Use our home battery backup sizing calculator to work out base energy needed. Enter essential load and backup hours — results update instantly.
Formula
const baseKwh = essentialLoadWatts * backupHours / 1000; const adjustedKwh = baseKwh / (inverterEfficiency / 100) * (1 + reserveMargin / 100); const batteriesNeeded = batteryModuleKwh > 0 ? Math.ceil(adjustedKwh / batteryModuleKwh) : 0; const estimatedCost = batteriesNeeded * costPerModule; return { baseKwh, adjustedKwh, batteriesNeeded, estimatedCost };Essential Load
1,200 W
Backup Hours
12 hours
Inverter Efficiency
92 %
Reserve Margin
20 %
Battery Module Size
5 kWh
Installed Cost / Module
4,500 $
Use the result to compare providers, request quotes, or send the scenario to a specialist when the numbers matter.
Home Battery Backup Sizing Calculator estimates Base Energy Needed, Recommended Battery Size, Battery Modules Needed, Estimated Installed Cost from Essential Load, Backup Hours, Inverter Efficiency, Reserve Margin, Battery Module Size. It is built for solar, battery, heat pump, EV charging, and quote-comparison decisions; use the output as a decision checkpoint, then confirm current pricing, rules, quotes, or professional advice before committing money.
Use this energy calculator to compare scenarios before committing money, time, or a provider conversation.
The estimate combines Essential Load, Backup Hours, Inverter Efficiency and returns Base Energy Needed, Recommended Battery Size, Battery Modules Needed.
If the result changes your decision, verify the current quote, rate, eligibility rule, or provider term before acting.
Founding provider slot
We are opening one clearly labelled sponsor slot per high-intent calculator/category. The test offer is $49 USD for a 30-day tracked placement, with opt-in leads only and no anonymous views sold as leads.
Spot an error or need an update? Let us know
This calculator is provided for educational and informational purposes only. It does not constitute professional legal, financial, medical, or engineering advice. Results are estimates based on the inputs provided and should not be relied upon for making significant decisions. Consult a qualified professional to verify your specific situation. CalculateThis.ai disclaims any liability for damages resulting from the use of this tool.
Reviewed by the CalculateThis.ai editorial team. Updates: check back for latest parameters. Tools are for estimation only — verify with current provider terms.