Which appliance should I look at first?

Whatever heats, cools or dries. Electric heating, tumble dryers, immersion heaters and electric showers dominate almost every bill. Lighting and electronics are rounding errors by comparison, despite getting most of the attention.

Is it cheaper to leave the heating on low all day?

Generally no. A house loses heat faster the warmer it is relative to outside, so keeping it warm all day loses more total heat than reheating it when needed. The exception is a very well-insulated home with a heat pump, where steady low-temperature operation can be more efficient.

Electricity Cost Calculator

Estimate monthly and yearly electricity costs.

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What an appliance actually costs to run

Running cost is wattage times hours times your unit rate. The arithmetic is trivial; what surprises people is which appliances dominate the bill, and it is almost never the ones they think.

How it works

Converts an appliance's power rating in watts to kilowatts, multiplies by hours of use, and multiplies by your price per kWh.
Scales the result to a day, a month and a year, since the annual figure is the one worth acting on.
Uses your own tariff rather than a national average, which can differ by a factor of two.

kWh    = (watts ÷ 1000) × hours
cost   = kWh × price per kWh
annual = daily cost × 365

heat is what costs: anything that heats or cools dominates
  kettle 3000 W    tumble dryer 2500 W    oven 2000 W
  fridge 100 W (but runs continuously)    LED bulb 9 W

Worked example

An electric heater rated 2000 W, used 5 hours a day through winter, at 0.28 per kWh.

2000 ÷ 1000 = 2 kW
2 × 5 = 10 kWh per day
10 × 0.28 = 2.80 per day
over a 120-day winter: 2.80 × 120 = 336

336 for one heater over one winter. By comparison, a 9 W LED bulb left on 5 hours daily for a whole year costs about 4.60 — the heater costs more in four days than the bulb does in a year.

Reading the result

Standby power is real but small. A collection of devices on standby might add 20–50 a year; a single electric shower or tumble dryer will beat that in weeks. Chase the heat, not the little red lights.
The wattage on the label is peak draw, not continuous. A fridge rated 100 W cycles on and off and may average 30 W; a kettle at 3000 W really does draw 3000 W, but only for three minutes.
Check whether your tariff has different day and night rates. Running a dishwasher or washing machine overnight on an economy tariff can halve its cost for no change in behaviour beyond a timer.
The unit rate here is what you actually pay including standing charges spread across usage, not the headline rate — those can differ noticeably on low-usage households.

Common questions

Which appliance should I look at first?: Whatever heats, cools or dries. Electric heating, tumble dryers, immersion heaters and electric showers dominate almost every bill. Lighting and electronics are rounding errors by comparison, despite getting most of the attention.
Is it cheaper to leave the heating on low all day?: Generally no. A house loses heat faster the warmer it is relative to outside, so keeping it warm all day loses more total heat than reheating it when needed. The exception is a very well-insulated home with a heat pump, where steady low-temperature operation can be more efficient.