Solar Battery Size Calculator
Estimate a practical solar battery size from daily electricity use, the share used after sunset, backup reserve and system efficiency.
How the calculation works
Estimate a practical solar battery size from daily electricity use, the share used after sunset, backup reserve and system efficiency. Change every input to match your vehicle, equipment, tariff or measured consumption.
Worked example
A home using 18 kWh per day with 60% outside solar hours needs to shift about 10.8 kWh before reserves and losses.
What can change the result?
- Use smart-meter data to identify daytime and evening demand.
- Oversizing can leave capacity unused during low-solar months.
- Backup reserve reduces capacity available for daily solar shifting.
Frequently asked questions
Is the largest possible battery best?
Not necessarily. A battery that rarely fills or empties may deliver a weaker financial return.
Does this calculate off-grid autonomy?
No. It focuses on shifting solar energy within a typical day. Use the backup battery calculator for outages.
Should EV charging be included?
Include only the EV energy you intend the home battery to supply. Direct daytime solar charging may not need battery storage.
Use the result responsibly
This calculator is intended for comparison and planning. Verify equipment limits, tariffs and important electrical decisions with the manufacturer, energy supplier or a qualified professional.