What Any Appliance Actually Costs You to Run

How the energy calculation works

Energy is power stretched across time. A watt is a rate. A watt-hour is what that rate costs you over an hour of use. Multiply average watts by hours used, and you have the day's energy. Multiply by the days in a week, then by fifty two, and you have a year. Divide by a thousand to move from watt-hours to kilowatt-hours, the unit your bill is actually priced in. Standby draw is handled the same way, except it counts every hour of the week, whether or not you touched the device.

The tariff step is just multiplication. Kilowatt-hours times the price you enter gives the cost, with no currency symbol attached, because that price already carries your own unit. A device costing thirty units a year is thirty units a year wherever you live. What changes between households is not the maths. It is the tariff, and the average draw you choose to believe about your own appliances.

• Average watts, not peak watts, decide the honest annual figure.
• Standby never stops counting, even on days you never switch the device on.
• Kilowatt-hours are just watt-hours divided by a thousand.

Worked example: a fridge versus a kettle

A modern fridge-freezer averages around eighty watts across the day, once its compressor duty cycle is folded in. Run that figure twenty four hours, seven days a week, and it draws about seven hundred watt-hours daily. Over a year that is roughly two hundred and nineteen kilowatt-hours. At a tariff of a quarter per unit, the fridge costs about fifty five units a year to run. It does that quietly and continuously, whether or not anyone opens the door.

Now take an electric kettle. Its label might say three thousand watts, which looks alarming next to the fridge. It boils for around four minutes a day. That is roughly two hundred watt-hours a day, or about seventy three kilowatt-hours a year. The kettle costs far less annually than the fridge, despite a label rating almost forty times higher. This is the difference between power and energy. A high rate over a very short time usually costs less than a modest rate that never stops.

Reading the appliance library

The reference table on this page collects typical average draws and rough annual energy figures for a spread of common appliances. Those numbers are planning ranges, not measurements of any specific model. Two fridges of the same nominal size can differ by half again in real yearly energy. Age, seal condition and the temperature of the room they stand in all move the figure. Treat the table as a starting point for a question, not the answer itself.

Use the table in one of two ways. Either find your appliance type, plug its typical figure into the calculator above, and adjust the hours to match your own habit. Or measure first with a plug-in energy meter. Use the table only to sense check whether your measurement looks ordinary, or unusually high for that class of device.

There is a second reason to read the table this way. It shows which habits, not which appliances, drive the biggest annual totals. A games console used three hours a day looks modest against a fridge that never stops. Change the hours, though, and the ranking can flip. The same device that seemed cheap to run becomes worth measuring once it runs all evening, every evening.

Where standby power actually goes

A single device idling at five watts feels trivial. Now add them up across one entertainment unit. A set-top box, a games console and a soundbar all left plugged in can draw a noticeable share of a year's electricity. None of that energy is doing anything anyone chose. Standby is easy to overlook because it has no sound, no light, and no clear moment of use. It arrives on the bill as a slow, constant line item you never consciously switched on.

The honest fix is usually a switchable power strip for one cluster of devices, rather than chasing individual plugs. That makes the standby decision one action at the end of an evening, not twenty small ones. A metered strip, or a plug-in energy monitor, will show you exactly how much of a device's yearly energy is standby rather than use. Sometimes the answer genuinely surprises the owner.

Accuracy, assumptions and limitations

This tool assumes the average draw you enter stays steady across the year. It also assumes your hours and days reflect a normal week, not a seasonal peak. Real usage drifts. A fridge works harder in a hot room in summer. A heater barely appears in the annual total for the months it sits in a cupboard. The calculator gives a single annual number built from the pattern you describe, which is a reasonable planning figure but not a meter reading.

For a dependable number, measure. A plug-in energy monitor costs little and logs real consumption over days or weeks. It captures duty cycling, standby behaviour, and the quirks of one specific appliance in one specific room. Use this tool to work out which devices are worth measuring first. That single question, answered honestly, usually finds the biggest savings faster than any general advice about turning lights off.