ᐅ Is it still worthwhile to install a solar thermal system when you already have an air-to-water heat pump and photovoltaic panels?

Hello everyone,

We are planning to install a photovoltaic system on the fully south-facing pitched roof of our planned house. Since we also want underfloor heating, an air-to-water heat pump is currently our preferred heating option.

I have read here in the forum that with an air-to-water heat pump, a solar thermal system— which heats water using solar energy—would be unnecessary. In other words, on sunny days, the air-to-water heat pump powered by photovoltaic electricity heats the water more efficiently and cost-effectively, right?

Is this still the current understanding as of 2019, so that with a photovoltaic system plus an air-to-water heat pump, the roof is covered only with photovoltaic panels instead of leaving space for a solar thermal system? How did you approach this?

Thanks in advance and have a great start to the week,
ludwig88sta

P.S.: Side question: if you plan a photovoltaic system on the entire south-facing roof, what type of roof tiles do you use? Naturally, as affordable as possible. What do you think about photovoltaic roof tiles (tiles with integrated photovoltaic modules)? Probably more expensive than installing regular photovoltaic panels on a tiled roof, right?

A solar (water) system is always pointless; it is only installed to be allowed to install a gas heating system. Therefore, yes, photovoltaic plus heat pump is good and sufficient.

Lumpi_LE schrieb:

A solar (water) system is always nonsense; it is only installed in order to be allowed to install a gas boiler.

Thank you.
Is the solar system somehow linked to the gas boiler, like according to KfW requirements or something?

Basically: you are not allowed to supply your house (Energy Saving Ordinance) solely with fossil fuels, so the gas heating system is most often supplemented with a solar thermal system.

The domestic hot water circuit, which requires a significantly higher supply temperature than the 30°C (86°F) needed for the underfloor heating, is heated to about 60°C (140°F) for showering by another heat pump – the hot water heat pump. This unit is powered by the warm indoor air and is installed in the basement or utility room. Ideally, it operates during the daytime using self-generated photovoltaic electricity, right?

No, the text refers to a domestic hot water heat pump. However, this is unnecessary if you already have a heat pump for heating. A standard heat pump can also heat domestic hot water and, as far as I know, even more efficiently than dedicated domestic hot water heat pumps.
Domestic hot water heat pumps extract heat from the building, which the heat pump then has to provide additionally for heating, at least during winter.

Solar thermal systems are always pointless.
Photovoltaics make financial sense even without heating; you shouldn’t mentally lump them together, although they complement a heat pump well.

Do not connect the heat pump to a separate electricity meter, so avoid a special heat pump tariff. The photovoltaic system automatically supplies all household consumers, including the heat pump. You can program domestic hot water production during the day in summer. This way, for more than six months a year, you produce domestic hot water with electricity from your own roof on 95% of the days.