Full fridge or freezer....does it really use less energy?

softdown
softdown Solar Expert Posts: 3,896 ✭✭✭✭
in Off Grid Solar & Battery Systems #1
...or this an "old wives tale"? Lets say there are four refrigerators:
1) Empty
2) 33% full
3) 66% full
4) 100% full
How do they compare for energy usage?

Does somebody know for sure?
First Bank:16 180 watt Grape Solar with  FM80 controller and 3648 Inverter....Fullriver 8D AGM solar batteries. Second Bank/MacGyver Special: 10 165(?) watt BP Solar with Renogy MPPT 40A controller/ and Xantrex C-35 PWM controller/ and Morningstar PWM controller...Cotek 24V PSW inverter....forklift and diesel locomotive batteries
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #2
    The full fridge MIGHT use slightly less power for one reason - - - the thermal storage mass within the full unit would be expected to result fewer compressor starts per 24 hour day, thus fewer start surges. Other than that, once the contents are at a stable temperature, the compressor is required to run only as required to pump out the heat that has filtered in through the insulation or through the opened door etc.
    What will make a difference is the ambient temperature in the area surrounding the fridge, and if the sun is shining on the cabinet, or if the wood stove is radiating heat at it, heating the outside of the fridge, thus driving more heat in through the insulation requiring the compressor to run more often and longer each time it runs.
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  • Dave Angelini
    Dave Angelini Solar Expert Posts: 6,891 ✭✭✭✭✭✭
    #3
    In warm/hot weather, the more you open the door, the increase in moisture will cause the defrost time to increase on newer Tier 3 refrigerators because they have a moisture sensor.
    If you lock the refrigerator door when kids are in the home you probably would save at least a KWH per day.:D
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  • CALLD
    CALLD Solar Expert Posts: 230 ✭✭
    #4
    The biggest effect on the power consumption of your fridge is the dew point temperature of the air in the room and how much time the doors spend open. Condensing water vapor releases an enormous amount of heat - many times more than warm dry air. Filling your fridge with lots of stuff is like adding more batteries to your off-grid system - it won't make you anymore power, but it will give you more run time between charges.
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