Seeking advice/expertise for a new solar system on tile roof in Catalunya/Spain

I'm suffering from impostor syndrome and have forgotten my high school math.

Location: near Cubelles in Catalunya, Spain
Slope: wish I knew, picture attached.
Roofing: Individual red tiles (So...brackets? hooks? How do I best mount panels?)
Best roof orientation: western half of roof (mountain is to south, east has a fireplace chimney)
Area of available roof: about 16 square meters (3m north/south side of rectangle, 5.3m east/west side)
Energy goal: 5KWH (? based on current usage in a different house, solar plan is for what has been a summer house but we'll be there fulltime soon)
Mechanical room: pantry located at the southeast corner below panels
Gear options: Local big box Obramat has...

Battery: PYLONTECH US5000 4.8KWH lithium battery 48V. (Larger are available but for the price jump a second battery later if needed seems sensible to me. Please correct me if I'm wrong. This is an on-grid house built in the 1980s.)

Inverter choices:
AXPERT KING II or HUAWEI (about 100 euro more for the latter). Both 5KWH, 48V  Opinions of brands?

Panels:
JA SOLAR either 505W or 565W. Sized 2.1m x 1.1m or 2.3 x 1.1m, 26kg or 28kg, about 10 euro more for the larger panels. (So 8 or 10 fit depending on how they're secured?)

My husband thinks his brother can help with hooking up the electrical end of things if someone else does the part up on the roof. I think he or the hardware store employees can point us in the right direction for cables, fusebox, etc.

Am I crazy to think we could semi-DIY this rather than go to a specialist designer/installer? Is the latest tech that much better than what' s easily available? When sold as kits or packages 5kwH is priced at least 10,000 euro for what looks to me like about 3,500 worth of gear. Of course the labor cost isn't nothing but it seems like there's a few thousand worth of padding for those afraid to put it together themselves. That's me, terrified but a cheapskate.

Open to advice and rudimentary education about electrical systems!

Thanks,
Eileen

Hi Eileen,
that is a bunch of questions you have. Not surprisingly there are a lot of varying answers with "it depends" attached.


I think there's two ways of getting at this, from the demand side and from the available, usable space side.

Let's start with the space side:
From what I understand you have the western roof available? Could you make a rough sketch of the roof with some dimensions? Like a blueprint, with the orientation showing.

Next would be to find out what pitch the roof is. Measure the lowest and the highest point, I'm happy to help you with the math afterwards.


Some questions on the demand side:

I understand you are grid connected? Can you find out what your monthly and yearly consume is? From that and some questions about habits (working from home, all out of the house during the day, etc) we could more or less find out when you need how much of energy. And from that we could try to gauge a battery size.

The size of inverter depends on the power (kWp) of the solar panels. The size of the batteries (kWh) depends on how long you want to only use batteries.

We live with 3 people off grid and have 7,5 kWh of battery (3x Pylontech US2500) combined with 6 panels (roughly 2,4 kWp). That gets us through 1,5 rainy days.
So 5 kWh battery on grid seems like a lot to me. But it depends on what you want to achieve.
Do you want to not use any grid power?
Do you want to save on utility cost?

I think the specifics of materials, who and how to install are better discussed after you know a bit more what you want and need.

Oops, read the post below where I attached both photos instead of duplicates

Thanks in advance!

Hi Benjamin,

I'm grateful for your insights! Here's the plan which shows the roof shape. As built it isn't exactly the same (fireplace not in this position on to the east, but the west is the same other than a pantry bumped out where the back porch was. Roofline there didn't change). West is the bottom of the page in the plan/roof photo.

Roof is labeled 30 percent pitch. Missed that the first time.

We are a family of four with two adults on computers for hours at home most days. Big fridge and freezer. 80 gallon aquarium. Multiple loads of laundry each week for twin boys. European style run for hours and call it efficiency. There's a second fridge and workshop of power tools in the garage on this site. Not built as a four-seasons house so hard to heat and cool. AC and space heaters. Only one of us is a Permie ;)

I don't have good info on usage since inlaws previously used it July and August only with occasional weekend caretaking the rest of the year. In our current four bedroom flat we used 150kWh in the last month and 225kWh was the highest month's usage in the last year. This flat has gas heat so next winter in the solar house it will be electric heat or the fireplace.

My goal is to capture what I can on the usable roof and build in some resilience against outages. I don't think we'll be independent or try to sell back to the grid. Spain sometimes has solar tax incentives but has also pulled the rug out from under some big solar investors in the past so my husband isn't factoring any government incentives in.

Thanks in advance!

Hi Eileen,
ok, that's some more information.

The photo of the house you sent is the view from the north? So the right handed roof would be where the panels go? On the other side I see a lot of trees... so I'm hoping it's the right handed side on the photo.

You say you have a 5,3 by 3 m surface. I can only fit 5 panels on that. How do you count 8?

5 panels would give you the nominal power of 2525 W or 2825 W.

On PVGIS I get a yearly production of 3000 kWh for 90° (West) and 30° slope. Highest monthly yield around 400 kWh and lowest around 100 kWh.


A little backup is nice, but the inverter/battery charger/brain of the installation needs to be set up for a start after a blackout. Something to keep in mind.

10k euro doesn't seem so off to me if its including a battery and all the work. But of course a company wants to earn something. So if you think you have the expertise and the time it's worth thinking about it.
DC currents are tricky though. Do you have a real electrician at hand?
Also I don't know about your house insurance and the legality of grid connected DIY PV-systems.

Hi Benjamin,

Looks like my last reply didn't post, maybe the attachments I made with your cool tools on your linked website were the problem. (?)

(The part of the plan labeled section AA is through the middle of the house showing where the interior doors to the bathroom and medium bedroom are. I don't know why it isn't the house front, which is the north side as shown in the photo from the street.)

It should be 6 of the larger panels I think, definitely not 8 as I said. (My husband and I started this plan considering a roof extension that would add 2m to the northeast corner of the house adding to the 5.3 dimension to cover an outdoor laundry area. It's probably too shady but I still had that extra area on the brain.) My measurements were on the ground so once we add in the pitch it adds almost a half meter of roof. 3.46m x 5.3m. You're right that my plan is for the right hand side in that photo where the trees rule out the east/left.

Six big panels gets me to 3510KwH and I think it's 3.29 KwP peak power with panel efficiency rating listed as 21.4.

My brother in law is a nuclear physicist, not an electrian. He did the electrical for the garage/workshop (all AC) at the site and it wasn't an issue with our insurer. He might consider DC too hot/dangerous and nobody wants to work on the roof so I'm enlisting my native speaker to get some estimates for professional work.

The power company estimate for a package including installation was around 7,000 euro which would clear the hurtle of permissions and open up a possibility for selling back. My husband didn't get specifics about hardware when he asked though, so I would want to know more before doing that. I watched a lot of YT videos today that showed a range of features on inverters that go beyond the basic. They're probably not all available in Spain, but it might be worth ordering from Germany or wherever to get something better than what Obramat has.

If you could tell me more about what redundancy or solution is needed to avoid post-blackout kind of problems you mentioned. I'm very interested. Is it just a matter of losing all of your programmed settings or of needing to install something that alerts or disconnects when the battery is low?

Thanks,
Eileen

Hey Eileen,
Autosolar has a lot of hardware available. And their technicians are pretty good.
When choosing the “brain” (inverter, battery charger) you just have to make sure it’s suited to supply power to the house in case of an power outage. It should be called something like backup function or similar.
Also if I were to choose the inverter for our house I would opt for one that is easily connected to a smart home type of thing.

Just wrapping up this post with a thread to show we did it. In the end we bought a package from the electric company. That was the only way to sell back to the grid and future-proof our investment for the time when we might not be living here full time. My in-laws own this house so some of the decisions were out of my hands, but for summer at least we're exceeding our own daily consumption and getting about 2 euro back daily. In truth it was a pretty frustrating experience. The installation happened five weeks past the salesman's estimate of 'three or four weeks' and those were during peak summer months when it could have been paying for itself while we traveled. My husband paid somewhere between 8-9,000 euro with a partial rebate (not yet refunded as I understand it, said to be about half, but I'll believe it when I see it.) He paid in full upfront without a guarantee of installation date. (Yep, that sounds stupid to me too but that's Spanish monopoly for ya.) We didn't get the specs on the panels that I wanted (the company makes an argument for stability in high heat over the latest, higher numbered panels) nor did I get to choose the inverter, but it's done. We had a bit of tree work done at our expense too to avoid it being wiped out by a stray pine. (Fingers crossed about the remaining ones in the stand above our house; They're a protected species and you need to have a good argument for their removal.) The couple of euro is presumably against our winter bills but there might also be a scheme where you have to spend it on other utilities infrastructure like a new boiler or something. Our family is working to shift our habits from using electricity in off-peak, lower cost hours to best solar panel hours. Thanks for your advice and encouragement. Husband and outdoor laundry station for scale ;)