I’m manically going around the house and turning the lights off.
While saving any unnecessary energy use is a good thing, turning lights off, if they are LED’s, is small fry. The light fittings in our lounge takes 6 candle bulbs, the LED versions are 3.3W each, so it’s 20W for the whole fitting. Let’s say you turn the light on at 6pm then off at 10, you have used 0.08kWh - at the new price cap rate of 28p, that will cost you 2.24p. Do it every day for a year and it’s 29.2kWh, costing just over £8.
So yeah, don’t leave them on unnecessarily, BUT you will save a lot more by
a) making sure all your lights are LED, not compact fluorescent or (shudder) incandescent 100W bulbs
b) making sure your washing machine and dishwasher go on the eco cycles and are full when they go on (they use about 1kWh each per go - I can have the lounge light on for 48 hours solid for the energy used by one washing machine cycle)
c) using the oven less, or putting two things in at once; using a multi-level steamer to do potatoes and veg on one hob; using slow cooker and microwave rather than oven and hob. (A typical oven for 40 minutes plus hob for 20 minutes meal uses 1-1.5kWh. Put 2 ovens on at different temperatures and use 2 or 3 hot plates, you can double that - light on continuously for 4-5 days)
d) cutting down/out the tumble dryer, or replacing it with a heat pump version, which (apparently) uses about 1 kWh per cycle rather than 4.
In recent months I have learned a lot about energy use, motivated as much by environmental as financial concerns. So while I’m talking to the comfortably off: if you haven’t already done so, look into solar panels and home batteries, and/or changing your petrol/diesel car for electric. If you can spare the capital, these are both ways of reducing your future outgoings AND helping the environment.
Actually, if you normally lease or PCP your car, the fuel savings can be greater than the additional monthly payment, so that one is open to people without much capital.