Quick answer
The Ofenwerk K1 costs about 16p an hour in typical use and about 32p an hour at full power, at the Ofgem price cap of 26.32p per kWh (1 October to 31 December 2026).
K1 running cost calculator
How many hours a day?
How cold is the room?
An hour
16p
A day
63p
A week
£4.42
A month
£18.95
A 5-month winter
£94.75
Tip: your unit rate is on your energy bill or app, in pence per kWh. "Average room" assumes the heater is at full power 50% of the time once warm.
The maths, in plain English
The K1 uses 1200W, which is 1.2 kWh for every hour at full power. Multiply that by your unit rate: 1.2 × 26.32p = about 32p an hour.
But it won't run flat out all evening. Once the room is warm the thermostat switches it off, then back on as the room cools. In a typical room that's roughly half the time, so the average is about 16p an hour.
What it costs to run (current UK prices)
At the Ofgem price cap of 26.32p per kWh (1 October to 31 December 2026), a 1200W heater like the K1 costs about 32p an hour at full power. Once the room is warm the thermostat switches the heater on and off, so in normal use it averages about 16p an hour.
| How long | Typical cost per day | Over 30 days |
|---|---|---|
| 1 hour | 16p | £4.74 |
| An evening (4 hours) | 63p | £18.95 |
| A working day (8 hours) | £1.26 | £37.90 |
Your own price may be a little higher or lower depending on your region and tariff. See how we calculate running costs or try the running cost calculator with your own unit rate.
Cost per hour by heater wattage
Use this to compare any heater at today's UK price cap (26.32p per kWh).
| Heater power | Full power, per hour | Typical thermostat use |
|---|---|---|
| 500W | 13.2p | 6.6p |
| 1000W | 26.3p | 13.2p |
| 1200W (Ofenwerk K1) | 31.6p | 15.8p |
| 1500W | 39.5p | 19.7p |
| 2000W | 52.6p | 26.3p |
| 3000W | 79p | 39.5p |
What the K1 costs where you live
Ofgem sets a different cap for each region. Between the cheapest and dearest regions the difference is small:
- East Midlands (25.36p per kWh): about 30.4p an hour at full power, 15.2p typical
- UK average (26.32p per kWh): about 31.6p at full power, 15.8p typical
- Merseyside and North Wales (27.86p per kWh): about 33.4p at full power, 16.7p typical
On a fixed tariff, use the unit rate on your bill in the calculator above.
Plug-in heater vs gas central heating
At today's price cap, gas costs about 7.97p per kWh and electricity 26.32p, so a unit of heat from electricity costs about three times more.
That means gas central heating is usually cheaper for heating the whole house. A plug-in heater makes sense when you'd otherwise heat every room just to sit in one. Many households keep the central heating on a lower setting and use a heater to top up the room they're in. See plug-in heater vs central heating for more.
6 free ways to cut heating costs
- Close the door of the room you're heating.
- Draw the curtains as soon as it gets dark.
- Put a draught excluder at the bottom of doors.
- Turn off radiators in rooms you don't use.
- Use the heater's thermostat rather than full power.
- Wear a warm layer and keep a blanket on the sofa.
Help with energy bills
- Warm Home Discount: a yearly discount on electricity bills for eligible households.
- Winter Fuel Payment: for people of State Pension age who meet the rules.
- Cold Weather Payment: for some people on certain benefits during very cold spells.
- Priority Services Register: free extra support from your energy supplier.
Check current eligibility on GOV.UK or with your energy supplier.
The truth about "1p an hour" heaters
Some adverts claim a heater costs pennies a day or cuts bills by huge amounts. Every electric heater turns about 100% of its electricity into heat, so the cost depends only on watts, hours and your unit rate. To cost 1p an hour at today's price, a heater would have to use under 40W, nowhere near enough to warm a room. We publish our full method so you can check every figure.
Frequently asked questions
How much does a 1200W heater cost per hour in the UK?
At the Ofgem price cap of 26.32p per kWh (1 October to 31 December 2026), about 32p an hour at full power. With a thermostat, typical use is about 16p an hour.
How much does the Ofenwerk K1 cost to run?
About 16p an hour in typical use, or about 63p for a 4-hour evening.
How much does it cost to run a heater for a month?
Using the K1 for 4 hours a day in typical thermostat use costs about £18.95 over 30 days at today's price cap.
Is it cheaper to run a plug-in heater or central heating?
For one room for a few hours, a plug-in heater is often cheaper because you're not heating the whole house. For several rooms, gas central heating is usually cheaper, as gas costs about a third as much per unit.
Does a heater on a low setting use less electricity?
A thermostat setting uses less over time because the heater switches off once the room is warm. At full power, the heater uses its full wattage while it's on.
How do I find my electricity unit rate?
It's on your energy bill or app, shown in pence per kWh. If you're on a standard variable tariff, it's close to the Ofgem price cap for your region.
Can a heater really cost 1p an hour?
Not one that warms a room. To cost 1p an hour at today's price, a heater would have to use under 40W, less than an old light bulb.
Is the K1 cheaper to run than an oil-filled radiator?
Per hour at full power, yes: the K1 is 1200W and most oil radiators are 1.5–2.5kW. Oil radiators keep radiating after switching off, but they take much longer to warm a room.
Sources and how we checked this guide
- Electricity price: Ofgem: energy price cap unit rates and standing charges, checked 25 October 2026.
- Heater safety: UK fire and rescue service advice and Electrical Safety First guidance on portable heaters.
- K1 figures (1200W, about 2-second warm-up, room size up to 20 m², safety cut-offs) come from the product specification.
- Costs are worked out with the method on how we calculate running costs.
Compare: K1 vs oil-filled radiator · cheapest heater to run in the UK · energy-efficient heaters.