How much does an immersion heater cost to run?
An immersion heater typically draws around 3000 W while running. Ratings vary widely between models, so check the label and change the figure below.
per kWh
W
g CO2 per kWh
Cost per year
615.45
- Cost per month
- 51.29
- Cost per day
- 1.69
- Cost per hour of use
- 0.84
- Energy per year
- 2198.0 kWh
- Energy per day
- 6.0220 kWh
- Carbon dioxide per year
- 549.5
- Annual cost of standby alone
- 2.25
Show the working
- Power = 3000
- Hours per day = 2
- Days per year in use = 365
- Electricity price = 0.28
- Standby power = 1
- Grid carbon intensity = 250
- kw = 3000 / 1000 = 3
- daily_kwh = 3 * 2 = 6
- standby_kwh = 1 / 1000 * (24 - 2) = 0.022
- Energy per day = 6 + 0.022 = 6.022
- Energy per year = 6.022 * 365 = 2198.03
- Cost per day = 6.022 * 0.28 = 1.686 16
- Cost per year = 2198.03 * 0.28 = 615.448
- Cost per month = 615.448 / 12 = 51.2874
- Cost per hour of use = 3 * 0.28 = 0.84
- Carbon dioxide per year = 2198.03 * 250 / 1000 = 549.508
- Annual cost of standby alone = 0.022 * 365 * 0.28 = 2.2484
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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Recent calculations
The formula
- daily energy = power in kW x hours
- annual cost = daily energy x days x price per kWh
Nameplate wattage is the maximum draw, not the average. A cycling appliance like a fridge or a freezer averages far less.
Standby draw is small per device and adds up across a house: ten devices at 2 W each is 175 kWh a year.
Running cost of an immersion heater at different tariffs
| Price per kWh | Per hour | Per year at 2 h/day |
|---|---|---|
| 0.10 | 0.3000 | 219.00 |
| 0.15 | 0.4500 | 328.50 |
| 0.20 | 0.6000 | 438.00 |
| 0.25 | 0.7500 | 547.50 |
| 0.30 | 0.9000 | 657.00 |
| 0.40 | 1.2000 | 876.00 |
Frequently asked
How many watts does an immersion heater use?
Typically around 3000 W while running, though models vary. Check the rating plate.
How much electricity does it use per day?
About 6.00 kWh at 2 hours of use.