How I (most likely) saved 10kWh a day at home

FaucetI noticed that my electricity account (paid by a monthly direct debit) was starting to accumulate credit over the course of the year, so I was rather happy when I got news that my monthly payment is to go down by just over £20 a month from April.

Of course, the monthly systems are prone to “swings and roundabouts”, where if your monthly payment is too high you end up with an account massively in credit and your electricity company sat on a load of your money, or the opposite, you’re paying too little each month and end up owing.

So, I did wonder if it had been reduced too much and I’d end up in arrears after a few months…

However, on closer investigation, my home is using less electricity each month compared to the same quarter last year, even accounting for our recent very cold winter. The bill has a graph comparing our average daily energy usage from the current statement against the same period the previous year.

It was around 10kWh a day less this year compared to last!

I wondered how we’d achieved this.

We hadn’t really changed any major appliances, we hadn’t cooked less, been away for weeks, or anything that would produce such a signficant change.

Then it dawned on me that our old immersion heater in the hot water tank (sadly, no gas at home, just electric) failed early last year, and was replaced with a new one. One of the reasons the old one failed was because it had become coated in limescale – London’s water is famously hard and nasty to anything with a heating element. Eventually, the build up causes the element to overheat, and eventually it can split (blowing the fuse, or popping the breaker).

The previously installed heater gave us very hot water. Steaming hot, and needing to be diluted with lots of cold water to be useable. You could hear the sound of boiling coming from the tank when the element was active, and the system was prone to airlocks – partly because of the water being overheated, and partly due to an error in the positioning of the expansion pipe when the property was built.

So, when the heater was replaced, I decided to turn down the thermostat from it’s default setting. Believe it or not, they are usuallyglued to around 65-75 C, with a little blob of silicon sealant. So, I popped the silicon blob off, and turned the stat down to about 55-60 C.

We still get hot enough water, and the only time it’s an issue is having a bath instead of a shower (the shower has it’s own water heater). A bath tends to run all the hot water off, or needs use of the “top-up” heater.

That’s all I can put such a significant and sustained change down to, but it’s looks to save about £20 a month. Talk about money down the drain!

Oh, and the system airlocks less frequently.

3 thoughts on “How I (most likely) saved 10kWh a day at home”

  1. Interesting. The bath temperature isn’t an issue so much, but I like to keep my water at a higher temp for washing dishes. Is that a concern or am I just a paranoid American who is scared of germs from a not completely clean hand-washed plate.

  2. I just realised. We did get a new washing machine. A more than 10 year old Whirlpool gave up the ghost earlier this year, and was replaced with a shiny new Miele.

    But even if I assume that the new Miele machine is responsible for 50% of the £20/month, then the machine stands to more than pay for itself in saved energy over it’s lifetime.

  3. Hi Mike,
    keeping the temperature of the tank down to ‘just too hot to stick your hand in’ is good chemistry. Limescale is deposited when the local temperature gets above 80 C. I set mine to 50 C. Quite hot enough for washing up, hotter won’t be that much hotter since you have to put your hands in to get the dishes out!

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