How to Work out the Running Costs of Your Electric Heating

With the cost of living crisis dominating the new cycle and with energy bills getting higher and higher, you may be looking to alleviate the squeeze in your home. The Energy Saving Trust estimates that heating and hot water accounts for over half of your yearly energy bill, so it’s a great place to save some money.

In this article we’ll look at how to calculate your energy costs.

Understanding the limitations

Working out your energy costs isn’t as straight forward as it might initially seem. It can depend on a number of variables, including the size of your home, insulation quality, the efficiency of your appliances, the number of people in your home, and more!

The energy costs of things like a TV can be simple, as typically they will be on for a certain portion of the day, and off for the rest. But heating and other appliances with thermostats (like ovens or fridges) are likely to be in a constant state of turning on and off to maintain a certain temperature.

We can, however, use the formula below to work out a broad estimate.

1. Convert Watts to kWh

If your appliance’s energy usage is provided in Watts, you will need to convert it first to kilowatts. This is because energy costs are calculated using kilowatt hours (we’ll come back to the hours in a moment).

Converting to kilowatts is simple, as you just divide the Watts by 1000. For example, a super-efficient Devola 1000W Smart Glass Panel Heater divided by 1000 gives us 1kW. A 1800W heater would be 1.8kW, and a 450W heater would be 0.45kW.

Next, the hours.

To calculate this, you need to estimate how long the heater will be on for. Let’s say we’re using our 1kW heater in winter, so it’s running on full power for 6 hours a day. This would give you 1kW x 6 = 6kWh.

2. Input your own energy costs

In this step, you will need to find the cost that your energy provider is charging you. This should be listed somewhere on your bill.

If you are on the standard variable tariff, the cost* of your energy is fixed at £28.62 per kWh for electricity and £7.42 per kWh for gas thanks to the Government’s Energy Price Guarantee.

*These prices are as of 1 January to 31 March 2024.

We’ll use these figures for our calculations.

Our 1000W panel heater uses 6kWh to run. So we need 28.62p x 6kWh. This means that our heater costs 171.72p per day to run, or £1.72.

3. Multiply by the number of days

Now that we have our daily cost, it’s easy to work out a week, a month, and a year of running your appliance.

Simply multiply by 7, 30 (for an average month), or 365.

Say we use our heater every day for a month, it would cost £51.60 (£1.72 x 30 = £51.60).

4. Multiply by the number of devices

The above calculation provides the cost for running a single electric heater. To determine the total cost for heating your room, you'll need to multiply this figure by the number of heaters you're using. This will give you a more accurate understanding of the overall expense associated with keeping your space warm.

Account for realistic use

Now hang on. That number might seem dramatically high, but before you never switch your heating on again – remember what we said at the start.

Our figure of £51.60 is calculated assuming that our heater is on full power, 6 hours a day for 30 days straight. This simply isn’t how your appliance is likely to be used.

Heaters don’t run all the time, they switch on and off to maintain the heat in your room. Similarly, you don’t need them on for the whole month, as you’re at work, on a holiday, or others.

This is where our formula falls down, because it’s almost impossible to know when and how much your heater is actually running. This is why the figure generated should be considered a worst case scenario, and you don’t have to multiply it by a month like we did – as you know how many hours/days you use your heating for.