Absolutly no idea. BUT - dh is a plumber, he has worked with them, says industrial ones are good but wouldn't put one in the house. Have started him off now, is shouting advice from afar! Apparently works on the same principal as boiler only with a fan in. NOt very common nowadays, he recommends electrical.

I have electrical tumble dryer - bloody marvellous and was about £140. If you don't have a vent / window condensing tds are very resunable nowadays.

Will update if dh comes up with any more words of wisdom!!!

Harrysmum, I dry stuff inside OK even in cool summer weather - if you get a tall rack (eg Minky,) and drape everything over 2 rails instead of one - IYSWIM - so the air gets inside them, they get dry enough overnight to just finish off in the dryer, or iron if you like ironing. My rack is next to an east-facing window. Big things like trousers and bedding hang over banisters. If it is a huge load and I run out of rails I do put socks and knicks straight in the dryer.

Can manage a load a day that way (5/6 of us here, 3/4 adult) - need to get a kind of rota going though. But it's better for the clothes not to be tumble-dried all the time if poss.

Gas dryers are pretty standard in the usa. Much cheaper to run than an electric one as electricity is much more expensive than gas. The clothes are dried just the same.... you can't tell the difference. The industrial ones tend to get too hot and "burn" the clothes, but the domestic ones are just fine.
Personally I couldn't live without a dryer. It also means that your clothes come out nice and soft (especially if you have a nice big american style dryer) and therefore you don't have to iron them. I do the the opposite of janh. I don't put my knickers in the dryer, so that the elastic isn't ruined by the heat. Otherwise everything goes in.

We looked at gas dryers but they were about £200 more expensive than electric ones to buy, add to that the installation costs and it takes an awful lot of loads to get your money back on the fuel savings. Remember that they still need electric to turn the drum so it is only the heat part of it that you are saving on. You can buy electric starting at £100.

Reverse tumble ones are supposed to crease the clothes less and the more energy efficient ones have a sensor that turns them off when the clothes are dry (I really miss that on mine now that it has stopped working - I just have to guess the length of time it needs now).

Go for a model with a better efficiency rating.

Sofia, I don't put MY knickers in the dryer, just everybody else's! (But as much because I can't afford to have them shrink even a millimetre as to save the elastic.)

And everything else gets tumbled for 10 minutes or so after air-drying and it finishes lovely and soft and smooth.

Seriously though I have some friends who rate a dishwasher above a tumble dryer but I'd rather wash up than have washing drying every where in the winter.

Don't get me wrong, I use my line whenever possible as I live under the remit that you shouldn't waste good wind