Panasonic "inverter" microwaves actually do reduce the power output. It's one of my favorite features. On power level 1 you can actually soften butter without melting random pits into it.

Unfortunately, at least on my current model, the UX to access this feature is very bad: repeatedly pressing the "power" button until it reaches the desired level. I've had other microwaves where you just key in the desired power after pressing "power", and much prefer that method.

I don't know whether Panasonic has licensed this to any other manufacturer.

Stir or otherwise rearrange what you're heating every so often, too. Microwaves deliver energy mostly to the outside of what they're bombarding, so it improves heat distribution to mechanically move the heated parts toward the center and vice versa - this helps prevent the "burnt outside and still cold in the middle" problem.

And on many microwaves, the “reheat” button is just a guided version of a low power mode.

The newer microwaves with a sensor reheat button are pretty great.

Some do operate in a "true" lower power mode (or at least in some mode that's indistinguishable to us). Ours does and it's great. But it's the first one I've had that actually does that; the rest have operated in lower power mode in the way you're describing.

Pretty crucial for defrosting. You really don't want to try to defrost a slab of lasagne say on 100%, 1kW or whatever, it's going to come out both just as frozen as when it went in and steaming hot ready to eat.

(I agree it applies just as well generally - but defrosting makes it more apparent/visible.)

> They don't actually reduce the 'power' of the microwave,

Depends on the microwave, you can get models that do adjust the power and they are very nice to use. Being able to slowly and evenly heat up food in the microwave is a huge game changer when it comes to how you use your microwave.