Watt
A watt (W) is the unit of power, the rate at which an appliance uses energy while it runs. Watts equal amps multiplied by volts, so a watt figure tells you how much demand an item places on a supply.
Where you'll see it
Watts are printed on appliance labels, in manuals and on product pages for portable power. Campsites may state their supply in watts or amps. A watt figure describes demand while the item runs. It does not tell you how long a battery will last, which also depends on the battery's capacity.
What to check
- The power figure on the label or manual, and whether the maker lists it in watts or amps.
- Whether the label gives a separate figure for starting up, and which one the maker says to plan around.
- Whether the item is made for mains use, battery use or both, as the maker states.
- The site's stated limit, so you add up only the items you would run together.
Related terms
- Amp: the unit of current, which you multiply by volts to get watts.
- Watt-hour: a measure of energy, which depends on watts and how long they run.
- Load: the total power demand from everything you run at once.
Read more: Electric hook-up explained (UK) and the off-grid power needs calculator.