Calculation method

Indicative home battery savings

What a home battery yields depends heavily on how you use it and on your energy contract. This page shows the formula behind an indicative annual benefit, worked through with a transparent example, so you can see exactly which assumptions drive the outcome. It is a calculation aid, not a guarantee of return.

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The formula

We calculate the net annual benefit as follows. Every term is a figure you can look up in your own contract or meter data.

net annual benefit = E × P − (E / (R / 100)) × V − K

E delivered kWh after losses: The energy the battery actually delivers to your home in a year, after charging and discharging losses.
P purchase price: The price per kWh you would otherwise have paid for electricity from the grid, in euros.
V foregone export compensation: The compensation per kWh you give up by storing solar power instead of feeding it back to the grid.
R efficiency percent: Round-trip efficiency as a percentage, used to determine how much has to be charged in order to deliver E.
K annual additional costs: Any recurring costs such as a service plan or monitoring subscription, in euros per year.

Worked example

E = 1,000 kWh delivered per year
P = €0.30 per kWh
V = €0.08 per kWh
R = 90 % round-trip efficiency
K = €0 additional annual costs

Step 1 — value of stored energy:

1,000 × 0.30 = €300.00

Step 2 — energy charged (1,000 / 0.90) and foregone export:

1,111.11 × 0.08 = €88.89

Step 3 — net annual benefit:

300.00 − 88.89 − 0 = €211.11 per year

Simple payback with a €6,000 investment:

6,000 / 211.11 ≈ 28.4 years

What this calculation does not include

This is a simple annual model. It does not account for battery degradation over the years, the cost of eventual replacement, financing or interest, or seasonal variation in solar yield. It also assumes constant prices and tariffs. A real outcome will therefore differ — this is not a guarantee of return.

Run your own figures

The interactive calculator on the Dutch section lets you enter your own consumption, tariffs and system choice to get an indication. Treat the result as a starting point for a conversation with us.

Open interactive calculator (Dutch)

Discuss your assumptions

Send your consumption, tariff details and solar yield through the quote form. We will show what the figures mean for your situation and where the uncertainties lie.

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