How Much Does It Cost to Run a Caravan Heater? The kWh Maths
A 1,500W caravan heater uses 1.5 kilowatt-hours for every hour it runs at full output. At a metered rate of 30p per kWh that is 45p an hour, or 1.80 pounds across a four-hour evening. Over a fortnight's touring that is around 25 pounds, and that is before you account for the heater running overnight or during the day.
Those are the headline figures. The useful part is knowing how to calculate it for your own heater, your own site rate and your own usage, because the rated wattage on the box is not what you actually pay for.
The calculation, in three steps
- Convert watts to kilowatts. Divide by 1,000. A 1,500W heater is 1.5 kW.
- Multiply by hours. 1.5 kW for 4 hours is 6 kWh.
- Multiply by your rate. 6 kWh at 30p is 1.80 pounds.
Use your site's actual metered rate rather than the example. Rates vary considerably between sites and between seasons, and some sites include electricity in the pitch fee, in which case the marginal cost of running the heater is nothing at all.
Cost by setting
| Setting | kWh per hour | Per hour at 30p | 4 hours | 8 hours | 7 nights at 4 hours |
|---|---|---|---|---|---|
| 500W | 0.5 | 15p | 60p | 1.20 pounds | 4.20 pounds |
| 750W | 0.75 | 23p | 90p | 1.80 pounds | 6.30 pounds |
| 1,000W | 1.0 | 30p | 1.20 pounds | 2.40 pounds | 8.40 pounds |
| 1,500W | 1.5 | 45p | 1.80 pounds | 3.60 pounds | 12.60 pounds |
The spread between the top and bottom row over a week is about 8 pounds. That is the entire argument for a heater with more than one setting.
Why the rated figure overstates what you pay
A heater with a thermostat does not draw its rated power continuously. It heats until the cabin reaches the set temperature, switches the element off, and switches it back on when the temperature drops. The proportion of time it spends actually drawing power is called the duty cycle.
In a reasonably insulated touring caravan on a mild evening, a thermostatic heater might run for perhaps a third of the time once the van is up to temperature. The same heater set to the same output in a cold, draughty van on a windy night might run continuously.
| Setting | Duty cycle | Actual average draw | 4 hours at 30p |
|---|---|---|---|
| 1,500W | 100%, van never reaches temperature | 1,500W | 1.80 pounds |
| 1,500W | 50% | 750W | 90p |
| 1,500W | 33% | 500W | 60p |
This is why a heater with an adjustable thermostat is cheaper to run than an identical heater without one, despite both converting electricity to heat with exactly the same efficiency. The Ceramic Heater MKK-230 has an adjustable thermostat and three heating levels at 500W, 1,000W and 1,500W, which is what makes the duty-cycle saving available to you.
All electric heaters are equally efficient
This is worth being clear about, because a great deal of marketing implies otherwise. Any resistive electric heater turns essentially 100% of the electricity it draws into heat in the room. A 1,500W ceramic heater, a 1,500W oil-filled radiator and a 1,500W halogen heater all produce the same amount of heat from the same amount of electricity.
What differs is how the heat is delivered and therefore how comfortable you feel for a given setting:
- Fan heaters warm the air quickly and move it around, so they feel effective fast and are good at reaching a set temperature and then cycling off.
- Oil-filled radiators warm slowly and hold heat, which suits continuous background use but takes a long time to make a cold van comfortable.
- Radiant and infrared heaters warm objects and people directly rather than the air, which is why they work in awnings and other spaces where you cannot realistically heat the air at all.
None of these is cheaper per kilowatt-hour. Choose on delivery, not on an efficiency claim.
What the heater costs relative to everything else
| Appliance | Typical session | Energy | Cost at 30p per kWh |
|---|---|---|---|
| Heater at 1,500W | 4 hours | 6 kWh | 1.80 pounds |
| Air fryer at 900W | 20 minutes | 0.3 kWh | 9p |
| Kettle at 1,000W | 3 minutes | 0.05 kWh | 1.5p |
| Toaster at 920W | 4 minutes | 0.06 kWh | 2p |
| Washing machine at 180W | 15 minutes | 0.045 kWh | 1.4p |
The heater is not one line on the bill among several. It is effectively the whole bill. Everything else is rounding.
Working out a whole trip
Per-hour figures are easy to dismiss. Trip totals are not, so it is worth doing the sum once for the way you actually tour.
| Trip | Heated hours | At 500W | At 750W | At 1,500W |
|---|---|---|---|---|
| Long weekend | 12 | 6 kWh, 1.80 pounds | 9 kWh, 2.70 pounds | 18 kWh, 5.40 pounds |
| One week | 35 | 17.5 kWh, 5.25 pounds | 26 kWh, 7.88 pounds | 52.5 kWh, 15.75 pounds |
| Two weeks | 70 | 35 kWh, 10.50 pounds | 52.5 kWh, 15.75 pounds | 105 kWh, 31.50 pounds |
| A winter season, 20 nights | 100 | 50 kWh, 15 pounds | 75 kWh, 22.50 pounds | 150 kWh, 45 pounds |
Across a season the difference between running on 500W and running on 1,500W is around 30 pounds at the example rate, which is more than the heater costs. That is the practical case for buying one with a thermostat and multiple settings rather than the cheapest single-element model.
Checking your figures against the meter
If your pitch has a meter, read it at the same time on two consecutive evenings and note the difference. That gives you the whole van's consumption including the charger, the fridge on mains and the water heater, not just the fan heater.
Most people find the total is higher than they expected, and that the extra is the fridge and the water heater rather than the fan heater. It is worth knowing which before you start economising on the wrong thing.
Five ways to lower the number
- Use the lowest setting that holds the temperature, and let the thermostat do the rest.
- Heat continuously and gently rather than in bursts from cold.
- Fit thermal blinds and close them at dusk. Windows lose more heat than any other surface.
- Heat the space you are occupying and close the doors on the rest.
- Deal with draughts. A draughty van never reaches its set temperature, so the thermostat never switches off and you pay the full rated figure all evening.