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03/04/2012

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Bob Lemaire

Marc,

What is the net metering policy with respect to your surplus? Is it use it or lose it?

Also, in the discussion of the R/F do you mean to say the heat gain and compressor energy decreases in the winter? It's subtle but is there a technical reason that you can cite for the apparent increase in efficiency of the hot water heat-pump from August to September?

I'll be curious to see if you go with an electric vehicle. Island life seems like a natural for the range of EVs that are on the market today.

Jan Juran

Hi Marc: interesting data, low usage in Feb. looks like approx 280 gallons DHW used and 100 KWHr to produce. 100 KWHr=341,230 BTUs. At a delta T=60F (50F water supply, 110F DHW) and 8.34 BTU to raise 1 gallon 1F: 140,112 BTU heats 280 gallons (albeit at 100% efficiency). In perfect hindsight, would you consider using several modulating Rheem or Steibel tankless electric HWHtrs (low $200s internet price, plus install cost, <40 Amp typical electricity draw) in the bathrooms and kitchen instead of the Geyser/Marathon in the basement? No wait for HW, 70F water contained within any pipes located in conditioned space=lower delta T, adding a possible DWHR "GFX" plumbed to the shower drains could cut 30-40% off the KWHrs and the Amp draw used for showers.

Marc Rosenbaum

Hi Jan
We have a somewhat higher delta T in the winter, about 70-75F. I don't have the amperage available in my 100A panel for any instantaneous electric. Maybe in new construction...

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