ᐅ Supplemental Heating with an Air-to-Water Heat Pump and Solar Power System?

Hello everyone,

After initially focusing on a gas condensing boiler and a ventilation system for a long time, we are now reconsidering whether another heating option might be better.

The additional cost for an air-to-water heat pump is lower than the price for a gas condensing boiler plus underfloor heating, ventilation system, and gas pipeline with one house provider since the standard package already includes underfloor heating and the ventilation system. So far, so good.

Now we want to discuss this scenario again with our current favorite, Okal House. With this provider, we would also consider adding the “solar power plant” – a photovoltaic system with battery storage.

My question is: With a combination of an air-to-water heat pump, a ventilation system with heat recovery, and the solar power plant, would it still be necessary to use electric heating at any point? We live in the Rhine region, where temperatures are among the mildest in Germany – it is rare for temperatures to drop below 15°C (59°F), if at all.

The house will be a simple single-family home with 1.5 floors and about 150 m² (1,615 sq ft). We currently live here as two people.

Thank you very much for your help – additional tips that could make our decision easier are also welcome.

Best regards,
Jeanette

Heating with electricity?
Whether your electric heating element in the air-to-water heat pump activates depends on the outdoor temperature.
To run the entire system, including the ventilation unit and heat recovery, operational electricity is required. If your photovoltaic system produces little electricity in winter due to clouds, fog, or darkness and your battery storage is empty, you will need to buy electricity for the heating system!
Depending on the size of the storage and the photovoltaic system, it can also operate completely independently...

If I were to choose, I would rather combine solar thermal energy, which—unlike solar electricity—is not solely dependent on sunlight but also works with ambient heat from the air, for example (though naturally not as efficiently as the sun itself).

Illo77 schrieb:
If anything, I would rather combine a solar thermal system, which unlike solar electricity doesn’t rely solely on direct sunlight but also works with ambient heat from the air, for example (of course, not as efficiently as direct sunlight)

Solar thermal systems, however, can only produce hot water. What use is it if you generate hot water from ambient heat — which I doubt produces significant yield often, especially in winter — at relatively high investment costs, but in summer you only produce hot water instead of using the generated electricity to power your stove, washing machine, and other appliances?

Unfortunately, the sun shines mostly when you need little or no heating water.

Besides, solar thermal requires a large storage tank, which also needs to be kept warm when there’s no sun — often with electricity — and then heated again when the sun is out...

Hello,

We have installed an air-to-water heat pump (including hot water and ventilation) and an air heat pump (for underfloor heating). Additionally, we have a 6 kWp photovoltaic system (split 50% on the south and west sides).

The house size is 171 m² (1840 ft²) over two full floors.
Including the compensation from the utility company (13.4¢/kWp), our heating and hot water costs in the first year of operation were around 15–20 € per month (two-person household).

However, this low cost is only achievable through intelligent system control.
There are many factors to consider that a layperson might not be aware of, and even heating engineers and electricians find it challenging because the trades are not closely integrated.

If you want more information, just send me a private message.

Best regards,

Amin

We live in a cold region, and in our household of four, we have heating and hot water costs of 50 € per month using a ground-source heat pump and controlled mechanical ventilation.

This shows that absolute figures are not very meaningful since the buildings and conditions are not known or comparable.

@ Jeanette: In my opinion, especially for you living in the warmest part of Germany, an air-to-water heat pump is sufficient—possibly combined with controlled mechanical ventilation for comfort reasons, as proper ventilation is not always ensured in modern houses with busy occupants.

Solar thermal systems: the additional investment will never pay off. Here, winter yields are low anyway, and you also need a buffer tank, which significantly reduces the efficiency of the air-to-water heat pump. In summer, the 1–2 kWh per day needed for hot water does not justify a solar thermal system.

Photovoltaics: unvarnished calculations show it is hardly profitable anymore, especially if externally financed. Solar installers and new PV owners often present overly optimistic figures. A battery storage system is a good idea, but batteries are still very expensive and their lifespan is limited. Economically, it is certainly not profitable.

The most cost-effective and efficient solution for your situation is simply an air-to-water heat pump. This is my opinion based on the information provided here.

@ Elektro1: An air heating system and, in addition, an air-to-water heat pump? Two heat generation systems?
In which climate zone is your house located, and how is it insulated? What is your actual heat demand and consumption?