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HVAC efficency calculation - Moving at the Speed of Procrastination. [entries|archive|friends|userinfo]
E.G.

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HVAC efficency calculation [Jul. 3rd, 2017|01:26 pm]
E.G.
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In good news, the investment we made in having the crawl space "conditioned" seems to be saving energy -- and we keep the place cooler.

Last year we had the thermostat set at 74°F when we arrived, and well before the end of June we increased it 76°F. (We were in shock: i know plenty of folks keep the temp warmer.) This year, since we were told that with the encapsulation we should keep the place at 74°F, i decided we would keep it at that temperature -- on average. Overnight we cool to 72°F, then over the morning we keep the place at 74°F or cooler. It takes a while for the outside to warm up the inside that 2°. Then at noon we let it go up to 76°. The air does run in the afternoon. When the sun gets low behind the pines, we start cooling back down to 74°F.

Looking at spring and fall months, i think i have a good idea of our "no HVAC needed" power load. June 2016 had 8 kwh/d for HVAC, while this June had 5 kwh/d for HVAC. This past June was cooler than 2016 (good, everyone said last year was abnormal). I dug up the number of "cooling degree days" from WeatherUnderground: June 2016 had 1.13 times the cooling degree days than June 2017 but used 1.6 times the power.

So, if i want to get the average amount of power per cooling day (instead of month day), i could calculate

(X kwh/d * Y d)/ Z CDD

to get the kilowatt-hours per cooling degree day. June 2016 is then 14 kwh/CDD and this June is 10 kwh/CDD. That seems a good improvement. 30%-ish?

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