What you need to know
- Input power can be higher than cooking output.
- Short operating time often keeps total kWh modest.
- Compare appliances using the same cooking task, not just their rated watts.
Use your own measurements
Use the linked BricoDato resource to check these inputs in your own situation. A microwave advertised as '800 W' may mean 800 W of cooking output, not 800 W drawn from the socket.
Input power vs cooking power
A microwave sold as “800 W” may draw more than 1,000 W from the socket. Look for input power on the rating label or technical data.
Calculate from real minutes
Convert minutes to hours and multiply by kW. Ten minutes per day is only one-sixth of an hour, so time has a large effect on monthly energy use.
When it can beat an oven
For reheating or small portions, avoiding oven preheat and long cooking times can reduce energy use.
Measure combined modes separately
Grill or convection combination modes can change the electrical load and should not be treated as microwave-only use.
A microwave's input power changes the estimate
A microwave advertised as '800 W' may mean 800 W of cooking output, not 800 W drawn from the socket. For a consumption calculation, use the input rating on the appliance label or a suitable plug-in energy meter.
Example to adapt
If the microwave draws an illustrative 1,250 W while heating and is used for 12 minutes a day, daily energy is 1.25 × 12/60 = 0.25 kWh. Over 30 days that is 7.5 kWh, costing €1.50 at an assumed €0.20/kWh. A grill or combination setting may draw a different amount.
| Daily active heating | Energy at 1,250 W | 30-day energy |
|---|---|---|
| 5 min | 0.104 kWh | 3.13 kWh |
| 12 min | 0.25 kWh | 7.50 kWh |
| 20 min | 0.417 kWh | 12.50 kWh |
Checks before acting
- Find the appliance's electrical input wattage and distinguish it from microwave output.
- Record actual active-heating minutes over several days.
- Measure combination or grill modes separately, as the heating elements may change the load.
- Compare food quantities and cooking results when comparing microwave and oven use.
Final check
Distinguish cooking-output wattage from the microwave's actual electrical input. A programme labelled 700 W does not necessarily draw 700 W from the socket, and partial-power cooking may alternate on and off. To assess a common reheating routine, use a suitable energy meter for the full run and repeat with the same food mass and starting temperature.
- Use input power from the label.
- Add all daily minutes.
- Separate grill / convection use.
- Compare the same food quantity when testing alternatives.
Keep a small job sheet
Record input watts, daily minutes, operating mode and number of days.
Turn the guide into a decision
Record real kWh per completed reheating, portions and times per week. Compare an oven only if the desired result is equivalent; the microwave cannot deliver every browned or crisp finish, so a lower energy figure is not the whole purchase decision.