- Without a battery you usually cover only about 30 % of your consumption with solar power, with a battery it is often 60 to 70 %.
- Every kilowatt hour you store saves you around 27 ct (35 ct grid electricity minus 7.7 ct feed-in tariff).
- A battery pays off especially with high consumption, for example with an e-car or heat pump.
- Rule of thumb for the size: around 1 kWh of storage per 1,000 kWh of annual consumption.
Almost everyone who thinks about a solar system also asks about a battery. Many providers sell one automatically. We prefer to show honestly when it really pays off – and when it doesn’t.
Why a battery makes sense at all
The sun delivers most power at midday. Most households, however, need it in the morning and evening: cooking, washing, lights, TV. Without a battery, the midday power flows into the grid for little money, and in the evening you buy expensive power back.
The battery stores the surplus from the day and releases it in the evening. That way you use much more of your own power.
The honest calculation
How much a battery brings depends mainly on how much electricity you use. The table shows three typical households with a suitable solar system:
| Household | Suitable battery | More own power thanks to the battery | Benefit per year | Battery pays for itself after |
|---|---|---|---|---|
| 2 people, 3,500 kWh | approx. 5 kWh (€1,600–2,300) | approx. 1,200 kWh | approx. €330 | approx. 5–7 years |
| 4 people, 4,500 kWh | approx. 6 kWh (€1,900–2,700) | approx. 1,580 kWh | approx. €430 | approx. 5–6 years |
| 4 people + e-car, 7,000 kWh | approx. 8 kWh (€2,600–3,600) | approx. 2,450 kWh | approx. €670 | approx. 4–5 years |
The result: the higher your consumption, the faster the battery pays off. The right size matters – a battery that is rarely full only costs money. Modern LFP batteries last 6,000 to 8,000 charge cycles depending on the model. The batteries we install come with a 10-year warranty.
Besides the money, many customers also value the good feeling: with a battery you are more independent of your supplier and future price increases in the evening.
In the roof check you can compare both – with one click.
How big should the battery be?
Bigger is not automatically better. A battery that is too big hardly fills up in winter and costs unnecessary money. As a rule of thumb:
- Around 1 kWh of storage per 1,000 kWh of annual consumption
- So for a family using 4,500 kWh about 5 to 8 kWh
- With an e-car or heat pump rather 10 kWh and more
We use Solplanet batteries: the Ai-HB series with up to 20 kWh and the AP series with up to 50 kWh. So the size fits your household – and you can start small and add more later.
Adding a battery later – is that possible?
Yes. If you already have a solar system, we can add a battery in most cases. How much work that is depends on your existing inverter. Simply send us a photo of the type plate – we will quickly tell you what is possible.
Backup power: what happens during a power cut?
Many people think that with a battery they automatically have power during a power cut. That is not always true. Normal systems switch off for safety reasons when the grid fails. Backup power needs a suitable inverter and a corresponding installation.
Our hybrid inverter has a backup power function. Whether and how we set it up for you, we discuss in the consultation.
Conclusion
A battery is not a must, but it makes sense for many households – especially with higher consumption. We only recommend it if it suits you. And if you are still unsure: a battery can also be added later.
Frequently asked questions about batteries
How long does a battery last?
Modern lithium iron phosphate (LFP) batteries usually last 15 years and longer. Manufacturers usually give a 10-year warranty.
Do I need a battery for a wallbox?
No. You can also charge your e-car directly with solar power if it is at home during the day. A battery helps if you mostly charge in the evening.
Can I enlarge the battery later?
With many modern batteries, yes. Our standard battery can be expanded in modules.
As of: November 2026. All prices are guide values including installation. Legal and tax information without guarantee – the laws in force apply (including UStG, EStG, EEG).
