Inverter Size Calculator — Right kVA for Your Load, 2026

Enter your total running load and your biggest motor appliance. We'll size continuous and surge capacity and round up to a standard inverter size.

⏱ ~20 sec🔌 Handles motor surge🔒 No signup
Sum of everything running at the same time — lights, fans, TV, fridge, router…
Fridge, AC, well pump — whichever draws the biggest running watts

Recommended inverter

3 kVA
Standard size to buy
Continuous load needed2,640 W
Surge load needed3,000 W
Required kVA (with margin)3.3 kVA

Standard sizes shown: 1, 1.5, 2, 3, 3.5, 5, 6, 8, 10, 12, 15, 20 kVA. Always round up, never down.

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How inverter sizing works

Continuous need (W) = Running load × (1 + Safety margin)
Surge need (W) = (Running load − Motor load) + Motor load × Surge multiplier
Required kVA = max(Continuous, Surge) ÷ Power factor ÷ 1000

Inverters are usually the component people undersize, because a spec sheet's "peak power" figure looks generous until a fridge and an air conditioner try to start at the same moment. Sizing for surge — not just running watts — is what keeps the inverter from tripping.

Frequently asked questions

Should I size the inverter to match my battery or my panels?

Neither directly — size it to your load. Then check it against your battery's max continuous discharge rating and your array's peak output so none of the three components bottleneck the others.

What's a safe safety margin?

20-25% is standard. It leaves headroom for adding appliances later and for the modest efficiency loss inverters have as they approach full rated output.

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