ᐅ Roof Covering and Choosing a Solar Installer – Making the Decision?
Created on: 10 Aug 2022 18:21
E
Elias_dee
Hello everyone,
I am about to decide whether to hire a solar installer. I am building a turnkey single-family house with a general contractor in the 84xxx area, featuring a gable roof with a 25° pitch, oriented north/south. There are no skylights, chimney, or other obstructions on the roof, so conditions are optimal.
I am having some difficulty even requesting quotes and now have at least two offers. I would appreciate help evaluating and choosing between them (both the company and whether to include the north side). I have not asked for a battery system but might consider adding one later if it becomes more affordable.
So, first I am facing the question: include north side or not? I can fit about 25 modules on each side, resulting in roughly 10 kWp. PVGIS estimates around 10,000 kWh for south and about 7,000 kWh for north.
Offer 1 comes from a solar installer with many years of experience, who not only works on single-family houses but also builds large-scale systems in the megawatt range. My general contractor, who is building the house turnkey, also has long-standing experience with this installer and recommends them.
Offer 1 details:
- 20.5 kWp
- 50 x Q-Cells Q-Peak ML G10 410 heat pump compatible modules
- 50 x SolarEdge Power Optimizers, S440 Worldwide (v1)
- SolarEdge StorEdge three-phase inverters: SE10K-RWS-EU-APAC/AUS (v1) and SE7K-RWS-EU-APAC (v1)
- SolarEdge Smart Meter for self-consumption monitoring
- All other materials, installation, and commissioning services included
- Cost: €31,980 net, which equals approximately €1,560 net per kWp — reasonable for today, not really cheap but not very expensive either
Now to Offer 2. This offer is from a very small and new electrical company I found through a neighbor's recommendation. The company does not even have a finished website yet because it is so new, but they have already done electrical work in the development area (not sure about PV though). Two different neighbors have told me this company is good.
Offer 2 details:
- 20.9 kWp
- 51 x JinkoSolar Tiger NE HC N-Type black solar modules JKM410N-54HL4-B
- 2 x SMA inverters STP10.0-3SE-40
- 1 x SMA Sunny Home Manager HM-20
- Other materials are not specified here, but all installation, planning, and commissioning services are included
- Cost: €25,570 net, equaling approximately €1,223 net per kWp
My questions now:
- What do you generally think about the materials used?
- Are the SolarEdge power optimizers in Offer 1 really necessary? I expect practically no shading from trees, chimney, or anything else given the location
- Company 2 is probably a bit risky, but the price is really attractive. Is it worth taking the risk here?
- Does installing modules on the north side make sense at all in the case of Offer 1? If I calculate north and south separately, south obviously makes sense in both cases. North seems worthwhile (based on my calculation) only with Offer 2... with Offer 1 I would be running at a loss.
I would be very grateful for a brief assessment!
Best regards
I am about to decide whether to hire a solar installer. I am building a turnkey single-family house with a general contractor in the 84xxx area, featuring a gable roof with a 25° pitch, oriented north/south. There are no skylights, chimney, or other obstructions on the roof, so conditions are optimal.
I am having some difficulty even requesting quotes and now have at least two offers. I would appreciate help evaluating and choosing between them (both the company and whether to include the north side). I have not asked for a battery system but might consider adding one later if it becomes more affordable.
So, first I am facing the question: include north side or not? I can fit about 25 modules on each side, resulting in roughly 10 kWp. PVGIS estimates around 10,000 kWh for south and about 7,000 kWh for north.
Offer 1 comes from a solar installer with many years of experience, who not only works on single-family houses but also builds large-scale systems in the megawatt range. My general contractor, who is building the house turnkey, also has long-standing experience with this installer and recommends them.
Offer 1 details:
- 20.5 kWp
- 50 x Q-Cells Q-Peak ML G10 410 heat pump compatible modules
- 50 x SolarEdge Power Optimizers, S440 Worldwide (v1)
- SolarEdge StorEdge three-phase inverters: SE10K-RWS-EU-APAC/AUS (v1) and SE7K-RWS-EU-APAC (v1)
- SolarEdge Smart Meter for self-consumption monitoring
- All other materials, installation, and commissioning services included
- Cost: €31,980 net, which equals approximately €1,560 net per kWp — reasonable for today, not really cheap but not very expensive either
Now to Offer 2. This offer is from a very small and new electrical company I found through a neighbor's recommendation. The company does not even have a finished website yet because it is so new, but they have already done electrical work in the development area (not sure about PV though). Two different neighbors have told me this company is good.
Offer 2 details:
- 20.9 kWp
- 51 x JinkoSolar Tiger NE HC N-Type black solar modules JKM410N-54HL4-B
- 2 x SMA inverters STP10.0-3SE-40
- 1 x SMA Sunny Home Manager HM-20
- Other materials are not specified here, but all installation, planning, and commissioning services are included
- Cost: €25,570 net, equaling approximately €1,223 net per kWp
My questions now:
- What do you generally think about the materials used?
- Are the SolarEdge power optimizers in Offer 1 really necessary? I expect practically no shading from trees, chimney, or anything else given the location
- Company 2 is probably a bit risky, but the price is really attractive. Is it worth taking the risk here?
- Does installing modules on the north side make sense at all in the case of Offer 1? If I calculate north and south separately, south obviously makes sense in both cases. North seems worthwhile (based on my calculation) only with Offer 2... with Offer 1 I would be running at a loss.
I would be very grateful for a brief assessment!
Best regards
E
Elias_dee14 Aug 2022 14:43RotorMotor schrieb:
Still the same question. Why no 20kW inverter?That’s a good question. I will clarify with the solar technician!RotorMotor schrieb:
Still the same question. Why not a 20kW inverter?Because it is still unnecessary. Half the output faces north! A 20kW inverter would be completely oversized.
R
RotorMotor14 Aug 2022 16:23guckuck2 schrieb:
Because it’s still unnecessary. Half the output faces north! A 20 kW inverter would be totally oversized.Ah, so that’s why 2x10 kW instead of 1x20 kW. ;-)A 10 kW inverter is clearly too small.
A 15 kW inverter might be slightly too small but could work.
A 20 kW inverter might cost around 200€ more than a 15 kW one.
But well, this should/could be simulated again.
I always find 2 inverters disadvantageous in terms of space, cost, efficiency, failure risk, management, and so on.
RotorMotor schrieb:
Ah, so that’s why 2x10kW instead of 1x20kW. ;-)
A 10kW inverter is clearly too small.
A 15kW inverter might be slightly undersized, but could work.
A 20kW inverter costs maybe €200 more than a 15kW.
But well, that should be simulated again.
I always find 2 inverters disadvantageous due to space requirements, costs, efficiency, risk of failure, management, and so on. So, once again. Half of the system faces south, which accounts for 10kWp. When the sun is shining at its peak around noon, the maximum power from the south side will be about 10kW, limited to 70% by the roof.
If the north-facing roof produces any yield—which it will never reach 10kW—the south side’s production will correspondingly be significantly lower.
I am even beginning to agree that a 10kW inverter might be too small for the whole system (!!) but sizing above 15kW is definitely inappropriate. You might run into issues with too low string voltage.
Two inverters provide the advantage of redundancy (why do you claim the opposite? Strange) and you can register two separate systems, which can have benefits in feed-in tariffs and/or taxes. Also, one of the systems could be set up as a full feed-in system, etc.—you have to see if such a setup might be worthwhile.
I would recommend presenting the roof setup in a well-known forum.
R
RotorMotor14 Aug 2022 18:25guckuck2 schrieb:
If the north roof yields energy It’s exactly the same as south-facing at noon.
guckuck2 schrieb:
But more than 15 is definitely a miscalculation. You might have issues with too low string voltage. Unfortunately, you are wrong here as well.
Snowy36 schrieb:
left everything as usual during the holiday period and went away: 10 kWh consumption daily...Sorry, that's practically impossible. That would amount to about 3650 kWh per year, without cooking, dishwasher, ironing, hairdryer, TV, home office, etc. So it can't be true...
That much standby consumption... 🙄
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