Keep Above
Microwave or oven
Reheating and plenty of cooking can happen in a microwave or the oven, at very different wattages for very different lengths of time. Enter each one's rated watts, the minutes the job would take each way, and your own price per kWh — the page lands both on a cost per use, per week and per year. No winner is declared; every figure is yours.
On the rating plate or label
On the rating plate or label
Put in your price per kWh from your power bill, then each side's rated power and how long one use runs. Nothing here is read from your budgets, and nothing is saved.
| Option A | Option B | |
|---|---|---|
| Rated power | — | — |
| Energy one use takes | — | — |
| Cost of one use | — | — |
| Cost a week | — | — |
| Energy a year | — | — |
| Cost a month | — | — |
| Cost a year | — | — |
Does a microwave's power setting change what it costs?
At full power a microwave draws close to its rated input for the whole run, which is not how a thermostat-controlled appliance behaves. A lower setting is not a lower draw: the magnetron switches on and off in a repeating cycle, and the food coasts in the gaps. Ten minutes on a reduced setting is therefore not ten minutes at full draw, and entering it as though it were overstates that side.
The oven is the side where the plate figure and the real draw come apart, because a thermostat holds a set temperature by cutting the element in and out once the cavity is there. An oven also has to warm its own cavity, shelves and door before anything cooks, while a microwave puts its energy into the food from the first second. That warm-up is a fixed cost of the oven session rather than a rate, so a short job carries all of it and a long one spreads it.
This is one of the tools built into Keep Above
Keep Above is a budgeting app where you enter your bills and income and it works out the balance you need to keep — so you can see what's safe to spend. No bank connection, no ads on your data.
Running costs never arrive as a bill with a date on it; they show up inside the balance — budgeting apps with no bank connection sets out what each one asks you to keep entering.
About this calculator
Which wattage does a microwave's label state?
Microwaves usually carry two figures: the cooking power (what the food receives) and the rated input power (what the wall supplies), which is higher. The one that belongs here is the input power from the rating plate — the electricity being paid for — not the cooking power on the front of the door.
What about a grill or convection setting?
Those settings heat with an element rather than with microwaves, so for that run the appliance behaves like a small oven: a warm-up first, then the element cutting in and out under a thermostat. A rating plate that gives a separate input figure for those modes is giving you the one that fits that kind of job. The mode the job would actually use is the mode whose watts belong in the rated-power field.
Does a microwave draw its full rating the whole time?
At full power, close to it — there is no temperature being held, so nothing cuts out until the timer does. The oven on the other side of this page behaves differently: once it reaches the setting, the thermostat cuts the element in and out, and the draw across the session sits under the plate figure. Both columns are costed at full rated power for every minute, which is the upper end of each rather than a meter reading.
Where is the input wattage written on a microwave?
On the rating plate, usually on the back panel or on the frame the door closes against — not on the front of the door, where the figure printed is the cooking power. A built-in oven carries its own plate on the door frame too, and a freestanding one often on the back. Both plates give watts (W) or kilowatts (kW, where 1 kW is 1 000 W) for the input, and the price per kWh is read off your own bill.
Why is the number of uses shared between the two?
Because a use here is one meal heated, and the meal is the same errand either way. If the two sides could differ on how often, the page would be pricing two different weeks and the comparison would stop meaning anything. The length of a session is the part that honestly differs, and it sits in each side's own minutes field.