LCOS calculator: the real cost of each kWh from a battery

This calculator compares two batteries on the kWh they deliver over their entire lifetime and, if you enter the prices, on the cost of each kWh delivered, i.e. the simplified LCOS. All you need is the datasheet: capacity, depth of discharge, efficiency, cycles and residual capacity at end of life. The preset profiles contain the parameters of Heiwit sodium-ion batteries and typical values for lithium batteries.

How to use it

1. Choose a profile for battery A and battery B, or choose “Custom” and enter the datasheet figures from your quote.
2. Check the nominal capacity. The comparison makes sense between batteries of the same size, but you can enter different capacities: the calculator also shows the kWh delivered per nominal kWh.
3. Read the result. The kWh delivered over the entire lifetime, the years needed to use up the cycles at the chosen rate, and the break-even price: how much less the battery that delivers fewer kWh would need to cost to have the same cost per kWh.
4. If you know the prices, enter them: you get the cost of each kWh delivered, in cents, and the percentage difference between the two batteries.

What it calculates

The calculator applies a single formula, which anyone can work out by hand:

kWh returned over the whole life = rated capacity × DoD × efficiency × cycles × (100% + remaining capacity at end of life) ÷ 2

The last factor is the average capacity of the battery between the start and end of its life, assuming linear degradation. Dividing the price by the kWh delivered gives the cost of each kWh, i.e. the simplified LCOS. The reasoning behind each factor, with examples, is explained in the guide LCOS: the real cost of every kWh a battery delivers.

The preset profiles

The Heiwit data are those declared for the two battery generations: the new one, with polyanionic cells, on sale from early 2027, and the one on sale today. The lithium values are typical of datasheets for domestic use and do not refer to a specific product.

Frequently asked questions

Where do I find the data to enter?

In the battery datasheet, usually in the rows “cycle life”, “depth of discharge” or “DoD”, “efficiency” or “round-trip efficiency” and “residual capacity at end of life” or “EOL”. If a figure is missing, ask the installer for it in writing.

Can I compare batteries of different capacities?

Yes. The calculator shows the kWh delivered over the entire lifetime and also the kWh delivered per nominal kWh, which do not depend on size. For the break-even price and the cost per kWh, the comparison is valid at any capacity, because it is always based on kWh delivered.

What happens if I change the cycles per day?

Only the estimated years to use up the cycles change, not the kWh delivered. A home battery does about one cycle a day. With time-of-use tariffs, electric car charging or irregular business consumption, it can reach two.

Is the result a quote?

No. It is an estimate based on manufacturers' declared data, useful for comparing two batteries on the same basis. It does not include installation, inverter, maintenance, ageing over time or the time value of money.

Methodological note

kWh delivered over lifetime = nominal capacity × depth of discharge × round-trip efficiency × cycle life × (100% + residual capacity at end of life) ÷ 2, with linear degradation. Simplified LCOS = price ÷ kWh delivered. Estimated years = cycles ÷ (cycles per day × 365). The calculation runs entirely in your browser: no data is sent to Heiwit. Updated October 2026.

More tools and in-depth articles in the collection of Heiwit guides and calculators. The reference battery for the systems is the 10 kWh Heiwit sodium-ion battery.