Help with energy guide conversion

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surfmore72

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I wish to power a 110v device off of a battery.   I'm shopping online for it and can only get the yellow energy guide specs.   172kWh/yr.   So assuming 80 % efficiency to 12v conversion that brings the total to 206/yr.   Braking it down to 564 watts per day or 24watts per hour(on average). 
Is this all making sense?   So that's like 0.3 amps per hour or 7.2 amps per day?   Does that all work out?   
Thanks
 
No, more like 3A per hour and 72Ah per day for your prospective dorm fridge.

The amp figures are on 115Vac, not 12v DC so volts x amps = watts means you have 12v vs 115V, and need to slide that decimal point over.

Actual consumption figures will vary greatly depending on ambient temperature, how often you load it with warm items/open the door, actual inverter efficiency and the ventilation the cooling unit is allowed, and the insulative abilities of the cabinet that it resides within, if any.

While dorm fridge on the inverter can and does work, usually it requires twice the battery capacity and twice the recharging capability, thus usually negating any cost savings of a dorm fridge over a 12v compressor fridge.

Also one needs to factor in the inverters standby load to the consumption figures. The fridge might run 15 minutes out of each 60, but the inverter will be using some figure just turned on waiting for the compressor to fire back up.

Standby inverter loads vary greatly.

I have a 800 watt MSW inverter that draws 0.68 amps turned on powering nothing.

0.68AH is more than my 51 liter 12v compressor fridge consumes in an hour 80% of the time.

$ticker $hock of 12v compressor fridges sends many people down the 120v dorm fridge on inverter path.
Most regret this choice.

Factor in the doubled battery capacity, larger inverter required and double the amount of solar into the dorm fridge equation and the 12v compressor fridge's pricetag is not as unpalatable.
 
Thanks for the quick response!   I have a few ac devices to power and was hoping to better understand the math so I don't have to keep bugging y'all. (i know the fridge thing is well debated already) 
Where does the 3 amps come from?   I divide 24watts by 115 and get 0.21amps  (i rounded to 0.3 for power loss in wires and such).  
 Thanks again!   The initial power usage energy guide of 172Kwh /yr  figure is from an energy star chest freezer for what it's worth.
 
since you'll be powering it from a 12v system, it's 24 watts divided by 12v = 2.0 amps
 
that .3 is for 115v. basically when you run it off 12v you multiply the .3 by 10. 90% of the time it's better to run everything you can off of 12v. for every conversion you have losses. highdesertranger
 

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