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Inverter Size Calculator

Find what size inverter you need by ticking the loads that run at the same time. The calculator sizes on both numbers that matter — the continuous watts plus headroom, and the single largest starting surge against the inverter's peak rating — then shows the DC amps your battery cable and fuse must carry at 12, 24, or 48 V.

What runs at the same time?

W

Tick only what is on simultaneously. Motors and compressors show their starting surge; the inverter's peak rating (about 2× continuous on most units) has to clear the largest one.

Recommended inverter

2,000 W

continuous, pure sine wave · peak ≥ 4,000 W

Continuous, all on
1,410 W
With 25% headroom
1,763 W
Largest surge (refrigerator)
800 W
Sized by
continuous load
At 12 V this inverter pulls about 185 A DC from the battery at full rated load (163 A at your loads) — the cable and fuse between battery and inverter must carry that.

Typical load values; check the labels on your own appliances. Peak ratings and how long they hold vary by model, and an oversized inverter wastes battery on idle draw — size for your real peak plus headroom.

Frequently asked questions

Add the continuous watts of everything you will run at the same time, then check that your single largest starting surge fits inside the inverter's peak rating. Add 20–25% headroom to the continuous figure. A typical RV or small off-grid setup running a fridge, lights, laptop, and a few outlets lands on a 2,000 W inverter; a setup that has to start a well pump or an air conditioner is sized on the surge, which usually means 3,000 W or more.

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Rather not wire an inverter to a battery bank? A portable power station bundles the inverter, battery, and charger in one box, rated in the same continuous and surge watts. See the portable power station picks.

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Sources & standards

This tool's methodology and data follow US standards and authoritative public datasets: