How much does it cost to run a 1 kw electric fire for 1 hour?

That’s a question many people ask and which we’ll explain below. With these steps, the cost of running any piece of electrical equipment can be worked out.

A. Quick answer:

Electricity cost calculator

Our Electricity Cost Calculator is designed to work out how much it costs to run individual electrical items. The important rating you need is the Wattage which is usually written on the item somewhere. Complete the yellow boxes, and the results are shown in the green boxes.

B. Detailed answer:

(Note: It’s easier to use the calculator to work this out.)

1. First, look for the power rating of the electrical item in watts or kilowatts.

In this case we are looking at a 1 kW electric fire

For information, note that 1 Kilowatt = 1000 Watts.

There is a wide difference between what different items cost. For example, a 60W light bulb uses very little electricity compared to a 1kW electric fire, which is the same as saying a 1000W electric fire. Heating costs a lot more than lighting. Imagine the power difference between a 60W light bulb and a 1000W electric fire and we’ll see how costs of each compare later.

Useful links: Low energy light bulbs; Halogen Fires

2. Calculate the length of time the item is being used.

In this case we are using 1 hour to work out the cost. Time is important. The longer you use it, the more power it uses, and the more it costs.

For some items you need to work out the time the item is actually on and using power. A fridge, for example, goes on and off as it works to keep the temperature constant. It’s only the “On” times that you need to know because that’s when it uses power. Best estimates may be required in lots of cases.

It’s important to recognise that the cost calculation below is based on the fire being continually “On” for the full hour. Electric fires with a thermostat which go “On” and “Off” as the reach they set temperature will be less expensive. It’s the “On” times that count.

3. Now we can calculate how much energy is used.

In fact, this is how electricity supply is measured: Power x Time used = Energy.

The electric fire is a good example. Let’s say we use the 1000 Watt fire for 1 hour. That’s the same as saying a 1 kilowatt (kW) fire for 1 hour. When you use the formula (Power x Time = Energy) you say 1 kW x 1 hour = 1 kilowatt Hour. And that’s how we get to the term Kilowatt Hour. It’s 1 kW x 1 hour = 1 kilowatt hour, or 1 kWh.

This bit is important and worth going over a few times to understand what a kWh is.

4. So, how do we calculate the energy used for the electric fire or a light bulb or any other electrical device?

What we have to do is work out the power rating and we have to do this in kilowatts. We know that the 1 kW fire is 1000 Watts equal to 1 kilowatt. So a 60 watt light bulb is 60 / 1000 = 0.06 kilowatt. And yes it’s very low compared to a 1 kilowatt electric fire.

• So the energy used by a 1 kilowatt fire in one hour is 1 kW x 1 Hr = 1 kilowatt hour.
• If we use the 1 kW fire for 2 hours, that’s 1 x 2 = 2 kWh’s.
• If it’s a 2 kW fire for 16 hours the formula is 2 x 16 = 32 kWh’s.

For a 60 watt light bulb, the costs are much lower because the lightbulb doesn’t use much power in comparison to an electric fire.

• A 60 watt light bulb  is only 0.06 kilowatts. (60 / 1000 = 0.06). So the energy used by a 60 Watt light bulb in one hour is .06 x 1 = 0.06 kilowatt hours. Hardly anything at all.
• If we use the 60 watt light bulb for 6 hours, that’s 60 / 1000 x 6 = 0.36 kwh’s.
• And 60 watts light bulb for 16 hours = 60 / 1000 x 16 = 0.96 kwh’s. Almost 1 kWh.

So the light bulb can run for 16 hours with the same power as used by a 1 kW electric fire.

5. Finally. how do we calculate the cost of the energy used?

Energy is sold in kilowatt hours (kWh’s) and the amount charged by suppliers is usually stated as Pence per kWh.

At this stage, have a look at your energy bill, o paper or online. Look for the cost per kWh. Don’t use the low rate (if there are two rates) but use the main rate, i.e. the normal rate which you pay after you have used up the cheap rate electricity. Bear in mind you may get discounts but this calculation is just to work out what the cost is before discounts.

Tariffs vary between suppliers and they also vary depending on what tariff name you are on, how you pay, and what type of meter you have. Government tries to make it simple to work out by standardising prices but in fact the easiest way is to use one of the free electricity price comparison services like the one we use on this site – see the calculator entry box below and try it out when you have a few minutes. It’s a happy calculator! Either it saves you money, or it reassures you you are already on a good deal!

So how does the energy cost calculation work? For the purposes of demonstration we will use a rough figure of 30 pence per kilowatt hour. (Actual standard tariffs will show on your bill). So for each kWh of electricity you use it will cost you 12 pence.

So, a 1 kW electric fire (= 1000 watts) running for 1 hour, uses 1 kWh of electricity (1 kW x 1 hr = 1 kWh). And 1 kWh of electricity costs about 30 pence (or the rate per your bill).

So how much does it cost to run a 1 kw electric fire for 3 hours?: A 1 kW electric fire running for 3 hours costs 1 x 3 x 30p = 90 pence.

The 60 watt light bulb running for 16 hours uses 0.96 kWh’s and that will cost just under 30 pence.

The actual calculation is as follows:

Power rating stated in kWh’s x The time in hours that it’s used = Energy used in kilowatt hours.
Then,
Energy used in kilowatt hours x cost per kilowatt hour = Cost in pence. Divide by 100 to get Cost in £’s.

So,

• A 1 kilowatt electric fire for 1 hour:- 1 kW x 1 hr = 1 kWh’s. x 30 p = 30p.
• A 2 kilowatt electric fire for 2 and a half hours:- 2 x 2.5 = 5 kWh’s. x 30 p = £1.50.
• A 3 kWh electric fire for 6 1/2 hours:- 3 x 6.5 = 19.5 kWh’s. x 30 p = £5.85

To work out how much the item costs in a month, multiply the hours per day by the days in the month as follows:

• A 2 kWh electric fire for 6 1/2 hours a day for 30 days at 30 pence per kWh is 2 kW x 6.5 hrs x 30 days x 30p / 100 = £117.
• A 60 watt light bulb for 14 hours a day for 30 days at 30 pence is 60W / 1000 to get to kW’s, x 14 hrs x 30 days x 30p / 100 = £7.56.

After this, you can use the same formula to work out the cost of any standard electrical item.

Things to bear in mind:

Many electrical items are more complicated because they may use regulated temperatures, thermostats, or variable power usages. You can use estimates for some of these but you need to be careful not to overstate or understate the power or time used. A thermostat will cut off the power when the set temperature is reached, so only when it’s “on” will it be using electricity.

The above is a rough guide which may be interesting but should be used carefully as no responsibility can be taken for the accuracy of the calculations. This is only for providing an idea of how the costs are calculated.

You can check and see if you can reduce your rate per kWh by using this free calculator.

Try it out now! Use estimated consumption if you don’t have exact details to hand.

(Costs update May 2022)

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