shot I could swing by and pick them up.  

Thanks for the interest.

Tim

Hi Tim, I'm living off-grid, the grid isn't available here and while I like it, it is very expensive. Redundant system sounds like a good way to go. It's what I'm planning to add to my system. We have a large solar array and battery bank but sometimes everything fails and I would like a separate system for key elements, like our internet and refrigeration. Another bit that I have found useful is keeping energy sources singular, so my propane stove doesn't require electricity.  I want my gas appliances to be just gas, my electrical to be just electrical, and having old school fall backs, like wood stoves, cold rooms (root cellar) etc.

We don't lose power for extended periods of time, but when there is a problem we lose power when the sun doesn't shine. Last year our battery bank failed, we had power during the day, but it shut down fairly quickly after that. For months we were waiting for new batteries.

This has been a cool thread to read.  I've debated putting in solar and cutting the line to the power plant but it's a big step.  I hadn't though of option 7 (which might be the same as David's option?)

Option 7:  Put in a big enough solar array and batteries to hopefully cover your needs.  Instead of having a big generator as your back up, leave the grid connected but only have it run a little line to the battery bank.  If the batteries are getting low and you'd normally crank up the generator, instead connect the utility juice to charge up the batteries.  You're still paying all the utility fees and bullshit but it might be cheaper than the big generator.  If the power goes out you're just limited to the capacity of your solar which should be enough to get by on.  After a few years and you get comfortable with it, cut the cord at that point...

Mike Haasl wrote:This has been a cool thread to read.  I've debated putting in solar and cutting the line to the power plant but it's a big step.  I hadn't though of option 7 (which might be the same as David's option?)

Option 7:  Put in a big enough solar array and batteries to hopefully cover your needs.  Instead of having a big generator as your back up, leave the grid connected but only have it run a little line to the battery bank.  If the batteries are getting low and you'd normally crank up the generator, instead connect the utility juice to charge up the batteries.  You're still paying all the utility fees and bullshit but it might be cheaper than the big generator.  If the power goes out you're just limited to the capacity of your solar which should be enough to get by on.  After a few years and you get comfortable with it, cut the cord at that point...

It is much cheaper to pay the monthly basic utility charge then to purchase, fuel and maintain say a 8kw propane generator which would be of comparable power to a battery charging grid line at 30 amps. Also there are some municipalities that own their utilities that will not let you not have a grid connection. Then there are mortgage and insurance issues as well. It is an easier way to grow yourself into solar I find. My previous home had it set up that way for 7 years and the new one will be similar only with a grid tie as well...

Hey?  What happened to option five and six?  And it has been a long time since I was involved in anything cool!

Just kidding.  

I'll start researching panels.  Not sure the Michigan source is a good choice.  Have to look into it.  Anything I find on craigslist I have to question.   Kind of hit and miss.  (330w AXIpremium HC 120cell BLK330, $165 ea)

But first, as David and Aaron have suggested I'll figure out my needs to power a few appliances "full time".  Then build a system around that with battery bank and an appropriate inverter.  Small scale.  I already have a 30a MPPT charge controller that I bought for my teardrop camper.  Very much overkill there but I knew that it would be useful if I go solar at home.  I'll go with a cheaper PWM CC for the camper.

The 30a MPPT will limit my array size a little but that's OK.  I'll add to or upgrade down the road as needed.  Not sure how to calculate how much panel I can throw at the 30a MPPT, but, I think it is a simple calc.  Just add up to amps of each panel and give it some fudge factor < 30a.

And being on "time of use" rates I can probably just charge my battery bank at night for day use if needed.

One thing I have in the back of my mind is when I buy the farm my kids won't be stuck trying to sell a mess of a home with crazy solar guy equipment that scares away buyers.  And then if my wife doesn't go to the farm at the same time the solar system can't be complicated to maintain.  She's not real interested in this idea.  She'll be looking for me on the farm to kick may a$$...

I couldn't remember where I wrote down the data for my furnace, refrigerator and freezer power use.  So I went looking for my killowatt meter.  Ha, found it still plugged in between my furnace and its outlet.  For 2596 hours!  That should be some valuable data to use for watts per day!

So 2596/24 is 108 days.  It's been recording since Nov. 17.  Great. Usage for 108 days was 184 kWh.  Do the math I come up with 1.703 kw per day.  So my solar needs to supply a reliable 1.703+ for my heating needs (Though I know it is not related to this calc I'll just say we rarely use our AC in summer.  Before last summer's 2 weeks of humid hi 80s we hadn't fired it up for at least two years.  Yeah, God's country!).

I vaguely remember the freezer and fridge using about 1.2 kWh per day each.  Does that sound reasonable?  I don't want to wait 108 days for highly reliable data on those!  Maybe a week would be enough.  Plugging it in now.

So let's say the furnace, fridge and freezer is what I'd like to start out with in my quest to power some appliances full time via solar/battery.  Added up we are talking 4.1 kWh (1497 per year, 423 oer month).

Being lazy I looked at my spreadsheet for electrical use from fall 2019.  Total average monthly use is 385 kWh (billed Nov '19 to Feb '20 - actual time is Oct thru Jan).  Or 12.83 kWh per day.  So, I would be happy with an initial reduction in my consumption of around 25%!

Now the fiddly bits.  What array size should I shoot for minimum?  What size battery bank (aHr) if I want 48 hours of backup power (LiFePo ish type battery)?  What size inverter (2500/3000p)?  Would my PVWatts calculator results help to determine this?  Feel free to check my math and my assumptions!

Tim

As for those gas generators, I was speaking to an electrician out here in Western Oklahoma - in the middle of the gas fields- after the most recent ice storm and he there was not enough gas pressure for many people to run their generators.

denise ra wrote:As for those gas generators, I was speaking to an electrician out here in Western Oklahoma - in the middle of the gas fields- after the most recent ice storm and he there was not enough gas pressure for many people to run their generators.

Another reason I hope to build a RMH in the future.  Natural gas will flow in an electrical outage here IF the supply is not interrupted.   On the scale of the Texas debacle I am assuming nothing.

Anyway, getting off topic.  Hoping for some feedback on my last posts.  Must be nice spring weather everywhere cause replies have slowed.  That's OK.  Enjoy the nice weather.  

Tim

Tim Comer wrote:I couldn't remember where I wrote down the data for my furnace, refrigerator and freezer power use.  So I went looking for my killowatt meter.  Ha, found it still plugged in between my furnace and its outlet.  For 2596 hours!  That should be some valuable data to use for watts per day!

So 2596/24 is 108 days.  It's been recording since Nov. 17.  Great. Usage for 108 days was 184 kWh.  Do the math I come up with 1.703 kw per day.  So my solar needs to supply a reliable 1.703+ for my heating needs (Though I know it is not related to this calc I'll just say we rarely use our AC in summer.  Before last summer's 2 weeks of humid hi 80s we hadn't fired it up for at least two years.  Yeah, God's country!).

I vaguely remember the freezer and fridge using about 1.2 kWh per day each.  Does that sound reasonable?  I don't want to wait 108 days for highly reliable data on those!  Maybe a week would be enough.  Plugging it in now.

So let's say the furnace, fridge and freezer is what I'd like to start out with in my quest to power some appliances full time via solar/battery.  Added up we are talking 4.1 kWh (1497 per year, 423 oer month).

Being lazy I looked at my spreadsheet for electrical use from fall 2019.  Total average monthly use is 385 kWh (billed Nov '19 to Feb '20 - actual time is Oct thru Jan).  Or 12.83 kWh per day.  So, I would be happy with an initial reduction in my consumption of around 25%!

Now the fiddly bits.  What array size should I shoot for minimum?  What size battery bank (aHr) if I want 48 hours of backup power (LiFePo ish type battery)?  What size inverter (2500/3000p)?  Would my PVWatts calculator results help to determine this?  Feel free to check my math and my assumptions!

Tim

first question is where are you; location and latitude. With that info you can figure out solar availability per day, month. Next would be solar availability at you actual site ie trees, hills obstructing view, angle of roof, etc.

Thanks David.  I'm not sure how to attach PVwatts results and my solar survey so I'll just describe what I'm seeing.

Using PVwatts... I've worked from a goal of 1500 kW per year in my location which results of an array of .9 kW.   So three 330 w panels is what I assume from that calculation to achieve 1500 kW per year.  I understand variables will likely reduce real world results.

In addition I have performed a solar survey at several locations on my property.  The ideal solar site is actually the ideal for aesthetics as well.  The ground mounted array will have single axis tilting capability (manual) to optimize production during the low production months.  As far as shading that area will only have substantial shading in December through February.   I don't expect to have much production in those months even without shading.  PVwatts is calculating 3.15 to 3.65 kWh / m2 /day for those three months.   That part of the year I think I would use the grid for powering appliances and maybe switch over the inverter to power low draw items such as lights and electronics.

If that answer is incomplete or unclear let me know.  I'll try to figure out how to add a screen shot of my PVwatts results.

Attachments for your viewing pleasure...

PVwatts results

My solar survey results are in the form of an downloadable attachment pdf...  Sorry for those phone users.  You probably won't be able to read it.

Tim Comer wrote:Attachments for your viewing pleasure...

PVwatts results

My solar survey results are in the form of an downloadable attachment pdf...  Sorry for those phone users.  You probably won't be able to read it.

Well having designed and installed systems I find their numbers for 45 degrees latitude highly optimistic for winter time. PV watts is geared for grid tied systems so no surprise there. I'm 45 degrees and I find an average for November December for off grid to be 1.5 hours with a fixed tilt of 45 degrees. Before battery charge efficiency and system losses. Install everything your charge controller can take and size for winter. The heavy costs now are batteries cabling disconnects and inverter panels are cheap at this point.
Which reminds me for your string voltage read the voc voltage of your panels add them together for string voltage and multiply by 1.25 and use that as your max voltage. Mppt chargers can take some extra currentp but will fry with over voltage. Check your manual. Cold climates in winter need some safety with string voltage as it goes really high on cold sunny days.
Cheers, David

I get what you are saying on the PVwatts calcs.  If you look at my estimates of hours of production in my solar survey I have accounted for very little production from Nov through Jan.   That isn't reflected in the raw data in results for PVwatts.

How does the PVwatts calculations being designed for grid tied systems effect the results I'm seeing.  I'm not sure if you are saying to find another calculator.  If you are in Ontario at 45 degrees I'm thinking lake effect weather patterns will reduce your production more than in my area.  Typical weather patterns for my area are not as "lake effect" influenced I would guess.  I might be assuming too much here though.  I'm guessing you are in southern ON?  Superior, Michigan, Huron and to a lesser effect Erie must determine a lot of your weather.

So I guess I'm close to an array design.  Three 330w panels, ground mounted single axis tilting from ~25 degrees to 85 degrees.  I'm debating wether to go with micro inverters.  They will in theory give me a little better performance and allow for cheaper wiring from the array into the house.  That will be offset by some efficiency loss converting to 12v battery charging.  I'm ok with that.  I have to find out how adding additional array strings effects charging to the battery bank.  Im not sure how that works.  Ive seen multiple small scale charge controllers charging one bank.  Not sure that is good at higher amps.

Tim

Tim Comer wrote:I get what you are saying on the PVwatts calcs.  If you look at my estimates of hours of production in my solar survey I have accounted for very little production from Nov through Jan.   That isn't reflected in the raw data in results for PVwatts.

How does the PVwatts calculations being designed for grid tied systems effect the results I'm seeing.  I'm not sure if you are saying to find another calculator.  If you are in Ontario at 45 degrees I'm thinking lake effect weather patterns will reduce your production more than in my area.  Typical weather patterns for my area are not as "lake effect" influenced I would guess.  I might be assuming too much here though.  I'm guessing you are in southern ON?  Superior, Michigan, Huron and to a lesser effect Erie must determine a lot of your weather.

So I guess I'm close to an array design.  Three 330w panels, ground mounted single axis tilting from ~25 degrees to 85 degrees.  I'm debating wether to go with micro inverters.  They will in theory give me a little better performance and allow for cheaper wiring from the array into the house.  That will be offset by some efficiency loss converting to 12v battery charging.  I'm ok with that.  I have to find out how adding additional array strings effects charging to the battery bank.  Im not sure how that works.  Ive seen multiple small scale charge controllers charging one bank.  Not sure that is good at higher amps.

Tim

Pv watts is as good as you can get for averaging but for grid tie systems there is no lost production so it all goes towards your tally. You get the same sun off grid just bunched up so you sometimes cant take advantage of it due to charged batteries, limits on charging speed etc. Nit much lake effect here but it's fairly cloudy in nov, dec . At this point you sound like you've answered most of the big questions. Please post as you go forwards.
Cheers,  David

David Baillie wrote:
Pv watts is as good as you can get for averaging but for grid tie systems there is no lost production so it all goes towards your tally. You get the same sun off grid just bunched up so you sometimes cant take advantage of it due to charged batteries, limits on charging speed etc. Nit much lake effect here but it's fairly cloudy in nov, dec . At this point you sound like you've answered most of the big questions. Please post as you go forwards.
Cheers,  David

OK, that makes sense.  I now understand what you mean.  I guess I don't care about excess production not being captured.  Eventually I'll build a battery bank big enough to take advantage of that "excess" (two or three days reserve in the bank).

Thanks for your advice...!

Tim

For what it is worth, my primary source is MWANDS out of Missouri.  Part of my reasoning is that I drive past their place several times a year ... so I save on shipping.

We're off-grid, so much of this thread doesn't apply in either direction, but some areas of overlap might be:

1. backups, and backups to the backups: throughout the solar elements in our system, we have found that gennys and batteries are the things that either need maintenance or die, so be prepared for these two areas.
 -  we have a propane storage tank, and a propane genny ... the key here is to have multiple gennys, in case one is down for maintenance or dies.  inexpensive but good $1k gennys are best, as this is sweet spot for us.
 - in batteries, we've switched to LiFePO4, which has really reduced battery maintenance to zero. but, even here, a battery bank might fail or need replacement under warranty, so have two. two in our case is a 300ah bank and a 100ah bank. if big bank is down, the little one is swapped in while awaiting "repairs".
 - i can report that solar panels (25-yr life), and to slightly lessor degree, inverters and such (5 years and still kicking), don't fail anywhere near the degree that batteries and gennys do.

2. I strongly second the idea of parallel power systems ... in the above posts, grid-tie and separate private solar and electrical wiring ... it isn't that hard these days. in our off-grid case, we have a separate small inverter/mppt coupled with the 100ah bank, and a pair of solar panels (acting as awning over a nearby window), and this drives our internet, tv's and related computing gear, parallel to the big system.
 - in a pinch, any component can be moved elsewhere to make up for repairs in the big system.
 - or, if catastrophe in the big system, this small system would drive internet stuff and freezer

3. stacked functions: we've moved small system components to our truck, and gone camping, with full power wherever we go. inverter, lightweight lifepo4 batteries move between these needs, and other solar panels are dedicated to the truck and camper shell.

Parallel systems, backups to the backups, stacking ... good!

Getting caught without backups (including w/o computing backups) ... bad!

I can also report a huge sigh of relief to being self-sufficient in power ... no monstrous power bills and regulations, no fee madness, etc. For those still grid-tied, parallel systems are key to reducing the madness, if you can pay someone to get there, or better, diy.

These folks are really the source these days, if diy:   diysolarforum.com