HomeBackup & SolarInverter and Battery Combined Planner

Plan your backup power · Free calculator

Inverter and Battery Combined Planner

This calculator works out inverter capacity and battery Ah in one joined workflow. This joined workflow sizes peak power for the inverter and usable energy for backup duration as two related but separate results. Replace the example values with information from your own label, bill, drawing, product sheet or land record. Review the appliance list, motor surge, bank voltage and desired essential-load duration with a qualified installer. The formula and every editable assumption remain visible so the result can be checked before it is used for planning. Keep the values and result together when you compare or share this planning scenario.

Updated 17 July 2026Use for planningFormula and steps shown

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Your values

Every input includes a simple explanation.

Simple wordsFormula shownPrivate inputs

Simple viewUsing editable example assumptions for technical settings.

Running backup loadUser-entered value — example shownThe combined watts used after all connected appliances are running normally.

Desired backupUser-entered value — example shownThe number of hours represented by the field label in this calculator, such as daily use or desired backup time.

hours

Battery voltageManufacturer-specific value — example shownThe voltage printed on the battery or the total connected battery bank.

Private: calculations run in your browser. Saved scenarios, preferred electricity rate and land state stay on this device.

Your result

Required inverter capacity

1,125 VA

Use the load list and desired backup together; one does not determine the other.

Comparison range (±10%)1,013–1,238 VA

Running load500 W

Battery capacity estimate392.16 Ah

Desired backup4 h

How this was calculated

Formula used

Inverter VA uses peak load; battery Ah uses average load × backup time

Your values in the formula

500 W running × 150% surge = 750 W adjusted peak; 750 W ÷ 0.8 power factor × (1 + 20% margin) = 1,125 VA; battery = 392.16 Ah

Assumptions and rounding

The ±10% figure is a labelled comparison band around the calculated VA, not an extra formula input.
Starting surge, power factor, depth of discharge and losses are assumptions.

Use this as a planning range. Confirm continuous rating, peak rating and battery compatibility with the manufacturer and a qualified installer.

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How to use this calculator

Step 1. List only the appliances needed during a power cut and use their running watts.
Step 2. Start with the simple result, then open advanced assumptions for losses, surge and usable battery share.
Step 3. Check continuous and surge ratings, battery compatibility and safe installation with the product sheet or installer.

What can change the answer

Check these details

Motors and compressors can need extra power when they start.

Battery age, temperature and a high discharge rate can reduce delivered energy.

Use this as a planning range. Confirm continuous rating, peak rating and battery compatibility with the manufacturer and a qualified installer.

Understand your result

What this answer means

Read the meaning first, verify the important details, then avoid the most common planning error.

What it means

This joined workflow sizes peak power for the inverter and usable energy for backup duration as two related but separate results.

What to check next

Review the appliance list, motor surge, bank voltage and desired essential-load duration with a qualified installer.

Common mistake

Using the peak load for every backup hour can oversize batteries when high starting demand lasts only seconds.

Sources and method

Sources used for this calculator

Documented dimensional-analysis formulasGharGanit editorial methodologyFormulas are derived from units and expose every editable efficiency, density, dry-volume and wastage assumption. Reviewed 2026-07-16.Measures relating to safety and electric supply regulationsCentral Electricity Authority, Government of IndiaSupports the safety boundary shown on backup, inverter, pump and EV calculations; it is not used to invent equipment performance. Reviewed 2026-07-19.

Official verification links

Check the official context

These independent government and standards resources help you verify the inputs or decision. Inclusion is not an endorsement.

National Power PortalMinistry of Power, Government of IndiaUse the national portal for official power-sector data and reporting context.Open official resource PM Surya Ghar rooftop-solar portalGovernment of IndiaCheck the official residential rooftop-solar process, eligibility and portal services.Open official resource Grid-connected rooftop solar programmeMinistry of New and Renewable Energy, Government of IndiaRead official rooftop-solar programme context before making a project decision.Open official resource

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Learn before deciding

Useful next reading

Read the inverter and battery guide Understand 150 Ah backup time Compare watts, VA and Ah Explain lower real backup

Calculator revision

Version 1.1

Updated 17 July 2026. Changes listed here describe this calculator release; they are not invented historical entries.

Added category-specific instructions and default-value origin labels.
Added device-local scenario saving and a direct issue-report workflow.

Read the correction process