I am sure like many others I assumed heating the DHW would cost a lot with electric, our tank has just the spray on ½ inch of foam they have come with for years, on fitting solar panels I also fitted a device which can use the spare solar, and it has a display
the result was realty a surprise, no where near the cost I had assumed was needed to heat my domestic hot water, only used in summer so can't show you a result today, but from memory a weeks DHW heating was around 3 kWh so around £1.
Off-peak even without any electric heating has halved my bills, as to if worth the hassle is another question. Setting the big three that the dish-washer, washing machine and tumble drier to run in the off-peak time does have a noise implication, in my large house not a problem, in a small flat it may be.
Knowing what you are using can help
this is my back-ground use, in the main fridge freezers, and freezers, I have 4 running, as live in the country, so food to last if snowed in, but also loads of ½ watts used by items in stand-by mode. It would be interesting to see how much smart lighting costs when lights are not in use, be it hubs for central heating control, or lights etc. Or the TV and set top box on stand-by, charging the phone, running a clock, I use something like this
to see what things use, the kettle is easy, written on it 2.8 kW but worst is the washing machine, even using the same program never seemed to get two load using the same amount of energy, in stand-by mode items are supposed to be limited to 1 watt, but I remember when I first went around checking, the Sky+ box at the time was drawing 15 watt.
If you look at a freezer it gives Annual Consumption example 200 - 299 kWh this is for a 200 - 299 litres freezer, as it ages it will use more, and the annual consumption is likely over what is stated, so lets for ease say 365 kWh is still not enough to be worth renewing, but 730 kWh is way over, so we measure a days usage, as it happens testing one of mine
OK my tester is connected to the PC, but it shows me 9.3 kWh for 26 days, so maths shows me 9.3/26x365 = 130 kWh per annum, so well within limits, the IHD (in home display) we get with a smart meter to me is useless, it swaps between
and
all day, as my solar and batteries take care of my daily load, but for those without solar and batteries I am sure it can help.
My off-peak would likely not suit you, it only runs for 5 hours, there are so many different tariffs, many location fixed, so no good me saying use this or that, as may well not exist in your area, with a single rate of 29.57p per kWh my standing charge was 62.21p per day, when I moved to 31.31p per kWh peak and 8.95p per kWh off-peak my standing charge dropped to 59.14p per day, I am sure done so hard to compare, in some cases the tariff has a name mine is called Electric Driver V5, but does not require me to have an EV, others you need to show you actually have an EV etc.
With an immersion heater it will need a timer of some sorts when you have an off-peak supply, this may be the electric supplier or the landlord, Economy 7 is the name of a tariff not a system, there are many ways to use it.
I have found Age Concern Wales, really helped me, not actually what I went to see them about, but loads of other little things, like my disabled badge, I did not want to admit I was disabled, Citizen Advice etc, may well come up with things you had not even thought about, it is easy to say "Report your landlord" but I know here many landlords have had enough and want to get out of letting homes, so often we do need the kid gloves approach, but there is a limit, and it needs some common sense applying.