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Amperecalc

Solar & storage

How much storage do you actually need?

Every additional kilowatt hour of storage delivers less than the one before it. This calculator draws the saturation curve for your system and marks the point where more capacity stops paying.

How we calculate

Calculation model

  1. 01

    For each month a typical daily profile of generation and load is built and simulated hour by hour.

  2. 02

    Surplus charges the battery up to its usable capacity, deficit discharges it — with round-trip efficiency and depth of discharge.

  3. 03

    The simulation is repeated for every capacity to trace the self-sufficiency curve.

  4. 04

    Economics follow from the storage cost per kilowatt hour cycled over the cycle life.

Good to know

  • Practical rule of thumb: about 1 kWh of usable capacity per 1,000 kWh of annual consumption, capped at the array size in kWp.
  • Usable capacity is not rated capacity — depending on the system there is 5 to 20 percent of reserve between them.
  • A battery raises self-sufficiency but lowers the return per euro invested compared with the array alone.

Law & subsidies

What applies in Switzerland

Regulation determines the limits and tariffs this calculator works with.

Export remuneration: every grid operator decides for itself

There is no national tariff. What you receive for exported electricity is set by your local utility — and the national spread is more than threefold.

Typical range
4–16 Rp./kWh
Set by
around 600 grid operators
National flat rate
does not exist

This is the single most consequential number in the whole calculation, and the one no calculator can know for you. Look up your utility's tariff before ordering a system.

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Two neighbouring municipalities can differ by ten centimes per kilowatt hour. On a typical system exporting 4,000 kWh that is 400 francs a year — over twenty years, more than the price of a battery.

Since the revision of the Energy Act a minimum price applies, based on avoided costs. It does not remove the spread, it only limits it from below.

In practice: where remuneration is high, a large array pays. Where it is low, almost only self-consumption counts — which moves storage and load shifting to the front of the queue.

Grouping for self-consumption (ZEV)

Several parties on one or neighbouring plots may group together and settle solar electricity internally.

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For apartment buildings this is the central lever: instead of releasing surplus at the low export tariff, the owner sells it to the tenants at a price that must sit below the grid tariff but may sit well above the export rate.

The grouping needs an internal metering concept and an agreement with the tenants; towards the grid operator it appears as a single customer.

This compilation is orientation, not legal advice. Rules in this field change several times a year — check the linked primary source before you invest, or ask a certified specialist.
See all regulatory topics

Frequent questions

Answered briefly.

Why doesn't self-sufficiency rise linearly with battery size?

A battery can only move one day's surplus into the night. Once it is large enough for the average night, extra capacity only helps on a few especially sunny days. The curve therefore saturates.

Can a battery make me fully self-sufficient?

Not on an annual basis. Winter demand cannot be covered by household-scale storage, because December yields roughly a tenth of June. Realistically, 55 to 80 percent self-sufficiency across the year.

What does a stored kilowatt hour cost me?

Storage price divided by cycles times usable capacity times efficiency. The calculator reports this figure directly — if it is below your electricity price, the battery pays.

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