This is inspired by Bungston's integrated air conditioning and clothes-dryer idea. A refrigerator works by pumping heat out into the surroundings, which means that your kitchen gets a little bit warmer and your air conditioning has to work a little bit harder to move the heat from your refrigerator outdoors. Then the polar ice caps melt and we all die. So, why not take the hot tubing from the back of the refrigerator and wrap it around the hot water heater? Less work for your AC, and you get hot water much more efficiently because it takes less electricity to bring the water to full temperature.
-- DIYMatt, Jul 13 2011

Bungston's idea Integrate_20air_20c..._20dryer#1310519912
Integrated AC and clothes dryer [DIYMatt, Jul 13 2011]

Stirling Home System Stirling Home System
Another idea inspired by the lost heat around the back of the fridge. [zen_tom, Jul 13 2011]

Heat Pump Hot Water Heater http://www.energysa...x.cfm/mytopic=12840
Baked [goldbb, Jul 15 2011]

and when the water is hot how hard does the 'fridge have to work to cool off ?
-- FlyingToaster, Jul 13 2011


This is entirely baked. See hybrid water heaters.
-- RayfordSteele, Jul 13 2011


Hybrid water heaters are described as a compromise between tanked and tankless water heaters, but with no concept of using different energy sources for the storage and flow heating. Which is odd, since it's inherently suited to using cheap but intermittent heat sources (such as refrigeration waste heat or solar) to heat the water in the tank, and valuable, reliable energy in the flow heater to boost the temperature as needed.
-- spidermother, Jul 13 2011


This seems like it would work, but I'm not sure if it would work well. The coils on the back of the fridge are definitely warm, but they're not too hot to touch.
-- Alterother, Jul 13 2011


There are heat pump hot water systems; assuming it's possible to design a heat pump to operate at, say, 0ºC and 60ºC, a back-to-back refrigerator/hot water system could be built from scratch.

Otherwise, as I suggested, use the fridge waste heat to pre-heat the water in a tank, and boost the temperature with a flow heater. As described, the fridge and water heater are fighting each other.
-- spidermother, Jul 13 2011



random, halfbakery