ᐅ Photovoltaic System for 120 sqm of Living Space – Should the Entire Roof Be Covered?

So, we had our measurement appointment today.
We plan to fully cover both sides of the roof. Depending on shading calculations, this should yield around 12 to 15 kWh each.
We will include a battery storage system in the calculations.
The cost will greatly depend on what additional features are included.
A 10 kWh battery was estimated at 5,000€ (with a subsidy in NRW of 100€ per kWh), so about 4,000€ after the subsidy.
The solar panels (completely black) cost us around 230€ per panel.
Now it gets technical: The panels are connected in strings. Let’s say 8 panels are linked together in one string. Each panel can only deliver as much power as the weakest panel (for example, one produces less due to shading). This can significantly reduce the output of an entire string. To prevent this, there are “plug-ins” (power optimizers) that make each panel individually controllable. Of course, the appropriate inverter is also needed. Such a plug-in per panel costs about 60€. This adds up quickly. If you skip these extras and install, for example, a string inverter system, it will logically be cheaper.

Otherwise, the rule is: the larger the system, the cheaper it is proportionally and the faster it pays off (through feed-in tariffs and optimal use of storage/self-consumption).

@Kalibri Another argument in favor of south-facing PV systems is their excellent protection against summer overheating. Therefore, it is best to fully cover the roof while minimizing shading as much as possible. Storage systems usually only pay off if you receive subsidies (either direct grants or by qualifying for a better energy efficiency rating). Unlike the photovoltaic system itself, storage can also be easily retrofitted.

If possible, could you please post the total investment amount including labor time, etc., to get a better idea? Thank you.

Evolith schrieb:


We will fully cover both sides of the roof.

What do you mean exactly:
also panels on the north side (NE - NW)?

How much sunlight do you expect there?
Especially in the winter months, when the sun is lower in the sky, it will probably be quite dark there, right?

Or what kind of unusual roof shape is that?

konibar schrieb:

like now:
also panels on the north side (NE - NW)?

How much sunlight do you expect there?
Especially during the winter months, when the sun is lower, it will probably be quite dark there?!

Or what kind of unusual roof shape is that?

That’s not unusual. Below 25 degrees tilt angle, north—especially not exactly north—can be interesting.

Yield can be checked with PVGIS. The rest is simple math.

konibar schrieb:

Like now:
also panels on the north side (NE - NW)?

How much sunlight do you expect there?
Especially in the winter months, when the sun is lower, won’t it be rather dark there?

Or what kind of unusual roof shape is that?

Normal 35° roof pitch. I can only repeat what the technician told me. The current solar panels are monocrystalline modules. They have a significantly better efficiency than polycrystalline ones. They still generate a decent amount of energy even in overcast conditions. Therefore, north and east orientations make sense, as long as there is no shading in between.

Since we have a heat pump, which I want to supply as much as possible in the evening via solar power, we have to plan a correspondingly large system so that there is still a good yield in winter on both the north and south sides. In other words, a 5 kWh system won’t be sufficient.

Rumbi441 schrieb:

If possible, could you please post the total investment cost including labor time, etc., so we get an idea? Thanks

I will, as soon as I have a quote. Currently, I’m estimating 15,000–30,000 euros. They installed the system in one day.