Start with energy, not wattage
A low-power device left on for many hours can use more energy than a high-power device used briefly. Multiply power by time before deciding what matters.
Measure variable loads
Fridges, heat pumps, dehumidifiers, computers and thermostatic heaters do not always draw one fixed power. A meter that records kWh over a day or week can reveal actual use.
Separate comfort from waste
For heating and cooling, building fabric, set-points and occupied hours can matter as much as appliance efficiency. Changes should still keep your home safe and comfortable.
Test one change at a time
Record a baseline, change one behaviour or setting, then compare kWh over a similar period. That makes the result easier to interpret than changing several things at once.
Price the result with your own tariff
Once you know the kWh difference, multiply it by your own energy price. If your tariff varies by time, savings may depend on when the electricity is avoided as well as how much.