ᐅ Photovoltaic System and Air-to-Water Heat Pump – Profitability for a Single-Family Home Built to KfW 55 Energy Efficiency Standard

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. 🙂

Maxwell8 schrieb:

> From a profitability perspective, does a photovoltaic system make sense for our situation?

A photovoltaic system of around 10 kWp or more makes sense today, even with low feed-in tariffs, when combined with self-consumption. You can easily calculate online what fits on your roof and what yields to expect.

Maxwell8 schrieb:

> What size and costs should we expect?

The bigger, the better. Around €1,100–1,200 per kWp net. If you already have scaffolding on your house that the solar installers can use, even better, as it lowers costs.

Maxwell8 schrieb:

> Should the system be installed directly on the roof or should preparatory measures like empty conduit pipes be arranged first?

Directly on the roof.

Maxwell8 schrieb:

We also have an attached 6x6m (20x20 ft) flat-roof garage on the east side. Would adding photovoltaics there also make sense?

Have it calculated. It can make sense in terms of increasing self-consumption.

Maxwell8 schrieb:

We would need to finance the photovoltaic system, as there is no sufficient budget left.

Consider taking a €15,000 loan for a larger system. With a maximum interest rate of 1.5% and 4% repayment (check the actual conditions with your development bank or lender), that’s roughly €825 per year. Revenue from feed-in tariff alone, assuming about 10,000 kWh produced electricity, is around €650 per year, plus self-consumption savings on 2,000 kWh equaling roughly €300. So the system will pay for itself after taxes, and this is a fairly conservative estimate.

Maxwell8 schrieb:

Hello,

we are building a fairly large KFW55EE house with external dimensions of about 10x14m (33x46 feet) and a roof pitch of 15° (roof slopes facing north and south).
We have a lot of window area (100m2 (1,076 sq ft)) and expect an energy consumption of 7,000 to 9,000 kWh per year due to the size.
Heating is provided by underfloor heating with the Tecalor THZ 504 air-to-water heat pump.

The feed-in tariff is no longer significant, but the current electricity price is 45 cents per kWh.
We would need to finance the photovoltaic system ourselves as there is no sufficient budget available.

> Does installing a photovoltaic system make sense economically with our setup?
> What size and costs should we expect?
> Should it be installed directly or should we first prepare with empty conduits?
> We also have an attached 6x6m (20x20 feet) flat-roof garage on the east side. Would it make sense to add photovoltaics there as well?

I will of course speak with companies, but I would like to get some opinions beforehand.

Thanks in advance. 🙂

It definitely makes sense. Do you have air conditioning installed in the house? If so, it makes even more sense because when you want to cool, that’s when the most electricity is produced. What about a wall box (electric vehicle charging station)?

Thanks for the responses, sounds good.
No heat pump, but ventilation is planned. A charging station will also be installed in the garage; hopefully, the KfW subsidy will be available again. However, I can charge at work for free.
Bidirectional would be nice, as then I would have a 60+kWh battery, but the chargers are still way too expensive. 😉

Maxwell8 schrieb:

Thanks for the answers, sounds good.
No air conditioning, but ventilation yes. A charging station will also be installed in the garage; hopefully, the government subsidy will be available again. But I can charge for free at work.
Bidirectional charging would be nice, then I would have a 60+kWh battery, but the chargers are still way too expensive. 😉

The topic of bidirectional charging is really the question. If your battery is empty every day and you have to recharge it daily, how long will it last? I was also excited about something like that until I was informed otherwise.

Legitimate question. Due to my job, I change vehicles every few months, so there should not be significant effects per vehicle. It is also questionable whether manufacturer battery warranties, for example 6-10 years (applicable for over 25% capacity loss), apply in such cases or if they are excluded due to maximum charge cycles.