Mike,
There's some possibility you will need to temper your expectations about solar generation.
As a background I setup and ran offgrid on my own house for 2 years, built my solar setup of 9 panels 300 watt, 3500watt outback inverter, 60 amp tristar mppt charge controller, built solar racks and my entire wiring setup.
First you need to figure out what sort of solar you're going to get, this can vary wildly, you need to figure winter vs summer coverage where you're planning your panels. Having full sun exposure is VERY different from having partial. A full straight on blast of sunlight on your panels can produce even higher than their rated wattage, 2800 watts for me, but even a branch of shade on a single string on that panel will drop you to 1200watts. Only direct 90 degree sunlight will give you maximum solar, even full sunlight early in the morning at an angle may only produce 900-1000 watts on those same panels.
While one person mentioned getting 600 watts on a rainy day, here in the pacific northwest on really dark and rainy days my array would generate about 180watt hours for the entire day.
The amount of sun and clear sun will literally change your solar production in a range of 1/20th your rated solar panels per day up to my personal maximum was 14kwh in a day (just over 5 solar hours). To get more solar hours is tough as it requires tracking panels that will follow the sun straight on. I live in the fraser valley of british columbia so that is about 1hr from vancouver, about 30 minutes north of the US border (in regards to latitude) and live on a south facing mountain.
My own solar was impeded by trees across the road and neighbor trees which would have made a modest difference, perhaps an additional solar hour per day maximum. In the winter I would get shade on the panels in the middle of the day in the depths of winter. Often a non-issue though in that the gloom and rain here would cause us to have months of an accumulated total of about 10 solar hours for the entire month (28kwh for an entire month total).
In addition to the potential issues with solars variance, which can be extreme ranging from 0.05-6x your rated panels depending on weather, you will also run into inverter drain. Inverters, mine being an outback 3.5kw, drain around 40-45watts per hour so they accounted for about 1kwh/day drain just from the inverter being active, to have available AC power requires a standby power drain that is in addition to your actual appliance consumption. All inverters will give you a similar issue and the drain is based on the maximum potential KW power of the inverter itself.
You will also want to really monitor your KWH consumption of power before you look to size your system. While you've tested your deep freeze, deep freezes aren't the biggest drain in the house in our experience. You've mentioned wanting to power a refrigerator. That was our biggest unavoidable consumption. We had purchased a brand new samsung 20cuft refrigerator about 6 months prior to going offgrid and the kwh consumption per day was 2.5kwh per day just for the fridge. I would highly suggest using the kilowatt on your fridge for a few days and calculating your power consumption.
Another big issue for us was furnace consumption. The forced air blower on our furnace (and the glowplug for startup) would consume 650 watts. When calculating our furnace use, our furnace would run for 3.5-4hrs per day in the winter time. That was another possible 2.8kwh per day of consumption.
I definitely advise, before spending money or sizing a system, run your kilowatt on your chosen appliances, if you can, get one on your furnace as well if thats whats intended.
What I ended up doing, once we went back onto grid power, was to get a manual multi-circuit transfer switch, this allowed me to toggle individual house circuits between grid and solar at will, each circuit is a 3 way toggle, grid-off-solar and you can actually switch them fast enough to flip electronics between power sources uninterrupted. This allowed me to toggle the entire house over to solar (as I had that few of circuits) at will when there were power outages, and I routinely ran about 1/2 the house on the system, when there was poor solar for awhile and the batteries got lower in charge, I would just switch those circuits back to grid power and shut down the inverter until the solar charged up the batteries again.
If you do get batteries (which I did). Lead acid are cheaper by far of various options but have a very poor charging profile that limits the potential of solar dramatically. Lead acid batteries will have very poor life the lower you discharge the batteries, so much so that by the time you get down to 50% charge most inverters will be automatically powering off to prevent battery damage. Lead acid take a long time to charge too as once they reach 85% charge their charge rate dramatically slows as impedance builds in the batteries. Float charging can generally take longer than you will ever get a sustained burst of solar activity so often your batteries will not get fully charged unless you have consecutive sustained days of good sun and low consumption. Also the round trip efficiency can end up requiring alot more power than you get back out of the batteries, ie: you use 5kwh of power, it often will require 6-6.5kwh or more to recharge that battery bank.
Lithium batteries (lifepo4 being a good choice) typically run about 4x the price per kwh but can FULLY charge in 2 hrs if you have the solar panels for it, compare that to lead acids 5-6hrs and you can start to see the benefits. Lifepo4 batteries will often be rated for 2000-10,000 cycles too as opposed to lead acids often being 500-800. These cycle lengths are how many times they can be reliably charged, lower discharges over their life can extend these lifetimes quite a bit as well (in both cases). You also get a stronger charge efficiency, 5kwh of consumption may only require 5.5kwh to replace and can be replaced faster with a larger array (up to 2hr charge time from an 80% discharge).
As for wiring the panels. Typically you will only wire 3 panels at a time in series. The majority of charge controllers are rated for a max voltage of around 120 volts. You CAN find higher but you need to make sure you check what you're doing. Those are rated maximums and you are typically trying to make sure you have a safety margin underneath that, many panels are around 10 amp 30 volt but can go higher based on weather and solar (voltage wise). Higher voltage transfers easier, as you add amps you cause impedance, getting higher voltage rather than amps lets you use lower gauge wire.
Use the wire calculators that were mentioned for figuring it out. 3 panels in series will still be 10 amps but 90 volts. One thing I did was get 8 gauge wire and ran separate lines for each of my panel strings, around 100ft, this caused minimal loss, if I had put my strings together in parallel at the panels I would have needed at least 2 gauge or 0 gauge wire to get the same efficiency as I would have been pushing 30 amps. The 8 gauge wire, even the 6x 100' lengths was VASTLY cheaper than 2x 100 2 gauge wire would have been. I brought the strings into parallel where my battery bank and charge controller were.
If you go lithium batteries they have different temperature tolerances than lead acid, do your research on temperatures first based on your battery tech and it might affect where you put your batteries and charge controller. The sooner you can get to AC power the easier it is to transfer that power with lower loss hence lower gauge wire. For temperatures lead acid prefers around 25 celcius which is around 77 Fahrenheit for optimal use. The lithiums are more tolerant of ranges but have serious issues below 30 Fahrenheit.
Overall solar is a good experience but you do need to temper your expectations of power. I often said, if it only rained for 5 out of 7 days here and we only had 2 full days of sun a week that we could do solar GREAT, but the reality was that we would sometimes get WEEKS of poor weather, or entire months without seeing the sun. Those weeks of interminable rain can result in your solar array producing much less than your inverter drains every day leading to constant net loss of power before you've even turned on a lightbulb.
The major benefit though is the availability of power, once you have that battery bank and charge controller and generator (the inverter actually is what charges the battery bank from a generator because you're bringing in AC power for that), then you have ALOT of freedom.
We managed to optimize our house to be able to sustainably survive on 2.8kwh/day with freezers, lights and refrigeration and heat. Our 20kwh lead acid battery bank (which only lets you use about 10kwh) would last us for around 4 days without any solar. 5 Hours of charge with our propane fueled generator would bring us back up to around 95% battery and enough to last another 4 days. If we managed this well it would run about $25-$30 in propane fuel to run entirely on generator and battery banks. This opposed to the $30/day it would cost to run entirely on generator. This is because your generator will consume about 40% of its maximum fuel use under load, just idling. So if you fire up a generator, make maximum use of it otherwise you're wasting fuel.
I have plenty of other tips as well, things like sizing your system based on your batteries and necessary consumption and other tips if you're interested.
One note as well. Go with a 48v setup. Most charge controllers are AMP based, ie: 40 amp, 60 amp etc. They're still an expensive piece of hardware for an mppt charge controller. If you decide to use a 12v setup your 60 amp charge controller will only output a max of 720 watts. It is limited to 60 amps, whether thats a 48v setup (2880 watts) or a 12v setup (720 watts).
I made that mistake early on and had to address it. The main issue isn't the charge controller in that scenario, its the inverter. Inverters are hard set to a specific input voltage range so a 12v inverter can't run off a 24v system or a 48v system. A 48v inverter won't run off a 12v system. Your good pure sine inverter is going to be the next most expensive piece of hardware after your battery bank so this is important early in the design decision.
The voltage has nothing to do with your solar array setup and just has to do with how you setup your battery array. Stick with 48v though, can use lighter gauge wire for your battery bank and various wiring there than if you use 12v, you're also using lower amps which is generally better for heat and losses etc.
If you're sizing your array, realize that there's a maximum charging speed for any battery array. If you are running lead acid, their maximum charge speed is around c/8 (for trojan t-105, each battery you look at should have charge specs in their spec sheets) which is 1/8th their capacity. Lead acid slow as they get close to full but this gets you in the proper ballpark. That means having a 5kw solar array when you have a 20kw battery bank is useless. Your battery bank can only charge at a maximum of 2600 watts, the 5kw solar array is way under used. (You also would need a much bigger charge controller to make use of it, but with a 20kw battery bank you couldn't charge that fast anyways).
The amount of battery storage will absolutely dictate how big a solar array you should look at. While there is some argument for over-paneling your setup in that you produce more in offtimes, there's issues with overloading your charge controller, not being able to use that power, having to deal with dump power or other issues to get rid of excess solar electricity and possibly blowing fuses and spending alot of money in infrastructure and racking and cabling for something you fundamentally have no way to properly utilize.
If you look at a lithium battery array you can definitely look at a larger solar setup for similar capacity. A 10kw lithium array can use between 8kw-10kw (documentation is sketchy so I'm uncertain if you can actually consume the 100% capacity they claim). Regardless you can charge at c/2 for most lifepo4 setups which would mean 5kw per hour. This means you would have potentially similar capacity as a 20kw lead acid but you could use a solar array 2x the size and charge the entire thing in 2hrs of sun (although you would need a bigger or multiple charge controllers).
Charge controllers can be paralleled into battery banks without issues as well. Expanding your system is pretty easy, the thing to avoid though is mixing old and new lead acid battery banks as they have to all be ran in parallel to each other (in 48v strings) and capacity differences in different battery ages will cause total capacity disparities and can lead to the banks slowly draining or unequally charging causing discharge drains. Adding more panels can be done in strings, you need to keep your inputting voltages similar. I have 4x 265watt panels and 5x 300 watt panels. Basically your voltages will align with your lowest string voltages which means if you add higher voltage panels later on, you'll end up just basically running them as though they're the lower voltage of the originals.
The inverters you go with often will allow twinning or stacking, check the literature on your brand, I know siemens inverters that someone mentioned can be paralleled or stacked into I think 3 or 4 together to increase capacity and phase your power to 240v which is good for welding and other high voltage draws.
Increasing your system size though pretty much all rotates around your batteries though, having a massive array is useless if you can't charge your batteries that fast anyways. Its a different scenario if you're grid tied of course, you basically trade the independence and reliability of your own power and the cost of the battery system, to the utility to essentially replace a battery system with the utility (and make some possible money at the same time). The exchange (here in BC anyways) is that our utility company has legal authority to come in and do as they please with your system and its an absolute requirement that your system go offline when the utility power is down (so you're not dangerously backfeeding into the lines when linemen may be working on the lines). This means that your power is out along with everyone elses when it goes down.
Lots to think about I hope there's been some helpful info in here.
A helpful utility for android cell phones:
https://play.google.com/store/apps/details?id=com.andymstone.sunposition
That is a solar tracker app that lets you set a calendar day and uses your phone and location and the camera to show you the trajectory of the sun on a specific calendar day. This can be used to figure out your solar coverage in specific areas to determine what sort of solar exposure you will get which can vary alot based on time of year.
