How to choose a microwave oven: watts, litres and the label that does not exist

Standing in front of a shelf of microwaves, the only number that jumps out is the wattage, and it looks like the simplest criterion in the world: more watts, more power. The trouble is that the number does not tell you how much the appliance draws, it does not last for the whole cooking time, and it cannot be compared against any label, because the microwave is the one kitchen appliance that has no energy label at all.

We at PortosEunostos read the technical data sheets of eight Bosch microwaves currently on sale, plus a whole retail catalogue of 149 models. The picture that comes out is not the one on the price tag: declared power and the power you pay for at the meter are two different things, the top level only lasts a few minutes, and price does not buy watts.

The short answer

To reheat, defrost and cook one plate at a time, 800 W of output power and a 20 litre cavity are enough, which is the cheapest configuration in the catalogue. Extra watts buy little, because above 600 W almost no appliance holds its power for the whole cooking time. Paying more makes sense for two reasons: the grill, if you want to brown food, and the volume, if you need to fit a serving dish. The rest is convenience.

The watts on the box are not the watts you pay for

The big number, 800 or 900 or 1,000 W, is the output power, the energy that reaches the food. What the appliance draws from the socket is a different field on the same data sheet, and it is always higher: across six Bosch models read on 2 November 2026 the gap runs from 36 to 201 per cent.

Two useful readings. The BFL7221B1 delivers 900 W while drawing 1,220, the BFL524MS0 delivers 800 while drawing 1,270: the more expensive model gives more and consumes less. And the jump from 1,220 to 2,050 W between the BFL7221B1 and the BEL7321B1, which share exactly the same cavity, is the 830 W of the grill, which is a heating element and not a wave.

The CEG732XB1 deserves a line of its own: its 3,010 W need a 16 amp circuit instead of the 10 amps of the others. That is the kind of wiring detail you discover once the electrician has already left.

Maximum power does not last the whole cooking time

This is the line almost nobody reads, and it sits in a footnote on all eight of the data sheets we downloaded, which in the original Italian reads «Tecnologia inverter intelligente: la potenza massima verrà impostata a 600 W durante gli utilizzi di lunga durata», that is, intelligent inverter technology sets maximum power to 600 W during long operations. In plain words: you get the 900 W for a short burst of reheating, then the appliance drops to 600 and stays there.

The manufacturer says the same thing in a more honest way elsewhere. On the product pages of the Series 8 models the five power levels are listed as «90, 180, 360, 600, boost». The fifth level has no number, it has a name. On the Series 4 and Series 6 models the same fifth level is written as 800 or 900 W. Same behaviour, two ways of telling it.

The practical consequence is simple: between an 800 W appliance and a 1,000 W one, over a few minutes of cooking the difference is far smaller than the price tag suggests, because both end up at 600.

How many litres you actually need

Cavity volume matters more than wattage, because it decides what fits inside. Twenty litres is a soup plate, twenty-five takes a serving dish, thirty-six is almost a small oven.

A note on method, because we redo the arithmetic. In three cases out of four the declared volume is the product of the three cavity dimensions rounded down: 230 x 350 x 270 mm makes 21.7 litres and the sheet says 21. In the fourth it is not: 201 x 308 x 282 mm makes 17.5 litres and the sheet declares 20. This is not an error, it is how you measure a cavity that is not a perfect box, but it does mean that twenty declared litres are not twenty litres of usable space. If you need to fit a specific container, look at the three dimensions.

Grill, hot air or nothing: here the price lies

On 2 November 2026 we read the entire microwave category of OpportunityCommerce: 149 models, median price 506.95 euro, from 138.00 for the cheapest to 2,349.00 for the dearest.

Read like that, the grill appears to save you two hundred euro, which is absurd. The explanation is that catalogue titles are not a classification, and the proof is in the Bosch sample: the CEG732XB1 is listed as a built-in microwave oven with no mention of a grill, and its own data sheet contradicts itself. Page 1 gives its additional functions as microwave only, page 2 calls it a microwave with grill and declares a 1.9 kW quartz grill. Anyone trusting the title buys without knowing what they are taking home.

The rule: check the function on the manufacturer's data sheet, never on the seller's title. And a true combination oven, the one with hot air, costs twice the median: if that is what you need, you are buying a compact oven, not a microwave.

Built-in or countertop: two different objects

The microwave everyone pictures, white and sitting on the worktop, is a minority of the furniture market: 8 models out of 149, median 205.57 euro. The rest are built-in, and 127 out of 149 are 60 cm wide.

If you go built-in, the first number to measure is the depth of the recess. The 38 cm tall models ask for 362 to 382 mm of height, 560 of width and 300 mm of depth: they fit in a wall unit. The CEG732XB1, 455 mm tall, asks for 450 x 560 x 550 mm, which means a full oven housing unit. It is the same logic as the recesses of built-in ovens: the size of the appliance and the size of the hole are two different figures, and the second one rules.

What one reheat costs

With no energy label there are no classes to compare, but the arithmetic still works using the power drawn. At the Italian ARERA tariff for the fourth quarter of 2026, 0.4343 euro per kWh, five minutes at full power cost 4.6 cents on a 1,270 W appliance and 10.9 cents on the 3,010 W CEG732XB1.

The comparison that really matters is with the oven. The EU data sheets of Bosch ovens declare 0.73 to 0.98 kWh per cycle in conventional mode, that is 32 to 43 cents: seven to nine times one microwave reheat. To warm up a portion, switching on the oven is the expensive choice.

PortosEunostos tips

• Measure the recess, not the appliance. Height, width and depth of the cabinet opening, before you even look at models.

• Check the power drawn, not just the output watts. Above 2,000 W make sure socket and circuit can take it; at 3,010 W you need 16 amps.

• Download the manufacturer's data sheet and read it to the end, footnotes included: that is where you find the grill the title never mentions and the drop to 600 W. Two of the Series 8 models we read declare no grill wattage anywhere.

• On the seller look at warranty, delivery times and return conditions before the price: on a built-in appliance a badly handled return costs more than the discount.

The Portos choice

For what most people actually do, reheating and defrosting, the right model is the 800 W, 20 litre one at the bottom of the catalogue, with a grill if the kitchen has no convenient oven. Going up to 36 litres and 1,000 W only makes sense if the microwave has to replace the oven on small portions.

What makes no sense is paying for power. In our sample the most expensive model without a grill costs 441.05 euro more than one with a grill, delivers 100 W more and offers one extra litre of cavity. Before you decide, compare prices and availability on SniffaPrezzi; if you already have a built-in model in mind, you can check features and availability on OpportunityCommerce.

Sources

• Bosch technical data sheets, downloaded on 2 November 2026: BFL7221B1 and CEG732XB1.

• Microwaves and combination microwave ovens on Bosch Italy: power levels and recess dimensions.

• Product list of the European Commission: domestic ovens and range hoods are there, microwave ovens are not.

• ARERA electricity tariff for the fourth quarter of 2026, 0.4343 euro per kWh (see what it costs to run your appliances).

• OpportunityCommerce microwave catalogue, 149 listings read on 2 November 2026.

If you are redoing the whole cooking area, read also how to choose a built-in oven, the figures on how much energy an oven uses and how to read the energy label, the one you will never find on a microwave.