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Generator size calculator

Estimate the generator size you need from the wattages of your appliances.

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Need Total running watts, Recommended size (kW)? The Generator size calculator derives it from Appliance wattages (comma-separated) in one step. For instance, with Appliance wattages (comma-separated) = 1500, 700, 200, 100 it returns Total running watts = 2,500 and Recommended size (kW) = 3.125.

How to use it

  1. Enter your values: Appliance wattages (comma-separated).
  2. Read the result instantly: Total running watts, Recommended size (kW).

Frequently asked questions

How does the Generator size calculator work?

It takes Appliance wattages (comma-separated) and derives Total running watts and Recommended size (kW) from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

A single value: Appliance wattages (comma-separated). Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Appliance wattages (comma-separated) = 1500, 700, 200, 100, the calculator returns Total running watts = 2,500 and Recommended size (kW) = 3.125. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Appliance wattages (comma-separated) = 1500, 735, 220, 115 instead, Total running watts goes from 2,500 to 2,570 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Appliance wattages (comma-separated) = 1500, 700, Total running watts comes out at 2,200. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Putting a number on a bill: what an appliance costs to run, whether a solar array covers the load, and how much heating a room actually needs.

What is the most common mistake?

Confusing power with energy. A kilowatt is a rate and a kilowatt-hour is a quantity; a 2 kW heater on for half an hour uses 1 kWh, and only the second figure appears on a bill.

What is the difference between the Generator size calculator and the TV Size Calculator?

This one returns Total running watts and Recommended size (kW); the TV Size Calculator returns Recommended size and Minimum size. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Water Heater Size Calculator is the closest one after this: Estimate the recommended storage water heater capacity for your household size.

What else is worth having open alongside it?

Solar battery size calculator and Solar panel calculator — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
How-toWhat Size Generator Do I Need? Add Up Your Running and Starting WattsSize a generator by listing the appliances you must run, adding their running watts, and allowing headroom for the surge when motors start.How-toHow Many Amps Does an Appliance Draw?Divide the appliance wattage by the supply voltage to get the current in amps — the number that decides breaker size, wire, and what can share a circuit.How-toWhat Wire Gauge Do I Need?Pick wire size from the load current, run length, and allowed voltage drop — the amps decide the minimum cross-section, distance forces you thicker.How-toWhat Size Heater Do I Need? Sizing BTUs by Room and ClimateSize a heater from room area and your climate: a BTU-per-square-foot rule gives the heat output, with watts and kW for electric units.How-toWhat Size Solar Battery Do I Need? Sizing by Daily UseSize a solar battery from your daily energy use, the days of autonomy you want, and the battery's usable depth of discharge.ComparisonSolar Panels: the Self-Consumption Rate Decides the PaybackSince June 2026 a French rooftop is paid 1.1 cents for an exported kilowatt-hour and avoids 25.61 cents by consuming the same one. That ratio of 23 to 1 makes the self-consumption rate — the variable almost every quote omits — worth more than the amount of sun falling on the roof.