> *-Because a heat pump system is using energy to "move" existing heat, > it gives you 400% (or more!) efficiencies. [i.e. you use 800 watts to > drive a compressor and fans, but get 3,200 watts of heat into the > tank, while cooling the area around the water heater.]
I think it is more like 3 to one. The higher temp you want the water, the lower the efficiency and can range between 2 to 1 or 4 to 1. > I haven't shopped for heat pump water heaters. It looks like I should. > I have recently resolved to stop using my propane water heater... Here is my summary. They are often called HYBRID water heaters with the heatpump heating the incoming water at the bottom of the tank and then (if enabled) a resistance element at the top to provide rapid response and higher temperatures. Remember the heatpump is the most efficient when it is throwing energy at the incoming 60F water with a greater delta-T The efficiency goes down as the temperature rises. SO I have mine set to heat the bottom of the tank to only 105F (where it is still pretty efficient) and then the top coil heats the rest to 115F. IN fact, I really have the Heatpump one in series with the old pure electric one and both have an added 4" insulation around them. So I let the heatpump one heat its entire tank to 105F, from there it goes into the old heater which has the bottom element turned off and the top element set to 115F. SO the bulk of the heating (55 to 105F (50 degrees) is done at 3:1 electric effdiciency, and the final 105-115 (10 degrees) is straight electric at 1:1 (but saves wear and tear on the heatpump, working much harder j ust to get the final 10 degrees). Remember you can drastically change the "capacity" of a water heater simply by the temperature setting. If you set it to 140F, then when you take a shower, you only use a little bit of hot water mixed with more cold water to get to final temp. This gives you a lot of "hot" water capacity. If you don't use that much hot water, then set the temperature to 110F, but now then your shower will be using mostly hot water from the tank and only using a little bit of cold water. Now your capacity is much less but you save energy by not throwing a higher temperature away mixing it all with cold water. Your wife may vary. Bob http://aprs.org/Energy-Choices.html _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
