Heat pump against condenser tumble dryer, the real cost per load
A heat pump tumble dryer peaks at around 800 watts, which is 20.9p an hour at the Ofgem cap rate of 26.11p per kWh, but it only pulls that on the warm up. Across a full three hour cycle it uses about 1.5 kilowatt hours in total, so the honest figure is 39p a load or roughly 13p for each hour the drum turns.
Why the per hour figure misleads
Ask what a heat pump dryer costs per hour and you will be handed the plate rating, which for most nine kilo machines is around 800 watts. Multiply that by the cap rate and you get 20.9p an hour, so a three hour cycle apparently costs 63p and the whole efficiency argument collapses.
It does not work that way. A heat pump dryer runs its compressor hard while the drum and the heat exchanger come up to temperature, then settles into a cycling pattern where the compressor is off for a good part of every minute. The peak draw is real, it just is not sustained. Measure the whole cycle and a nine kilo cotton load comes in around 1.5 kilowatt hours, against the 2.4 you would get from three hours at 800 watts.
Bosch publishes a figure that settles it. The Series 6 WQG24509GB is rated at 258 kilowatt hours a year over the standard 160 cycle test, which is 1.61 kilowatt hours a cycle, with the full load cotton programme taking 176 minutes. That is close enough to the 1.5 kilowatt hours above to confirm the shape of it.
Work it out for your own heat pump tumble dryer
Type in the wattage from the plate on the back, then your own unit rate. The numbers update as you type.
What a load actually costs
Take 1.5 kilowatt hours as the working figure for a full cotton load. At the Ofgem cap rate of 26.11p per kilowatt hour that is 39p. Spread across a three hour cycle it averages 0.5 kilowatt hours an hour, or 13.1p for each hour the machine runs.
Smaller and drier loads come in lower. A half load, or a load that went in after a 1400 spin rather than a 1000, can finish nearer 1.0 kilowatt hour and 26p. A soaking load of towels can reach 2.0 kilowatt hours and 52p. The Bosch figure of 1.61 kilowatt hours sits neatly in the middle of that, and so does the 39p headline.
At three loads a week the month comes to 19.5 kilowatt hours and £5.09. Readers in the United States can run the same load against the EIA residential average of 18.34 cents per kilowatt hour, which puts a cycle at about 28 cents and a month at $3.58.
| Appliance | Typical draw | Usage we assume | Per hour (UK) | Per usage (UK) | Per month (UK) | Per hour (US) |
|---|---|---|---|---|---|---|
| Heat pump tumble dryer | 800 W | per 3 hour load | 20.9p | 39.2p | £5.09 | 14.7 cents |
Rates: Ofgem cap 1 July to 30 September 2026 at 26.11p per kWh (source), EIA residential average June 2026 at 18.34 cents per kWh (source). Checked 2026-09-22.
Against a condenser and a vented machine
A vented or condenser dryer heats fresh air with an element, pushes it through the clothes and throws the warm damp air away, either down a hose or into a tank. Every kilowatt hour of heat leaves the building. That machine pulls around 2.5 kilowatts while the element is on and uses about 2.5 kilowatt hours for a ninety minute load, which is 65.3p.
The heat pump does the same job with a refrigeration circuit. It takes the heat back out of the damp air before that air is thrown away, condenses the water off, and pushes the recovered heat straight back into the drum. The saving is 26.1p a load, or £40.72 a year at three loads a week.
Against that saving sits the purchase price, which is usually a couple of hundred pounds higher, and the time, which is roughly double. A heat pump pays for itself somewhere around year five or six on three loads a week, sooner if you dry more, later if you dry less. That is a genuine payback rather than a marketing one, and it is slow enough that replacing a working condenser early rarely makes sense.
Against drying indoors
The comparison that catches most people out is the heated airer, because it looks unbeatable on paper. A 300 watt airer running for four hours uses 1.2 kilowatt hours and costs 31.3p, which is 8p cheaper than the heat pump cycle. In a cold bedroom in November four hours rarely finishes the job, so the honest version is six to eight hours, 1.8 to 2.4 kilowatt hours, and 47p to 63p.
At that point the heat pump dryer is the cheaper machine as well as the faster one, and it has the advantage of putting the water down the drain rather than into the plaster of your bedroom wall.
Six ways to cut the cost of a heat pump cycle
- Spin at the highest speed your fabric allows. Every extra hundred revolutions takes water out mechanically at a fraction of the energy cost of taking it out with heat.
- Fill the drum to about three quarters. A half empty heat pump dryer still has to warm the drum and the heat exchanger, so the fixed cost is spread over fewer clothes.
- Clean the filters after every load and the heat exchanger filter every few months, because a restricted airflow makes the cycle run longer for the same result.
- Use the cupboard dry setting rather than extra dry for anything going straight into a drawer, which typically saves the last twenty minutes of the cycle.
- Keep the machine somewhere above about 10 degrees. A heat pump in an unheated garage in January is drawing heat from cold air and will take noticeably longer.
- Run it off peak if you are on a time of use tariff. A three hour cycle is long enough to sit entirely inside a cheap overnight window.
Is it worth buying one
For a household drying three or more loads a week through winter, yes. The £40 a year is real, the fabric comes out in better condition because the air is cooler, and the machine does not need a hose out of a window.
For a household that dries two loads a month, no. Buy the cheaper condenser and put the difference towards a better spin on the washing machine, since that is where the biggest energy saving in the whole laundry chain actually sits.
Common questions
How much does it cost to run a heat pump tumble dryer for 2 hours?
About 26p. A three hour cycle uses around 1.5 kilowatt hours in total, so two thirds of a cycle is close to 1.0 kilowatt hour, which is 26.1p at the current cap rate. Reading it as two hours at the 800 watt plate rating would give you 42p, and that is the mistake most calculators make.
Are heat pump tumble dryers cheaper to run than condensers?
Yes, by around 26p a load. A heat pump cycle uses about 1.5 kilowatt hours against 2.5 for a vented or condenser machine, which is 39p against 65p. At three loads a week that is £40 a year.
Do heat pump tumble dryers use a lot of electricity?
Less than any other way of tumble drying, because the machine recycles its own warm air instead of heating fresh air and blowing it out. Bosch publishes 258 kilowatt hours a year for its Series 6 nine kilo model over the 160 cycle standard, which works out at 1.61 kilowatt hours a cycle.
Why does my heat pump dryer take three hours?
Because it dries at a much lower air temperature, and low temperature drying is slow by design. Bosch lists 176 minutes for the standard cotton programme on a full load. The extra time is exactly what buys you the lower bill and the gentler treatment of the fabric.