EcoRenovator - View Single Post - Low cost DIY AC/fridge duty cycle and dryer and water heater kWh estimator

MN Renovator · 09-04-14, 02:24 PM

Since I bought my house, I've worked a shift that requires a 7 day(as opposed to a weekday/weekend thermostat) because of a 4 day workweek. When shopping for a thermostat I found models that count the call for heating and cooling in hours and minutes. It shows today, yesterday, this week, last week, and since last reset. I reset it at the start of the billing cycle and can get spot on with the heating cost and for the cooling I can get a pretty close guess.

Low cost TED units, I got mine for $20 on ebay, are good for cumulative kwh metering. I'll be installing an e-gauge for my solar system and will also install additional sensors to monitor the AC compressor(will soon integrate a more efficient mini-split heat pump that will be measured). If you want a revenue grade meter, you can get them from Hialeah Meter Company I like the TED, e-gauge, etc. type unites though because you can see real time usage which helps with working down your base load at the whole house power use level which works great in conjunction with Kill-a-watt type single outlet meters.

I used a kill-a-watt to determine the duty cycle for my fridge and it works just fine, the compressor is always between 145-150 watts after it has been running for its initial minute. It seems remarkably consistent with the on and off times if the door remains closed with the same ambient temperatures so measuring 4 cycles or so with a stop watch and you've got the average duty cycle down pretty close. As an example, my fridge runs for 10 minutes and the cycle starts every 38 minutes. It consumes just under a kwh a day. Depending on the indoor dew point and how often I open the fridge, I'll kick the defrost on every other week which consumes about 225wh to defrost with the 600 watt element usually running for 15 minutes and a 30 minute compressor cycle to catch up. This is a side-by-side ice through the door, non energy star unit. Disabling the 10 hour automatic defrost(timer was running off of clock time, not compressor time) was the best thing I've done for it because it has cut the energy use down to about 80% of where it was before.

Hope this helps.

09-04-14, 02:24 PM	#6
MN Renovator Less usage=Cheaper bills Join Date: Nov 2010 Location: Minneapolis, MN Posts: 939 Thanks: 41 Thanked 116 Times in 90 Posts	Since I bought my house, I've worked a shift that requires a 7 day(as opposed to a weekday/weekend thermostat) because of a 4 day workweek. When shopping for a thermostat I found models that count the call for heating and cooling in hours and minutes. It shows today, yesterday, this week, last week, and since last reset. I reset it at the start of the billing cycle and can get spot on with the heating cost and for the cooling I can get a pretty close guess. Low cost TED units, I got mine for $20 on ebay, are good for cumulative kwh metering. I'll be installing an e-gauge for my solar system and will also install additional sensors to monitor the AC compressor(will soon integrate a more efficient mini-split heat pump that will be measured). If you want a revenue grade meter, you can get them from Hialeah Meter Company I like the TED, e-gauge, etc. type unites though because you can see real time usage which helps with working down your base load at the whole house power use level which works great in conjunction with Kill-a-watt type single outlet meters. I used a kill-a-watt to determine the duty cycle for my fridge and it works just fine, the compressor is always between 145-150 watts after it has been running for its initial minute. It seems remarkably consistent with the on and off times if the door remains closed with the same ambient temperatures so measuring 4 cycles or so with a stop watch and you've got the average duty cycle down pretty close. As an example, my fridge runs for 10 minutes and the cycle starts every 38 minutes. It consumes just under a kwh a day. Depending on the indoor dew point and how often I open the fridge, I'll kick the defrost on every other week which consumes about 225wh to defrost with the 600 watt element usually running for 15 minutes and a 30 minute compressor cycle to catch up. This is a side-by-side ice through the door, non energy star unit. Disabling the 10 hour automatic defrost(timer was running off of clock time, not compressor time) was the best thing I've done for it because it has cut the energy use down to about 80% of where it was before. Hope this helps.