The cheapest energy savings are always the boring ones

Stack fabric first

Heat you never lose does not need a heat pump or a solar panel. Loft insulation, cavity fill and draught-proofing frequently clear payback hurdles that batteries miss — when the starting fabric is poor.

Apply measures multiplicatively in the insulation payback tool: you cannot save the same kilowatt-hour twice.

Then measure appliances

A plug meter plus the appliance running cost calculator will often find a dryer, old fridge or always-on PC that dwarfs LED bulb savings.