ᐅ Quote for photovoltaic system including battery storage – storage yes/no?

Hello everyone,

My wife and I are currently planning to build our single-family home of about 140 m2 (1,507 sq ft) and are considering whether to build it to KfW 40 standard or not (mainly for cost reasons). We have received an offer from our construction company for a photovoltaic system with 6 kWp and a high-voltage battery from Varta with 6.5 kWh (6.5 kWh) storage capacity, costing around 18,000 euros. Since the battery alone costs nearly 6,000 euros, and I recall reading here in the forum that many people reject a battery because a) it is too expensive and b) it would be better to invest in additional photovoltaic modules instead, I wanted to ask how you would approach this situation. The plan also includes installing an air-to-water heat pump with central, decentralized, or controlled mechanical ventilation (we are still considering these options as well).

1.) Would you remove the battery and replace it with more photovoltaic modules? If yes, how much kWp capacity would you recommend for a single-family home built to KfW 40/55 standard with "normal use," i.e., occasional home office?
2.) Or would you keep the battery and increase the photovoltaic system capacity with additional modules?

Do you have any other ideas or suggestions regarding what we should pay attention to in connection with the photovoltaic system?

Option 1: Fully utilize the roof and make use of all available surface areas

nordanney schrieb:

Option 1. Use the entire roof and maximize all available space

Hello nordanney,

thank you for your feedback. By "use the entire roof," do you mean maximizing the suitable roof area? And can you give me a rough estimate of how many kW peak would be needed for our house? Are we talking about 9, 12, or 15 kW peak?

haus_bau2025 schrieb:

And can you tell me approximately how many kWp would be needed for our house, roughly speaking?

You need as much as your roof area allows and your budget permits.

We have a 13 kWp photovoltaic system with a 9.6 kWh battery storage for 22,000 euros,
your builder is charging excessive prices.
So now build without photovoltaic and subcontract the photovoltaic separately, the prices for photovoltaic are falling.

haus_bau2025 schrieb:

Are we talking about 9, 12, or 15 kW peak (kWp)?

Our 13 kWp system supplies about 2,500 kWh of household electricity and 2,500 kWh for the heat pump.
The calculation model predicts a monthly residual electricity bill of €6.