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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 Austria

Regulation determines the limits and tariffs this calculator works with.

No guaranteed feed-in tariff — the price is negotiated

Austria has no equivalent of the German statutory tariff. What you receive for surplus is set by your electricity supplier.

Typical range
3–11 ct/kWh
Guarantee
none in law

This is the largest economic difference from Germany. The calculator works with an average — get a concrete offer before relying on it.

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Remuneration usually tracks the exchange price, sometimes at a discount, sometimes fixed for one or two years. It can change substantially when the contract ends — in either direction.

For the economics this means self-consumption counts for even more than in Germany. Sizing an array close to your own demand is more defensible here than there.

OeMAG's market premium offers a subsidised route for larger systems, but it is tied to tenders and rarely relevant for households.

Energy communities: the Austrian speciality

Surplus electricity can be passed directly to neighbours, at freely agreed prices and with reduced grid fees.

Grid fee discount
up to 57 % (local level)
Renewable energy community
same grid level
Citizen energy community
nationwide
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Austria implemented the EU rules on energy communities far more ambitiously than Germany. An operator can sell surplus to members of the community instead of releasing it at a low market price.

In practice this is the most effective answer to the missing feed-in tariff: instead of three to eleven cents, fifteen to twenty is often achievable within a community — and the buyer still pays less than to a supplier.

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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All results are model calculations based on your inputs and statistical reference data. They do not replace individual professional planning.

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