Until I got solar, I just accepted what everyone had told me, I had no way to measure what way used by the immersion heater, and for years oil and gas per kWh was a lot cheaper to electric. We have always known using electric used less kWh, but the price resulted in gas and oil still winning.
But it costs to heat the boiler and pipework, and so a boiler always uses more power to electric. The problem is the break even point changes due to how much water used, and losses from the boiler, so in winter, the boiler is in use anyway, so heat up time for boiler does not matter, and also any heat escaping from the pipes, heats the house, the problem is how to ensure the domestic hot water (DHW) is heated only when boiler in use for central heating (CH)?
For me easy, using a C Plan so can't turn DHW off, so if boiler is running for CH then the DHW is also heated.
The Y and S plan not so easy. With
View attachment 423961View attachment 423962 a switch where the
X is a valve will open/close, but it will not fire boiler, so DHW only heated when CH is called. But it would require the switch being off so in winter DHW only heated when boiler is running anyway.
But, I have found, in winter not enough solar, and anyway solar paid at 12p/kWh and off peak cost 8.21p/kWh so for me, a simple time switch is enough and run the immersion heater overnight only.
But cost of electric varies even region to region never mind tariff to tariff, so although for me, no question an immersion is cheaper, not so sure if that would always be the case.
So we need a leap of faith, we simply can't work out the maths. Even with a combi boiler, with my mothers I had to have Eco on, as otherwise the shower would run cold, hot, cold then hot and stay hot, as the reservoir ran out before the boiler could heat replacement water. So taps had to be turned on full, set to a trickle and boiler would not fire, and needed even in the kitchen (where boiler located) to run a whole bowl of water to get hot water even to wash hands. Where here I would wash hands under the tap and only run half bowl of water, even after waiting for hot water to arrive. So likely use twice as much water with a combi boiler to with an immersion heater.
But, we are looking at electric price, since March mine has gone down, don't know when, did not realise until I looked at the app. The idea is to reduce energy use, I use smart socket adaptors, many tell me how much an appliance has used
View attachment 423963 this is the one used on the oil filled radiator, only used it yesterday, so the 1.7 kW is what I used to run the oil filled radiator last night. Cost is around 20p which is cheaper than firing up the central heating, this will change as we get more into winter, however we do need to check what things use.
I first did this some 10 or more years ago, in the main no surprises, most stuff has a label saying how much it uses, and the one watt limit has been in for stand-by for some time, the old Sky+ box was a surprise, as back then to be able to start recording early if there was a program change, it needed to keep the LNB powered so it could read the program guide, so was using more like 15 watts, so around £30 a year, the other three items, which are hard to work out costs, are the tumble drier, washing machine, and dishwasher, as there are so many programs, each one uses a different amount of energy, and they weigh clothes and vary amount of water heated etc, and sense humidity and change drying time. I found using a vented drier at 1 kW or a heat pump drier at 750 watts, worked out nearly the same. But with a condenser drier, often no option to turn down heat and extend the time, so they use a lot more power.
The other is the freezers, it may say 250 kWh per year, but most take more than the label says, so if it says 250 kWh per year, likely more like 350 kWh per year, however if they loose gas, they use more power, so every year I put the monitor on them, and see how it compares with the last year. Mainly as a warning it is likely to fail, rather than a reason to get new.
So we are left with the likes of the oven, can't use a plug in energy monitor, so we again have to guess, the smart meter or solar app may help, but you are measuring totals, so we look are different ways to cook food.
Deep fat frier, air frier, micro wave, fan oven, pan, kettle, and again gas v electric, if you can have a gas cooker. And resistive v induction as well.
So pick a food, for example a baked potato, the micro wave runs all the time it is cooking, but the air frier and fan oven, have thermostatic control, if the fan oven is needed to cook a pizza as well, then likely fan oven wins, other wise likely air frier wins, we tend to use microwave to part cook the baked potato then finish it with the pizza, giving cooked all the way through and outer skin looks right. So cooking method also affects the taste a little, but cooking is likely the most costly use of electric, having a afternoon dinner would cost less to an evening meal, as we would have solar, and it would be unlikely to cause battery to run out, but we like having an evening meal.
I was rather surprised when daughter compared boiling water in a pan on a gas cooker to using an electric kettle, in spite of the gas ring being rated 5 kW and the kettle 2.8 kW the kettle won by a massive margin, so repeated at home, induction hob and electric kettle, very little between the two kettle was best, but not worth transferring the boiling water, did not realise how much faster an induction hob is compared with gas.
So yes, if you don't have solar or battery, it may be worth looking at, but if doing it now, at 75 year old, I would need to live to 85 to save money, so that is not cut and dried.