Taming the energy dragon – measure your energy consumption before you change suppliers

measure energy consumption

Faced with unprecedented hikes in energy charges, you may be looking around to switch suppliers to help cope with rising costs.

However, from my own research, I’ve learned that the biggest single contribution to energy savings doesn’t come from changing suppliers or tariffs. It comes from changing your usage patterns, finding out where you’re using most energy, and seeing where you can reduce those for rapid gains. It will probably be more than you save by changing suppliers. Don’t change suppliers until you have fine-tuned your usage patterns to gain the most economy first.

But you can’t change your usage patterns until you know what these patterns are, and which appliances use the most, and how often they are used. Measure your energy consumption first.

To do this for our household, I bought an inexpensive device for measuring electricity consumption in the home. The results were eye-opening.

What kind of electricity monitor do you need?

There are broadly two types of electricity monitor. There’s the kind that tells you the total electricity being consumed by the household at any one time, and though this information is useful, it’s not really suitable for checking how much your morning bagel costs to toast, it just displays an aggregate figure for everything.


The second type is intended for measuring the consumption of individual appliances, such as kettles, irons, washing machines and so on. They’re simple to use.  Simply plug it into a wall socket, plug the appliance into the monitor, and the monitor’s display will show how much electricity is being used from moment to moment, and in total. With most of them you can also enter the tariff, to see in real time how much your appliance is costing to use. For finding out usage patterns, you’ll get the most reliable information from this second type, and you can buy these relatively inexpensively, online or in a supermarket. They will pay for themselves very quickly indeed.

Measure energy consumption for different appliances

There are three broad classes of domestic appliance. First, those in use round the clock, such as fridges and freezers, which are usually on 24 hours a day. Second, those that run for a fixed cycle, such as washing machines, dishwashers, tumble dryers, toasters and the like. Third, those that are used for varying times, such as irons, vacuum cleaners, TV sets, and so on. To find out where the main energy costs are, simply measure the consumption of each appliance, either for a fixed period, or until it completes its cycle. This way, it’s easy to find out how much everything is costing per use or per ten minutes or per week.

For example, to measure how much electricity is consumed by a freezer, connect it to the monitor and let it run for 24 hours, and read off the total kWh at the end of that time, and then read the cost in pence.  That makes it easy to calculate the annual running cost, though as these appliances are on continuously, there’s usually little scope for economising. This is not where the big wins are.

For appliances like washing machines, which run uninterrupted until they finish, read the total usage from the monitor when the machine stops, so that you can see how much one washing cycle costs. It’s worth doing this for programmes that run at low temperature (eg 40°C) and higher temperatures (eg 60°C), because the difference is substantial.

For ‘ad hoc’ use appliances like a TV, vacuum cleaner, and so on, the principle is the same – connect it to the monitor, and read off the usage after, say, an hour, or maybe ten minutes worth of ironing or vacuuming. The key thing is to get a figure the cost of a normal use for a typical set time, and record it.

Calculating the cost of everyday energy use

I bought a notebook and pencil, set a page aside for each room, and made a list of all the appliances I wanted to test, room by room. Then for each appliance, I measured its consumption in average use, and recorded the results. That gave me a complete list of how much it took to use the toaster, boil a kettle, iron a pile of shirts, bake in the oven, wash and dry the laundry, and so on. It took a few days, but it wasn’t difficult. Then, with a calculator and the bill with the latest tariff, I pencilled the cost in pence against each entry. That gave me information about what every appliance cost each time I used it.

Are you on the best energy tariff?

The first result of doing this for our kitchen revealed that we were on the wrong tariff.  We had been sold Economy 7 by our supplier who persuaded us we’d save money by using the washing machine overnight and benefit from the lower night rates. The reality was different! Unexpectedly, the washing machine turned out to use relatively little electricity, and a large part of the cost of a washing load turned out to be in the detergent instead!

The tumble dryer was different. It guzzled electricity, taking over five times more to dry a load than it took to wash it. It’s not advisable to run a tumble dryer overnight unattended for fire safety reasons, so this meant that there were no off-peak savings for laundry at all.

Since nearly a third of our electricity usage would need to be in the off-peak period in order to break even (as Economy 7 day rates are higher than normal), we had been paying over the odds for years. The supplier made money, we lost. We don’t have storage heaters, which would have changed the picture, so cancelling Economy 7 saved us money straight away.

Alex’s results


Dishwashers usually have several programmes. Ours has a Normal, Economy and Quick setting. Measuring with the monitor showed that Normal and Economy modes used exactly the same amount of electricity! All that Eco mode saved was just two litres of water. The Quick programme by contrast takes half the electricity, but is not particularly effective on crockery that isn’t fairly clean already. The ‘Normal’ dishwasher cycle consumes almost as much electricity as the tumble dryer.


It’s heating that consumes electricity at the highest rate, so that’s where the quick gains are to be made. For instance, some ready meals can be cooked either in the oven or in a microwave. I cooked the same dish according to packet instructions, in three different appliances, an electric oven, a microwave oven, and an air fryer, to see which was the most economical. The cooking instructions called for minutes at 170°C in a conventional oven, or 4 minutes in a 700W microwave. I used the same setting for the air fryer as the oven.

The differences are striking. At around 30p per kWh, the conventional oven cooking cost was 14p, the air fryer cost 6p, and microwave cost just over 2p. Microwave savings are clearly dramatic, though if you like the browning of a conventional oven, or the skin crispness for baked potatoes that you can’t get in a normal microwave, air fryer is the next best choice for serious economy. I’ve now given up using the regular oven for all but things that need its greater capacity or size, such as when batch cooking for freezing in microwavable portions.


There are other areas for immediate money saving. For example, boiling up my kettle for a brew was often wasteful, as the kettle had a minimum volume, which often meant heating more water than was needed, and as it had no thermostat, it often wasted electricity when water didn’t need to be boiling anyway. It was costing around £70 a year to run. So I bought a smaller capacity kettle with a variable temperature control, and it heats exactly the quantity I need with no waste.  It cost £30 to buy, but over the same year, it has cost only £20 to run, so it’s already paid for itself.

Hot water

There is a view promoted by some that it’s more energy efficient to keep a tank of hot water continuously heated instead of letting it cool and then re-heating it. It’s not true. It’s more economic to use a timer to have the water ready for peak usage times, then have the timer turn the heating off.

Gas remains a cheaper fuel overall, even though it can be more wasteful of energy, simply because its cost per kWh is so much lower. It’s harder to measure the cost of heating something by gas, because of the way it’s supplied and metered, but I figured out a way to do that, and I was able to compare the cost of boiling a litre of water using three different appliances : on a gas hob, an induction hob, and a kettle. Induction hobs are known for being efficient compared to other electric hob types, so it was no surprise that the kettle and the induction hob used exactly the same amount of electricity, and it cost 4p to boil the litre. By gas, the cost was 2p, though it takes up to four times as long.


Some appliances consume almost as much electricity in standby mode as in use mode. For example, our Sky box was consuming 70% of the electricity it did when it was switched on. This isn’t true for all things with a standby mode, but unless you check it for yourself, you could be burning money. The Sky box alone was draining £26 a year just on standby.

Change habits, save money

Knowing what it costs to run things in our normal usage patterns makes it easy to change those to our advantage, and the changes in habits needed are not difficult, you just have to stick to them.  For example, switch from tumble drying to air drying where possible. If you like the tumble-dry fluffiness you get for towels that you don’t get from air drying, just air dry anyway and then pop them in the tumble dryer for fifteen minutes, when it’s going into its cooling cycle anyway, and that will do the trick.  Run fewer dishwasher cycles but with fuller loads. Use low temperature machine washes (30°/40°), as they only cost about a third that of high temperature washes (60° and over). It is also worth changing to low energy LED lighting, which can cost as little as £5 a year per bulb to run with average usage. Although it may not be a strategy for everyone, I replaced all our household lighting with LED smart bulbs, so I can now set automatic turn-off times for all lights in case any are inadvertently left running. But even just plain LED bulbs will save a small fortune.

The habit of change is easy to acquire, you just need to stick to it. To help it along, I made up small labels for each appliance, with the average cost of using it at different settings, as reminders. So, Dishwasher, 45p ; Washing Machine 11p low temp / 35p high temp ; Tumble Dryer 40p low / 60p high. And that morning toasted bagel? 1p. Knowledge is power!

To show how effective this strategy can be, by the end of the first year in which we changed our usage patterns rather than our supplier, our consumption had dropped so far below our direct debit budget that we had a refund from our supplier of just over £460. Not a bad return from an investment of £15 in an electricity monitor, a 90p notebook and pencil.


Image Credits:

  • louis-hansel-ktVKZRYUP4Y-unsplash: Photo by Louis Hansel on Unsplash


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