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Home Battery Backup Sizing Calculator

Estimate home battery size for outage backup based on essential loads, runtime, inverter efficiency, and reserve margin.

Decision summary

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.

Get deeper options
Change these first: Essential Load, Backup Hours, Inverter Efficiency, Reserve Margin.
Watch these outputs: Base Energy Needed, Recommended Battery Size, Battery Modules Needed.
Sanity check: compare at least two scenarios before using the estimate for a quote, purchase, or planning decision.

How to use this result

What it is for

Use this energy calculator to compare scenarios before committing money, time, or a provider conversation.

Method

The estimate combines Essential Load, Backup Hours, Inverter Efficiency and returns Base Energy Needed, Recommended Battery Size, Battery Modules Needed.

Next step

If the result changes your decision, verify the current quote, rate, eligibility rule, or provider term before acting.

Home Battery Backup Sizing Calculator
Logic Verified
Configure parametersUpdated: Feb 2026
Transparent inputs
Change assumptions live
Decision support
Estimate first, verify quotes
0 - 100000
W
1 - 240
hours
1 - 100
%
0 - 200
%
0.1 - 100
kWh
0 - 100000
$

Base Energy Needed

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Recommended Battery Size

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Battery Modules Needed

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Estimated Installed Cost

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Assumptions used
These are the live inputs behind the result. Change one at a time before acting on the estimate.

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 $

Turn this result into a decision

Use the result to compare providers, request quotes, or send the scenario to a specialist when the numbers matter.

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Expert Analysis & Methodology

Use this Home Battery Backup Sizing Calculator to compare scenarios with transparent assumptions and instant outputs.

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Disclaimer

This calculator is provided for educational and informational purposes only. It does not constitute professional legal, financial, medical, or engineering advice. While we strive for accuracy, results are estimates based on the inputs provided and should not be relied upon for making significant decisions. Please consult a qualified professional (lawyer, accountant, doctor, etc.) to verify your specific situation. CalculateThis.ai disclaims any liability for damages resulting from the use of this tool.