THIS Simple Trick SAVES 80% on your Hot Water Bill!

THIS Simple Trick SAVES 80% on your Hot Water Bill!

Can an ELECTRIC hot water heater be CHEAPER than a GAS BOILER?

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I was pretty shocked when I saw how much energy prices are going up here in the UK now that we’ve “taken back control”, so I — like many others — wanted to see if there was anything that I could do, that I wasn’t already doing, to lower my energy bills going forward and hopefully reduce my carbon footprint, too.

So, on dull days when our solar thermal panels don’t give us hot water for free, I’ve stopped using our gas boiler to heat up our water tank and started using the electric immersion heater instead. This is better because firstly, my house is burning less fossil fuel and instead using the green electricity from my supplier and secondly with the geopolitical state of the world at the moment, I want to get my gas usage to as close to zero as possible.

“But hang on a minute!”, you might be saying, “everyone knows that using an electric immersion heater to heat up your hot water is far more expensive than heating it up with a gas boiler!”

Well yes, that has been the traditional school of thought for as long as I can remember but with the current energy prices, let’s have a quick look at the numbers to see if that still holds true. I’ll be showing you with my current prices so if you want to follow along, simply substitute in your own figures.

We have an 18kW system boiler at home (which will hopefully be replaced with a heat pump soon) but it won’t be running at full power all the time so we can’t just assume it uses 18kWh of energy per hour, it’s a bit more nuanced than that. So to measure how much it costs per hour to heat my hot water with gas, I took a precise meter reading and then started a 1 hour hot water boost from the Nest app on my phone before taking another afterwards.

Subtracting the starting value from the end value gives me the amount, in cubic metres, of gas used. You then multiply by your gas supplier’s calorific value (which you should be able to find on your gas bill), then multiply that by the correction factor of 1.02264 and divide that by 3.6 to give me a total figure of 8.59kWh of energy used.

My current gas prices are a whopping 7.36p per kWh at the moment so that gives a price of 63.22p per hour running the gas boiler to heat my hot water.

My electricity costs 25.87p per kWh so If I were to use the 3kW immersion heater for an hour instead, assuming it runs at full power for that hour, that would be 3 x 25.87 which equals 77.61p per hour which is more expensive than using the gas and also in my (fairly unscientific) tests seemed to increase the temperature of the water by only half that of the gas, too.

So, case closed?

HOWEVER! I’m on the Octopus Go electricity tariff which means my electricity price plummets all the way from 25.87p during the day to just 5p per kWh overnight — which is also when we charge our electric car once or twice a week, and we also schedule things like the dishwasher and washing machine to run during these hours too. By the way, this video isn’t sponsored by Octopus Energy, but if you’re interested in signing up for one of their intelligent tariffs with cheaper overnight electricity then I’ll leave my referral link in the description which means you and I both get a little bonus if you start the process using that link.

This hugely cheaper overnight rate means the sums for hot water look quite different — instead of 77.61p per hour to run the immersion heater it’s now just 15p per hour so even I run it for twice or even three times as long it’s still much cheaper than using the Gas boiler to heat our hot water and it’s better for the environment too because electricity is both cheaper and greener during off-peak times.

By my maths, the maximum cost to run a 3kW immersion heater for all 4 cheap hours at 5p per kWh would be 60p — cheaper than running the boiler for just 1 hour, and of course as the immersion heater is controlled by its own thermostat, it won’t necessarily even be on for the full 4 hours each night. I like to set the thermostat to let the water get as hot as possible, firstly so it’ll stay warm longer into the day and secondly so that when we use it for things like morning showers, we’ll be diluting the hot water with more cold meaning more cheaply-generated hot water will stay in the tank for longer. But do be careful not to scald yourself first thing in the morning!

Now I’m not expecting anyone to be setting multiple alarms to turn on and off an immersion heater during the night! To make sure it turns on at half past midnight and is off again by 4.30am, when prices shoot back up, I bought a smart WiFi controlled switch ( affiliate link) to replace the basic on/off switch on my landing. This is great because as well as being able to operate it manually if I need extra hot water during the day, it’ll connect to the rest of my Google Home ecosystem and then I’ve created a Routine in the app to turn it on at 00:30 and another to turn it off at 04:30.

If you’d like one of these switches for your home, I’ll leave a link in the video description where you can buy one for yourself. It must be a switch that’s specifically capable of switching the higher load that an immersion heater requires, so if you’re in any doubt or you’re not confident fitting it yourself then do get a qualified electrician to install it for you.

So I hope this video saves you lots of money! Let me know in the comments if it does, and thanks for watching!

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Originally published at https://www.switchedonnetwork.com on September 13, 2022.