Home Battery Storage Calculator
Check whether a home battery pays off, with calculated savings and an honest cost assessment, entirely in your browser.
Your inputs are processed in your browser and are not transmitted to our servers. Note: third-party resources (e.g. advertising and analytics from Google/Cloudflare) and an optional PayPal donation link may transfer data when loading or when clicked. Browser extensions or plugins may be able to read content that is visible in the input fields.
The result will appear here …
Legal notice
Current as of: 11.08.2026.
The results reflect the legal and fiscal state as of the date stated above. They are provided for general information and initial guidance only. They are not individual financial, tax or legal advice, and no guarantee is given as to their accuracy, completeness or suitability for your circumstances. In particular, the results are not a substitute for an official or judicial assessment. Please check the information independently and seek qualified advice where appropriate, as you are solely responsible for any decision made in reliance on the result.
How to use this tool (video)
This video is hosted on YouTube. When you play it, data may be sent to Google.
Home battery calculator: is a storage system worth it?
Does a battery storage system really add value to your photovoltaic system? Our calculator estimates the additional self-consumed solar power, the annual savings and the total result over the service life. Let us be honest: without a battery, self-consumption on a typical system often sits at only 30 to 40 %, while a well-sized battery frequently lifts it to 60 to 80 %. Whether that pays off depends heavily on the electricity price, the battery cost and your consumption profile. Our calculator makes this trade-off visible with your own numbers. This page is not investment or tax advice.
How a battery affects profitability
Without a battery you can only use the solar power that is consumed at the moment it is generated. A home battery buffers surplus power and makes it available in the evening and at night when you need it. This raises your self-consumption and saves power you would otherwise buy at the full household price. But the battery itself costs money and has an efficiency below 100 %: some energy is lost on every charge and discharge cycle, and real round-trip efficiency is usually between 85 and 95 %. Then there is degradation, because the usable capacity of the cells declines over the years.
How the calculator works
The calculator assumes the battery makes an additional share of your PV generation usable, that is it raises your self-consumption. It values this additionally used energy at the household electricity price, deducts the round-trip efficiency and sums the saving over the service life with a moderate price escalation. Degradation is factored in across the years, since older cells store less and less. The result shows whether the saving covers the battery cost over time, or whether the value lies more in independence.
Sample calculation
A 10 kWh battery costing 6,000 euros (600 euros per kWh, a common 2026 price) raises the self-consumption of an 8,000 kWh system by 15 percentage points. With a power price of 37 cents and 90 % efficiency it saves about 400 euros in the first year. Over 15 years it covers its cost under these assumptions, with a payback of around 13 years. That is largely because battery prices fell sharply in 2026. The result depends heavily on the power price, self-consumption and purchase cost: pay more or use little yourself and there is often no return, the value then lies in independence and backup power. Good lithium iron phosphate batteries often reach 6,000 cycles or more under daily use, which is commonly 10 to 15 years.
Frequently asked questions
Is a battery storage financially worth it?
Usually only under favourable conditions: high power price, high self-consumption rate or low battery cost. Many households value independence and backup power more than the return. The calculator makes this trade-off transparent for your values.
What is the additional self-consumption from the battery?
It states by how many percentage points the battery raises your self-consumption. Example: without a battery 40 percent, with a battery 55 percent, so 15 percentage points more. The higher this value, the sooner the battery pays off.
What is round-trip efficiency?
Part of the energy is lost during charging and discharging. An efficiency of 90 percent means that of 10 kWh charged, only 9 can be used. The calculator accounts for this loss in the saving.
How long does a home battery last?
Depending on technology and cycles, typically 10 to 15 years, some much longer. After that the usable capacity often declines. You can choose the service life in the calculator to compare scenarios.
Is this a binding calculation?
No. Degradation, real cycles, prices and usage behaviour are uncertain. The calculator is a transparent estimate, not a substitute for advice. For precise planning, talk to an energy advisor or installer.
Are my data stored?
No. All calculations run 100 % locally in your browser. Your entries are neither sent to a server nor stored.
Read more about this tool
How exactly does the calculator work?
The calculator compares two scenarios: a PV system without a battery and the same system with one. For both it estimates how much of the generated power you use yourself. Without a battery, self-consumption in many households sits around 30 to 40 %, and with a well-sized battery it often rises to 60 to 80 %. Your entries move that number, so you can set the extra self-consumption directly in percentage points.
The saving comes only from the power the battery makes additionally usable. The calculator values that amount at the household electricity price and deducts the round-trip efficiency, that is the loss during charging and discharging. Over the service life it adds up the yearly saving and accounts for a moderate electricity price rise and for the capacity loss of the cells through degradation. As a result you see whether the accumulated saving reaches the purchase cost over the years, or whether a gap remains.
What really matters in practice
A home battery pays off financially only under certain conditions. The most important is a high electricity price, because the saving depends directly on what you would otherwise pay for grid power. Just as decisive is a high evening and overnight demand, since only then does the stored power actually get used. Add the purchase cost per kilowatt hour, which fell sharply in 2026: common 5 to 10 kWh batteries now often run from 300 to 700 euros per kWh, with a 2026 first-half market average of around 315 euros (as of 2026, manufacturer and installer figures). Feed-in tariffs are also low in Germany, so selling power instead of using it yourself brings far less out of each kilowatt hour.
Technically, cell quality matters. Good lithium iron phosphate batteries (LiFePO4) often reach 6,000 cycles or more under daily use before the usable capacity falls to about 80 %. That often equals a service life of 10 to 15 years. Real round-trip efficiency is usually between 85 and 95 %: of 10 kilowatt hours charged, only about 9 come back out. People who enjoy a battery usually do so through independence, backup power and the satisfaction of using more of their own energy, so in most cases not through a classic financial return.
Why everything stays in your browser
This calculator runs 100 % locally, right on your device. Your entries never leave your browser, there is no server request, no tracking and no storing of your values. That applies to every input, from the electricity price to the service life. You can safely close or reload the page, your data stays with you. The tool is meant to give an estimate and is not a substitute for individual advice from an energy advisor or installer, especially when funding, taxes or a specific purchase are involved.