Microwave: Is 800 watts enough?

April 11, 2006 9:17 AM

Microwave oven: Is 800 watts enough?

I'm looking to buy a cheap microwave oven for cooking porridge, popcorn and reheating leftovers.

Most microwave ovens have a maximum effect of at least 900 watts but the really cheap ones I have been looking at only have a maximum effect of 800 watts. Is 800 watts enough or should I spring for one of the more expensive 900 watt microwaves?

posted by sveskemus to home & garden (21 answers total)

They'll take longer to heat things up. That's the only difference... if you can live with that, get a cheaper one.
posted by lemur at 9:23 AM on April 11, 2006

Thanks for your comment, lemur, although I was hoping for something a bit more specific.

How much longer would it take to cook, say, a bowl of porridge? Should I simply add the percentage difference between 800 and 900 or is it more complicated than that?
posted by sveskemus at 9:34 AM on April 11, 2006

800 watts should be more than enough. It's common for microwaves to be under this in Europe, if not in America. My parents had a 650W for years and we have a 700W here and it's perfect. I go for just under two minutes to do a bowl of porridge.

Furthermore, most ready meals here seem to have the instructions for 650W and 750W microwaves primarily, so.. if we can live with them, I'm sure you can :)
posted by wackybrit at 9:39 AM on April 11, 2006

Ah, I just noticed you're in Denmark. I apologize for the America references! Re-read my post with "the UK" instead of "Europe" then.
posted by wackybrit at 9:40 AM on April 11, 2006

The time difference between 800 and 900 watt is next to nothing. I have a 900w and in the UK at least, packaging guidelines don't even go up that far, most stop at 800w maximum then tell you to refer to your microwave instructions. I would say there is no need to splash out on a 900w microwave.
posted by fire&wings at 9:42 AM on April 11, 2006

There is no direct correlation between cooking times and whatever wattage the manufacturer assigns it. At best you might be able to make a relative assumption within a brand of fairly linear proportions, although we all remember radiated/resistive power has a geometric falloff, RIGHT? :)

What is the price difference, $20? I'd bet that for the lifespan of 5+ years you'll have it, you can probably afford it. The more powerful one may well be better made since it's not bottom of the line, anyway, with additional features you don't know about yet. Plus it gives you more options should you need the power. I'd think the more power you have available, the less chance your food will be cooked unevenly due to not having to nuke the fast-cooking parts as long to get the slower parts.
posted by kcm at 9:43 AM on April 11, 2006

although we all remember radiated/resistive power has a geometric falloff, RIGHT?

this is bullshit. the radiation in a microwave is a set of standing waves. there's no "geometric falloff" at all (and i have no idea what "resistive power" is referring to).

800 W will be just fine. the 900 W model is there for people like kcm who like to spend money rather than think.
posted by andrew cooke at 10:01 AM on April 11, 2006

Here in the U.S., most people I know have long abandoned their old 650W microwaves for 1000+W models. I have a 1100W that I bought for $80 3 years ago. It's like going from dial-up to broadband.
posted by tom_g at 10:06 AM on April 11, 2006

If you've never made much use of a microwave oven before, you won't mind a 'slow' one -- to you, it will seem mighty quick. But if you're already accustomed to a higher-wattage model, you'll never be satisfied with anything less. I bough a medium-power microwave because I needed a small footprint. Eight years later, I still haven't gotten used to it. But I care more about how it looks, so I suffer the wait.
posted by wryly at 10:20 AM on April 11, 2006

If you don't know what you're talking about, don't call me out in an ad-hominem fashion. Microwave radiation does indeed fall off in a greater-than-linear fashion meaning that as food is farther from the source, the power received is less than linear wrt. distance. This means that for any food not touching the radiation source, effectively, a 900W microwave is less-than-to-much-less-than 9/8th as powerful as an 800W model (though at least as powerful). You are not likely to notice the effect of power density dropoff WITHIN such a small distance, sure, but it's measurable even so.

Besides, none of this probably takes into account the efficiency. I'd bet the power rating is more closely related to energy draw than effective radiated power - and if it is, again, the more expensive model may be more efficient. Hell, it could be the same power plant with more efficient guts around it if they're good at marketing and commoditizing parts.
posted by kcm at 10:28 AM on April 11, 2006

I don't know if you do microwave popcorn in Denmark, but over here in the U.S., I've noticed that lower power microwaves tend to start burning the popcorn before it's fully popped.
posted by madajb at 10:30 AM on April 11, 2006

Maybe the price points work out differently in Denmark, so take this with a grain of salt.

In the US anyway, you can get a fancy microwave with all sorts of automatic functions and detectors and whatnot, with lots of power, and that's as big as you'll ever need for $120--$150. Or you could get a wee tiny one with no turntable, low power, and few features for $50.

In that case, I'd go with the bigger, better one. Small ones with few features are annoying in the long run. Microwaves last damn near forever, so it's more frugal in the long run to get one microwave for $120 than to spend $170 on two microwaves over five years.
posted by ROU_Xenophobe at 11:16 AM on April 11, 2006

Honestly, the slower cooking is better, IMO, because it gives the heat time to spread and the food is more evenly heated. I tend to run my microwave at half power all the time (5 out of 10).
posted by knave at 12:02 PM on April 11, 2006

What knave said. The only essential feature in a microwave is a turntable. Even the cheapest microwaves I've found in Toronto have that feature.
posted by lemur at 12:13 PM on April 11, 2006

I've been on the computer too long. I thought it said Microsoft oven. "They're doing appliances now?" *slaps forehead*
posted by vanoakenfold at 12:18 PM on April 11, 2006

The inverse square law only applies to stuff radiating in a three dimensional space. If you sandwitched a radiation source between two planar mirrors delivered power would be an inverse-linear relation to the distance instead of inverse square (it's dissipating along the perimeter of a circle (2πR) instead of a the surface of a sphere (4 πR² (sorry pi's look so awful in Verdana))

Obviously the sides of the microwave aren't theoretically ideal refelctors, but the fact that most of the microwave energy is bouncing around in there means that the distance from the emitter is less important.
posted by aubilenon at 12:28 PM on April 11, 2006

Manufacturers' measurement systems vary so wildly that 800w versus 900w is meaningless anyway. Brand A's 800w may actually be miore powerful than Brand B's 900.

Don't necessarily assume that bigger is better, either... I bought a large, 1200-watt microwave, and hated it. It was so powerful that it burned food on the outside before cooking it in the middle; I could rarely use it much past 70% power. I ended up switching to a smaller, less-powerful oven, and I'm very happy with it. (Sears' Kenmore brand, FWIW -- microwave/convection, $150ish)

Anything with 800-900 watts should be great. I suggest, however, not buying a bottom-of-the-barrel cheapie. A decently-built microwave can last you for many, many years. Don't get extravagant, but a solid midrange oven can save you money and hassle over the long-term.
posted by Malor at 12:40 PM on April 11, 2006

I find that microwave popcorn in an 800 watt microwave is difficult to manage. It's either burned or half the bag is popped. For Christmas I got an 1100 watt microwave, and the popcorn is crushed by the bag, leaving maybe one or two kernels unpopped, in under 2 minutes. It's crazy.

But aside from popcorn problems, I just cooked everything the maximum amount of time recommended on packages. I made popcorn in a 20 dollar air popper instead, which was healthier anyway.
posted by xyzzy at 2:55 PM on April 11, 2006

if you're worried about price, you may find waiting until mother's day will yield you a bargain microwave oven. In australia that's early may and for some reason they always have sales on household appliances on mother's day. I'm sure most mothers don't really want more appliances. I got my microwave, my food processor and my iron all really cheap on various mother's day sales. Do you guys even have mother's day sales though??

Back to the topic - we had a 650W for years and my new one was an 800W. Its got menu system in it where you can say "reheating - pizza - 4 slices" and it cooks it for you without you needing to know any details on what power needs what time. In addition when defrosting things (which is what I usually use my microwave for) you can opt for the super fast defrost (with the risk that the edges might get a bit cooked) or the careful defrost (which takes longer but the food is evenly thawed). This alone made it WAY better than the old 650w whereby you'd have to guess everything and cooking potatoes would take forever.

I think power rating is probably the LEAST important feature you should be looking at. Some kind of menu system which takes the guesswork out of it would be a lot more useful than an extra 100 watts.
posted by fossphur at 1:45 AM on April 12, 2006

also! there's a difference between inverter microwaves and non-inverter microwaves but I don't know what it is. I think inverters smoothly vary their power levels instead of just cutting in and out to get the power level right on average. were you looking at getting an inverter? I think an 800 watt inverter COULD be better than a 900 watt non interter. But i'm not sure.
posted by fossphur at 1:48 AM on April 12, 2006

Thank you all for your answers. I went out today and got a cheap (about $60) 800 watt microwave with a turntable. I'll try using it for a while and if I really hate it I'll sell it for $30 or something and get a more expensive one. I'll have lost $30 but at least I tried, right?

I've marked quite a few best answers. If you didn't get marked know that I appreciate your input anyway.

Once again, thanks for all your answers.
posted by sveskemus at 1:04 PM on April 12, 2006