Disclaimer and terms of use

What this site is

The calculators here are for learning and for a quick order-of-magnitude estimate. Every result shows the assumptions behind it, and every figure that comes from outside carries its source.

The site is free of charge and requires no account. All you need is a current browser with JavaScript enabled; once loaded, the calculators also work without an internet connection.

A result is only as good as what you put in. The ready-made appliance profiles are values typical for a category, or figures for one named model — never figures for your particular unit. Always overwrite them with the values from your own rating plate and the manufacturer documentation.

What this site does not replace

It does not replace an electrical installation design, the selection of protective devices, earthing, a transfer switch, or the inspection of completed work. It does not replace the documentation of your battery, inverter, charger or any other device; where the two disagree, the manufacturer documentation applies and our result does not.

It also does not replace the rules in force where you live. Connecting a backup supply to a house installation, working on fixed wiring and working on live equipment require qualifications in many countries, and often notification or inspection as well. Check what applies to you before you do anything.

If you are unsure whether you are allowed to do a job yourself, that is the signal to ask a qualified electrician.

Safety

Electricity kills, and batteries can injure you even at low voltage. Short-circuiting a lithium cell or a lead-acid battery delivers hundreds of amps, melts tools and starts fires. Lead-acid batteries give off hydrogen, which is explosive. A damaged lithium cell can ignite on its own and will not go out when you disconnect the supply.

Do not work on a live installation. Do not size cables and protective devices from a calculator alone. Do not connect batteries of different type, age or capacity together.

This site is not a guide to carrying out electrical work and does not describe the safety procedures such work requires.

Liability

We provide this site in the shape described above: as a free estimating tool, not as a design or as advice for a specific installation. We take care to keep the calculations correct and the figures sourced, but we do not promise that a result is fit for any purpose beyond that description.

To the extent permitted by law, we accept no liability for financial loss arising from reliance on the results of this site contrary to the reservations above — in particular damage to equipment, loss of supply, or the consequences of a purchase decision. Checking a result against the manufacturer documentation and with a qualified person is up to you; that is why we show the assumptions and the sources.

Nothing in this document is to be read as excluding or limiting liability for death or personal injury, for damage caused intentionally, or any other liability that cannot be excluded. Nor does this document limit any rights you have as a consumer under the mandatory rules of the country where you normally live.

Errors and feedback

If you find a mistake in a calculation, in an explanation or in a source — or want to make a complaint about how the site works — write to info@batterycalcs.com. Say what the report concerns and on which page. We reply within 14 days. The identity of the service provider is stated in the privacy policy.

The content of this site and of this document may change; changes are published on this page. This document was last updated on 22 August 2026.