Immersion heater first, mine will turn on at the thermostat around once every 3 to 4 hours, it does not stay on for long, the spike is about the same as the electric kettle, once it had warmed up first time in the day, the Octopus app is useless as it only shows in ½ hour blocks, even the solar software old shows spikes

so can't work out except for first this which is immersion and which is kettle.
Also the water temperature used to be scalding hot and turning the thermostat down had no effect. So, thermostat not working.
It should be at least 60ºC to stop legionaries, which is scalding hot, if it does not switch off with the thermostat, then the cut-out should work, and these need a manual reset, if no cut-out it would boil the water, which you would hear. And the cold water tank would get warm.
268.83 kWh at 32.277p/kWh = £86.77 without the standing charge, around £108 with standing charge. That's less than we paid before fitting solar, so not unreasonable. About £31 more to your last home, so around £1 a day extra or 3 kWh, so last year my immersion heater

and this year

so I have used a lot more this year, and not a clue why, we do not use hot water fill on washers and driers, or even the shower, only used to wash our hands.
I have an array of plug in energy meters, two only measure, which is what I want for the freezer, don't want it to turn off, but the rest can also switch items on and off, the Tapo (TP-Link) P110
is a multi-function device, and I use it to turn lights, fans, air conditioning, and battery chargers on and off, it says "Hub Not Required" I have the hub, so don't know if that alters what it can do, but find them handy to ensure at least once a day things are turned off, as to if they pay for themselves hard to say, but to turn outside lights on with phone before leaving car, and off in the house with a voice command means well worth it for me. (I have Nest Mini for voice command bit)
The smart meter I find next to useless, even if no solar, to work out what is drawing power is hard, you can get clamp-on meters to measure all,


But £76 is a lot to pay, it needs the hub, and yes a good display on the computer

better than the smart meter, one shown is from the plug in monitor, there are cheap ones
not a clue how well they work? But working out what has produced the spikes is near impossible.
But I have moved my plug in energy monitors around, and measure a washing machine, and never the same results twice. It weighs the wash, and alters program to suit.
July 2025
July 2026 and yes my consumption has hardly altered, 2024 422.4 kWh not record any further back.