How to calculate the energy cost of an appliance

If you’re looking to shave money off your electricity bill, there are two key ways in which you may be able to do it. These are:

• Get a better energy deal so your energy costs less per unit
• Use less energy.

In practice, it’s generally a good idea to look into both of these avenues, as there could be significant savings to be made. Here, though, we’ll focus on one way you can make changes to use less energy. Keep reading to learn more.

Why calculate energy usage by appliance?

Everyone knows that reducing the amount of energy we use is important, not only for cutting down costs but also for helping the environment. But sometimes that advice can feel paralysing – exactly how can we use less energy? This is especially the case if you’ve already tried certain measures, such as turning off sockets when they’re not in use, switching off the lights when you leave the room and making sure not to overcharge devices.

Fortunately, there is an evidence-based way to identify changes that you could make to reduce energy consumption in the long term, and that’s to look at how much energy your appliances go through when in use. Even if you only use your washing machine, for example, when you’ve got a full load to save energy, the appliance still has to consume energy at some point in order to function. Calculating how much energy it uses allows you to compare different makes and models of a given appliance to see if there’s a better alternative for your bills. 

Luckily, this is a technique that anyone can use to help reduce their utility costs, whether you’re looking to save money on business electricity or domestic energy. In each case, calculating appliance energy usage can help you to save money on energy bills so you can spend it where it really matters, such as recruiting staff or treating your loved ones.

How to calculate appliance energy usage

Every appliance comes with information about how much energy it consumes in an hour – a figure measured in Watts (W). For example, you might have a 40W light bulb. Similarly, your electricity is sold to you at a given rate per unit, where a unit is one kilowatt-hour (1kWh). This is how much it will cost you to use 1,000W for a duration of an hour.

Therefore, in order to calculate how much an appliance costs to run, you need to know the price you pay for electricity per unit, the wattage of the appliance in question and how long you typically use it for over whatever period of time you want to use. For illustrative purposes, we’ll look at the cost per day, but you could also use this calculation to find out how much an appliance costs you per week, per month or per year. This may be more useful for appliances that you don’t use every day, as it gives you a more realistic view of what you can expect to pay on average.

So, let’s say you have a 500W fridge. The first step is to convert from watts into kilowatts – so divide the wattage by 1,000. 

500W / 1,000 = 0.5kW

Next, you need to think about how many hours you’d expect to use the appliance in the time period you’re calculating figures for. We would expect to have a fridge running for 24 hours in a day, so we need to multiply our kilowattage by 24 to get the amount of energy used in that time.

0.5kW x 24 = 12kWh

So, that means that our fridge uses 12 kilowatt-hours of electricity in a day. Now we need to know how much we pay per kWh and multiply that by the figure we just got. For this, we’ll use an example of 30 pence per kWh. 

12kWh x £0.30 = £3.60

Therefore, running our fridge for a day would cost roughly £3.60. If we were to switch to a lower wattage fridge, we could save money on our energy bills – but it’s always worth taking into account other factors when making decisions on which appliances to have. For example, another fridge might cost a bit more to run, but incorporate additional desirable features like a water dispenser or a touchscreen display. If that’s something you want, you need to take it into account. 

It’s also worth considering other aspects of energy efficiency. For example, let’s say there are two washing machines which have the same wattage, but one can finish a wash quicker than the other. Because it’s in use for a shorter period of time, it costs less to run overall than the machine that uses a longer cycle.

If you wanted to find out how much your fridge cost to run for a month, you could estimate this by multiplying your daily cost by 28 to get a rough idea. For items that aren’t used all the time, though, you’re better off calculating how many hours on average you use it for during a month and using that figure rather than how many hours in a day. This will give you a more accurate figure with which to calculate energy usage.