How to use the Battery Backup Calculator
- Enter your values. Fill in Battery Capacity, Battery Voltage, Number of Batteries, Connected Load, Inverter Efficiency and Usable Depth of Discharge. Example values are pre-filled so you can see how it works.
- Get instant results. Results update automatically as you type — no need to press anything (or click Calculate).
- Review the breakdown. Check the detailed results, charts and tables below the main answer.
- Save or share. Copy the result, print it, or use “Share link” to send the exact calculation to someone.
About this tool
Electricity cost, solar, inverter, battery, wire size and appliance power calculators.
Read the complete Battery Backup Calculator guide
Frequently asked questions
Is the Battery Backup Calculator free to use?
Yes. The Battery Backup Calculator on Gemma-4 is 100% free with no sign-up, no limits and no watermark. An optional free account lets you save favourites.
Is my data private?
Yes. Your inputs are processed instantly and are not stored on our servers.
Does it work on mobile phones?
Absolutely. The Battery Backup Calculator is fully responsive and works on Android, iPhone, tablets and desktop browsers such as Chrome, Edge, Safari and Firefox.
What formula does the Battery Backup Calculator use?
It uses: Backup (h) = Ah × V × DoD × efficiency / Load (W). All calculations run with full precision and are rounded only for display.
How accurate is the Battery Backup Calculator?
The calculator uses standard, well-established formulas and exact arithmetic. Results are as accurate as the values you enter; for financial, medical or legal decisions, confirm with a qualified professional.
Who is the Battery Backup Calculator useful for?
It is popular with households trying to cut electricity bills, solar and inverter buyers, electricians and electrical engineers — anyone who needs quick, reliable help with power, energy and electricity cost decisions.