Sump pump backup

Estimate backup power for a sump pump.

Estimate battery watt-hours from pump runtime plus inverter idle draw, then check the separate continuous and startup output your backup source must provide.

Quick resultRun estimate

Battery capacity and inverter output are separate sump-pump checks.

Inputs

Planning assumptions

Pump running wattsUse pump specs or measured draw.Minutes running per hourHeavy rain can change this number quickly.Outage hoursHow long the backup needs to cover.Pump startup wattsUse a measured or manufacturer value; it should not be below running watts.Inverter idle wattsBattery-side fixed draw while AC output stays on for the full outage; use zero only when that overhead is truly absent.Inverter efficiency percentAC conversion loss used only in the battery Wh estimate.Battery reserve percentNameplate capacity left unused for headroom and aging.

Use this as a planning estimate

Small solar and backup-power estimates depend on real device draw, temperature, battery age, sun, shade, and product limits. Use the result to narrow a shopping range, then verify exact specs before buying.

Planning notes

What this calculator is checking

Capacity

Runtime and fixed overhead determine battery Wh

Pump energy is adjusted for inverter efficiency, while battery-side inverter idle watts are applied across the full outage before battery reserve.

Output

Starting the pump is a separate test

A battery may have enough watt-hours but still fail if the inverter cannot supply the pump's continuous or startup watts.

Risk

Water damage changes the standard

For critical basement protection, use this only as an early sizing estimate and have the complete backup design reviewed.

Solar recharge time calculator

Check whether a panel can refill the battery within your usable sun window.

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