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    Home battery payback calculator

    Work out with the last 12 months' real electricity prices how much a home battery would save a year and whether it pays for itself before its warranty ends.

    Energy
    Your last 12 months' consumption is in the network company's self-service or on your bill. The buttons below are typical examples.
    More at night means night hours weigh twice as much (electric heating, charging a car at night). Across the months the use is spread evenly.
    Battery
    All the battery and its installation cost, with VAT.
    More about the battery
    How much of the capacity the battery really uses. Usually 90 to 95 %.
    How much the battery can charge or give back in an hour.
    The round-trip efficiency of charging and discharging. Usually 85 to 92 % for a lithium battery.
    The seller's charge on top of the spot price, with VAT. With a fixed contract it is used to compare with the spot price.
    Network company and product

    All prices with VAT, as on a bill or an offer.

    Enter your yearly consumption and the battery's capacity and press Calculate.

    Results are informational. Calculation is based on your input and public rules, official accounting may differ. For accuracy, confirm the final result if needed from the appropriate official source or specialist. See the terms of use.

    How it works?

    The calculator takes the last 12 complete months of hourly prices in your area and adds to every hour the network charge, taxes, the seller's margin and VAT, because a battery saves the whole price of each kWh it replaces and pays the whole price of each kWh it takes.

    Every day it looks for the best cycle: the battery charges in the cheaper hours and gives the energy back in the dearer hours after them. It can give back only what the home uses in those hours, and at most its power in an hour. Charging and discharging lose part of the energy (efficiency). On a day when no cycle pays, the battery rests.

    The payback time is the battery's price less a subsidy divided by the yearly saving. Selling to the grid, reserve markets and solar panels are not in the calculation.

    Frequently asked questions

    Why is the saving so small?

    A battery only wins the difference between a cheap and a dear hour, and only as much energy as the home uses in the dear hours. Losses take part of the gain. With a difference of a few cents and a small use, the yearly saving stays at a few hundred euros.

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    What helps a battery pay for itself sooner?

    More use in the dear hours, a network product with a time tariff (a cheaper night charge), a larger price difference and a subsidy. With solar panels a battery also stores what they produce by day, which the calculator does not count yet.

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    Can the battery sell electricity to the grid?

    The calculation assumes the battery covers the home's own use only. Selling to the grid and reserve markets (frequency reserves through an aggregator, for example) can bring more, but that depends on the contract and the market and is not calculated here.

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    How accurate is the result?

    The prices are real, the use is an estimate by the profile you choose. The calculation uses hourly average prices and one cycle a day, and does not count charging the evening before. It cannot know how the battery ages or future prices.

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    What do efficiency and cycles mean?

    Efficiency is the share of the charged energy that comes back. A cycle is one full charge and discharge. If a battery goes through 300 cycles a year and the maker promises 6000, the cycles last 20 years, but the battery also ages with time.

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