Why do some appliances change wattage between the US and Europe, and some don’t?
Power basics Updated 2026-08-09
It depends on where the constraint that actually sets the number lives, not on what kind of appliance it is. A kettle’s wattage is set by what the wall permits, so a US build and a European build of the same jug carry two different ratings. A home oxygen concentrator’s wattage is set by the compressor’s own fixed job, so it barely moves between the two markets at all.
An aquarium heater goes further still: its wattage is set by the tank it is built for, which has nothing to do with mains voltage, so the identical rating serves the identical size tank on both sides of the Atlantic — the opposite pattern from the kettle, on an appliance just as ordinary.
Same appliance, same category — does the number travel?
This library holds four appliance records sourced separately for a US and a European build, each from the manufacturer’s own documents rather than derived from one another — a kettle, a home oxygen concentrator, an aquarium heater and its air pump. Reading the two market figures side by side on each one is what makes it possible to compare the pattern directly instead of guessing from the appliance category.
When the wall decides: the electric kettle
Electric kettle, by region
The same 1.7-litre job, built to two different mains ceilings. Both figures are the manufacturer’s own rating-plate value, not a circuit limit dressed up as an appliance figure.
Official specverified 2026-08-08electric kettle record · US + EU
Twice the wattage for the same size jug, and the reason sits at the wall rather than in the kettle: what a US kitchen circuit is built to carry differs from what a UK ring and fused plug allow, and manufacturers rate each build to fit its own market’s ceiling. The full circuit-code arithmetic behind that ceiling is worked in this library’s kitchen-appliances article, which goes deeper into this one record than this page needs to.
When the device’s own job decides: the oxygen concentrator
Home oxygen concentrator, by region
A 5 LPM machine on each side of the Atlantic. The mains voltage behind these two very nearly doubles; the wattage barely moves.
Official specverified 2026-08-08oxygen concentrator record · US + EU
A difference of about 0.6% — close enough to flat that the mains standard reads as almost irrelevant. The compressor inside is doing the same amount of gas-separation work regardless of which wall it is plugged into, and it is that work — not the voltage supplying it — that sets the wattage. A kettle turns electricity directly into heat, so whatever the circuit allows, the kettle draws; a compressor has its own mechanical job to do first; the wall is upstream of the job, not equal to it.
When the object being acted on decides: the aquarium heater and its air pump
Aquarium heater, by region
The same wattage rating, from two different manufacturers on two different mains standards, both sized for roughly the same tank.
Rated by the maker for a 15–40 US-gallon tank.
See the record →A different manufacturer, a different mains standard, rated for roughly the same tank.
Official specverified 2026-08-09aquarium heater record · US + EU
Not close — identical. A heater’s wattage is set by how much heat the tank on the other end of the cord loses to the room, a property of the water and the glass, and mains voltage has no part in that equation. Buying a bigger heater than a tank needs is not the efficient choice either: an undersized heater does not draw less power, it simply runs a higher fraction of the time trying to reach the same set temperature.
Its air pump, by region
The same story from a second product in the same category, on a smaller number: two EHEIM pumps at the same wattage despite one moving twice the air of the other.
Sized by the maker to a 40-US-gallon tank.
See the record →Sized by the maker to its own airflow, not a tank size: 200 litres of air an hour.
Half the rated airflow of the row above, for the identical wattage — the two figures come off two separate product pages in the same maker’s line-up.
Official specverified 2026-08-09aquarium air pump record · US + EU
What actually decides it
Three appliances, three different answers, and the pattern is where the number actually comes from rather than what the appliance is for. A kettle’s wattage is bounded by the wall it plugs into — a fact about the market and the circuit, not the water — so the same appliance built for two mains standards is rated two different ways. An oxygen concentrator’s wattage is bounded by the compressor’s own fixed job, which barely notices which wall it is plugged into. An aquarium heater’s wattage is bounded by neither: it is set by how much heat the tank on the other end of the cord loses, a property of the tank and the room, which is why the identical rating serves the identical size tank on both sides of the Atlantic.
None of this is guessable from the category alone. “Kitchen appliance,” “medical device” and “aquarium equipment” say nothing about which of the three patterns a specific model follows — only the manufacturer’s own two market-specific ratings, read side by side, say that.