About
Watt Sizing is an independent site of free calculators to size a generator or a battery: home backup in an outage, RV, medical device, food truck or jobsite.
Who runs the site
The site is published by an individual on a non-commercial basis who chose not to publish their name (French law allows this for non-professional publishers). No generator or battery brand funds the site or reviews the results.
Where the wattages come from
Wattages are typical values, cross-checked against wattage charts published by generator and appliance manufacturers. Each appliance was re-checked in November 2026; where no source gave a figure, the value remains an estimate. They are averages: the exact figure is on your appliance's rating label.
How the math works
We add up the running watts, add the single largest starting surge, then a 20% margin. For a battery, watts × hours of use, divided by 0.85 for losses. The full method is explained on the home page and on each calculator.
How the site is funded
Some product links may be affiliate links: we may earn a commission at no extra cost to you. The calculator result never depends on them. There are no ads, no cookies and no analytics.
Found a mistake?
If a value looks wrong, email contact@watt-sizing.com with the appliance model: we will check it and fix it.
Updated
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