when I pour cold water into the coffee maker, it only takes minutes before it comes out hot…how does it heat up so fast???
Very hot coils. The heating element in a coffee maker puts out an awful lot of heat for such a small amount of water, thereby heating it quickly.
How Stuff Works has pictures:
There are residential water heaters operating on a similer principle now. Instead of keeping 50 or so gallons of water hot at all times, water can be run through a short length of very hot tubing to provide hot water on demand. With these heaters, you’ll never run out of hot water, even if you run the shower all day long.
Well, never, that is, until you get your energy and water bills.
Get a screwdriver and see for yourself…
My coffee maker uses a pretty mundane metal heating element. The “trick”, is that it doesn’t try to heat all the water at once. It just heats the trickle going to the top, the flow being driven by the heating. The overall heat required to get the total volume of water to a certain temperature is the same either way, but the fact that it heats the water in small amounts allows it to produce a flow of very hot water for brewing almost immediately.
Schadenfreude: Do you happen to have any info about how hard a water heater like that would be to install, or if it’s possible to replace an old-style water heater with one of these newfangled ones? I’m curious, as our water heater really sucks and I’m tired of never having hot water.
MsWhatsit, do a search on tankless water heaters and I think you’ll find your answers. I checked out the site linked above and that site had some links to a couple companies. Controlled Energy and HeatStream are 2 such companies that sell tankless water heaters.
Thanks for the posting that link Schadenfreude, I am now considering one for my jacuzi which takes about 80 gallons. woohoo! 
I’ve seen ads for tankless water heaters–can anyone say if they’re any more efficient than the regular kind? they sound like they would be, but that’s not always the best way to judge, is it.
so do tankless water heaters really save money or energy?