Heat Recovery
Who makes a flue heat recovery device for residential use? hot water heater?

Simple enough-my hot water heater (gas) blows a huge amount of heat outta the flue. Why doesnt someone make a coil or something to run your incoming cold water into before it goes into the hot water heater to preheat the water?

Baxi Multi-Fit GasSaver GS1 (and others)

http://www.energysavingtrust.org.uk/Energy-Saving-Trust-Recommended-products/Heating/Passive-Flue-Gas-Heat-Recovery-Devices-and-Systems

www.ravenheat.co.uk

www.energycatcher.co.uk

I just read more about these things.
Not sure they are "retro fit" you might have to fit a new boiler / water heater.
Something to keep in mind when you do need to replace yours.