ᐅ Photovoltaic System and Air-to-Water Heat Pump – Profitability for a Single-Family Home Built to KfW 55 Energy Efficiency Standard
Created on: 11 Jan 2022 23:19
M
Maxwell8
Hello,
we are building a fairly large KFW55EE house with external dimensions of approximately 10x14m (33x46 feet) and a roof pitch of 15° (roof surfaces facing north and south).
We have a lot of window area (100m2 (1,076 sq ft)) and expect an energy consumption of about 7-9k kWh per year due to the size.
Heating is provided by underfloor heating with the Tecalor THZ 504 air-to-water heat pump.
Feed-in tariffs are no longer significant, but the electricity price is currently 45 cents/kWh.
We would have to finance the photovoltaic system ourselves because there is no sufficient budget left.
> From a profitability perspective, does a photovoltaic system make sense in our situation?
> What size and costs should we expect?
> Should it be installed directly or should we first prepare with conduits?
> We also have an attached 6x6m (20x20 feet) flat-roof garage on the east side. Would adding photovoltaic panels there be beneficial?
I will, of course, speak with companies but would like to gather some opinions beforehand.
Thank you in advance. 🙂
we are building a fairly large KFW55EE house with external dimensions of approximately 10x14m (33x46 feet) and a roof pitch of 15° (roof surfaces facing north and south).
We have a lot of window area (100m2 (1,076 sq ft)) and expect an energy consumption of about 7-9k kWh per year due to the size.
Heating is provided by underfloor heating with the Tecalor THZ 504 air-to-water heat pump.
Feed-in tariffs are no longer significant, but the electricity price is currently 45 cents/kWh.
We would have to finance the photovoltaic system ourselves because there is no sufficient budget left.
> From a profitability perspective, does a photovoltaic system make sense in our situation?
> What size and costs should we expect?
> Should it be installed directly or should we first prepare with conduits?
> We also have an attached 6x6m (20x20 feet) flat-roof garage on the east side. Would adding photovoltaic panels there be beneficial?
I will, of course, speak with companies but would like to gather some opinions beforehand.
Thank you in advance. 🙂
W
WilderSueden12 Jan 2022 19:25As mentioned earlier, the heat pump uses the most energy in winter. However, the days are short, the sun is low, and there are often several gray days in a row. In this case, the system is a supplementary source, but not more than that.
D
Deliverer13 Jan 2022 11:01In addition, 4.5 kWp is really not very large. On a gloomy day, you might only get 200 to 300 watts. You can easily increase the 14% yield to about 25% with a larger system. With some management (preventing overheating during the day), even more is possible. Much depends on the house itself, but the most important thing is to make the system as large as possible. When you have an electric car, you will definitely need every module.
This also means that for
And of course, no battery storage.
Everything else has already been answered.
This also means that for
Maxwell8 schrieb:you should definitely fill both sides completely. Adjust skylights in the plan to the module grid (otherwise, it often ruins space for 4 to 6 modules), avoid satellite dishes on the roof, and keep any ventilation pipes short so the solar installer doesn’t have to cut them later.
15° pitch (roof surfaces facing north and south).
And of course, no battery storage.
Everything else has already been answered.
W
WilderSueden13 Jan 2022 12:14Is the north side really worth it? 15 degrees is not particularly steep, but the panels are still almost constantly in the shade.
R
RotorMotor13 Jan 2022 12:39WilderSueden schrieb:
Is the north side really worth it? 15 degrees is not particularly steep, but the panels are almost constantly in the shade anyway. Usually, yes.
But it’s worth recalculating and also depends on other factors like buildings, chimneys, trees, and so on.
D
Deliverer13 Jan 2022 12:43Short answer: Definitely yes. Nowadays, north-facing roofs are built with a pitch of about 25° or less.
Longer answer: With a heat pump (and the associated high electricity consumption in winter), even steeper angles might work. There are websites I’m not allowed to name here that calculate the exact yield depending on location, orientation, and roof pitch. So you can estimate in advance how much extra cost north-facing panels can justify. And it’s not that much:
You don’t need an additional inverter, extra wiring, grounding, contactors, or planning— you’ve already paid for all that with the south-facing installation. For the north side, you only add a few modules, which—if your solar installer doesn’t overcharge you—cost only about two-thirds of what the south-facing modules did. Since the yield loss is less than a third, this investment pays off.
In bad weather, the module orientation barely matters; only the surface area counts. So if you want to charge your electric vehicle even on rainy days, or, more drastically, heat your home with a heat pump in winter, every kilowatt peak matters. You can’t imagine how little power you get during dull weather—it’s around 5-10%. That’s why, especially with electric vehicles, a 50 kWp system is actually still too small.
PS: I quickly checked for central Germany: south-facing roof at 15° pitch: 980 kWh/year, north-facing roof at 15° pitch: 750 kWh/year. You should consider installing from about 650 kWh/year upwards.
Longer answer: With a heat pump (and the associated high electricity consumption in winter), even steeper angles might work. There are websites I’m not allowed to name here that calculate the exact yield depending on location, orientation, and roof pitch. So you can estimate in advance how much extra cost north-facing panels can justify. And it’s not that much:
You don’t need an additional inverter, extra wiring, grounding, contactors, or planning— you’ve already paid for all that with the south-facing installation. For the north side, you only add a few modules, which—if your solar installer doesn’t overcharge you—cost only about two-thirds of what the south-facing modules did. Since the yield loss is less than a third, this investment pays off.
In bad weather, the module orientation barely matters; only the surface area counts. So if you want to charge your electric vehicle even on rainy days, or, more drastically, heat your home with a heat pump in winter, every kilowatt peak matters. You can’t imagine how little power you get during dull weather—it’s around 5-10%. That’s why, especially with electric vehicles, a 50 kWp system is actually still too small.
PS: I quickly checked for central Germany: south-facing roof at 15° pitch: 980 kWh/year, north-facing roof at 15° pitch: 750 kWh/year. You should consider installing from about 650 kWh/year upwards.
Deliverer schrieb:
Ps: I quickly checked for Central Germany: South-facing roof 15°: 980 kWh/year, North-facing roof 15°: 750 kWh/year
You should aim to build for at least 650 kWh/year. Per module, per square meter, or per “football field,” right? 🙂
Similar topics