Exotic combination: wood pellets + exhaust air heat pump? [fr]Combinaison exotique : granulés de bois + pompe à chaleur à air évacué ?[/fr] [hi]अजीब संयोजन: लकड़ी के पेललेट + निकासी वायु हीट पंप? [in]Kombinasi eksotik: pelet kayu + pompa panas udara buang? [zh]异国组合：木质颗粒 + 排气热泵？[/zh] [ru]Экзотическая комбинация: древесные пеллеты + вытяжной тепловой насос? [es]¿Combinación exótica: pellets de madera + bomba de calor de aire de escape?

I agree. With a new (matching the house) heating system and possibly a better ventilation concept, the current costs could possibly be halved.

The energy demand with a total of 13000 kWh per year is even very low and at new building level.

As I understand it, this is the pure electricity consumption for heating. 13000/270 = 48 kWh/m2.

This results in about 350 euros of electricity for heating per month, which fits with the household electricity and the 400 euro monthly electricity costs mentioned in the first post.

This is not new building level.

Since this concerns 3 heat pumps, a COP of about 2 can be conservatively assumed, which would be 26000 kWh of heat per year.

The fact that 3 heat pumps are working here alone already shows that something cannot be right with the concept.

As I understand it, this is the pure electricity consumption for heating.
13000/270 = 48 kWh/m2.

That means only for heating about 350 euros in electricity per month, which fits with household electricity costs of 400 euros per month mentioned in the first post.

This is not a new building level.

Since this concerns 3 heat pumps, one can conservatively estimate a COP of about 2, which would be 26000 kWh of heat per year.

The fact that 3 heat pumps are working here alone already shows that something might be wrong with the concept.

I seriously doubt that we have a COP of 2 here. Most of the time the exhaust air heat pump will heat directly electrically. I assume a real heating demand of maybe 16000 kWh hours.
But that doesn’t really matter, because due to the radiators and the given conditions, I still recommend gas. That doesn’t really make a difference, since the smallest gas heater I know has a maximum output of 9 or 11 kW. And we are certainly below that.

I thank everyone for the constructive contributions! Let's see how it turns out, the decision will be made this week

Keep us updated, I am looking forward to the solution.