ᐅ Switching from Gas to Solar / Photovoltaics with or without a Heat Pump

Deliverer schrieb:

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A storage system becomes worthwhile at around 60 cents per kWh electricity price. So it really depends on your crystal ball whether you want to do it. With a heat pump, I would only consider adding storage if you exceed 20 kWp. If your photovoltaic system is smaller, the heat pump will otherwise use up almost all the electricity, leaving nothing for the storage. An electric car worsens the storage balance even more, since from October to February it effectively consumes almost no kWh from the storage...

I can’t think of any funding through loans (KfW). But the BAFA offers 35-40% funding including everything for heat pump replacement against gas.

My own calculations result in a slightly more favorable figure around 40-45 cents per kWh, contrary to my previous opinion. But maybe not everything should be considered purely from a commercial perspective?

Furthermore, I have a ground-source heat pump, a BEV (with only a 35.5 kWh battery), and a rather small 6.5 kWp photovoltaic system. At the moment, I generate about 40 kWh daily. Only 15-17 kWh of that is used in the house (including heat pump and household electricity). In summer, it will probably be less. Currently, I just can’t get the rest “filled” into the BEV and get annoyed by every kWh fed back into the grid. By the way, I’m talking about a semi-detached house with two residential units and a total living area of about 130 m² (1400 sq ft).

Of course, it also depends on where the car is parked during the day (at home, at work?) and how well you optimize the heat pump (when it starts, “heating” the storage hot during sunshine). When dishwashers, washing machines, and dryers run, etc. I see a lot of potential for optimization; having a battery offers more flexibility. Ours costs about €600 per kWh (RCT). So everything is very dependent on individual circumstances...

By the way, I’m also hopeful that bidirectional charging will soon be politically supported and thus permitted. When finally, in about three years, the Munich startup with the Sion is ready ... perfect.

Thanks for your answers. I will try to address them.

Deliverer schrieb:

Solar thermal is never worthwhile.

Why not?

Is that why you always recommend photovoltaic panels plus a heat pump?

Nida35a schrieb:

I hope the underfloor heating is designed for 30 degrees, since it has already been renovated.

Yes, it is designed for 30°C (86°F).

Deliverer schrieb:

Semi-detached house, renovated in 2014 sounds like a fairly moderate heating energy demand. How much gas do you use per year?
With that number, you can roughly estimate the required heat pump capacity.

Our semi-detached house is 161 m² (1733 sq ft), 2 adults + 2 children. Two home offices in full use + server running 18/7.
Electricity consumption: 4600 kWh
Gas consumption: 28000 kWh

We do not currently have an electric car, but would like to have the option to charge one at home in the future.
Roof pitch: 33°, facing south.

i_b_n_a_n schrieb:

Ours costs about €600 per kWh (RCT).

Then the calculation with 45 cents is correct. However, most batteries are purchased for around €1000 per kWh.
With a small photovoltaic system, you probably won’t get enough cycles to break even. You should aim for about 200 full charge-discharge cycles within 15 years to recover the costs.

free2abc schrieb:

Why not?

Solar thermal and photovoltaic systems provide relatively little energy in winter. Short days, low sun angles, and often gloomy gray weather simply aren’t suitable conditions for solar energy.

It’s different in summer, but the problem with solar thermal systems is the surplus. In summer, you could heat an entire swimming pool, but only need a few liters for showering. The rest just sits uselessly in the pipes. With photovoltaic surpluses, at least you can feed them back into the grid and get some compensation for it.

free2abc schrieb:

Why not?

Because it either doesn’t run when you need it or runs full blast when you don’t. And considering it can only reduce heating costs by a really small amount (5-15%), it’s too expensive AND takes the prime spot needed for the photovoltaic system. The photovoltaic system, on the other hand, can support the heating even on cloudy days and still generate electricity in summer when the water is already warm.

i_b_n_a_n schrieb:

If the Munich startup with the Sion finally gets ready in three years... perfect.

By the time the thing finally arrives, it will already be "outdated" and too expensive. No "normal" person will want to buy something like that then.