ᐅ Should You Install a Photovoltaic Battery Storage System or Not?

Our new build is already quite advanced. Next week, 15 photovoltaic modules with a total output of 5.1 kWp will be installed. We are getting a heat pump with a capacity of 5.12 kWh. Initially, a battery storage system was not planned because we wanted to live in the house for at least one year to monitor our electricity consumption patterns, and then potentially add a battery or expand the photovoltaic system later. Now there is a new program that offers a 40% subsidy for battery storage—but only in connection with new builds. That sounds tempting. Should we go for it? What capacity should the battery have at a minimum? The condition is: "The ratio of system output to usable battery storage capacity must be at least 1.2 kWp to kWh of battery storage. Storage capacity exceeding this ratio is not eligible for funding." Have I understood correctly that only a battery with a capacity of 4.25 kWh would be eligible for funding?

Or is this all too small? Just “play equipment”?

Basically: save your money and please install as many modules on the roof as possible (ideally covering it fully). When it comes to the battery storage, it depends on your goals—whether you want high self-sufficiency or maximum return on investment. For the former, adding storage makes sense; for the latter, you need to run the numbers carefully. I’m not familiar with the 40% subsidy you mentioned, but in the cases I know, there was always a clause limiting feed-in to a maximum of 50% of the system’s output, which leads to significant energy loss.

Again, system size will benefit you much more than the battery because even in poor weather the basic yield is higher, plus you get better compensation. Also, always consider your electricity consumption over the next 10 years—if you plan to charge two electric vehicles using a system of around 5 kWp, that won’t be enough for long.

Storage systems are now worthwhile, even without subsidies. It was quite different two years ago. So go for it! A 40% grant is amazing.

I would first observe what your habits/consumption are like.
And I agree with the statement to install as much photovoltaic capacity on the roof as possible. Either just under 10 kWp to avoid the Renewable Energy Act surcharge or over approximately 12.5 kWp, since it is financially worthwhile despite the surcharge.
There is a specialized forum for this topic. It is quite elite but very knowledgeable.

I believe there are two options: whether to use a storage system or not.

My opinion:
If you want to be more independent from the grid and more self-sufficient, I would recommend using a storage system, even if it may not seem very practical right now (costs).

If you focus on the cost-benefit ratio and when the system will pay off, then I would choose a storage system as small as necessary (especially if it is going to be a KFW40+ house) and maximize the roof space as much as possible.

Heidi1965 schrieb:

There is now a new program that provides a 40% subsidy for energy storage systems, but only in connection with new construction.

Could you please say where this subsidy is available? I'm also personally interested. With a subsidy like that and no other drawbacks, it’s almost a must. But please make sure to cover the entire roof—that makes sense.