Posted: 5/8/2024 10:15:03 PM EDT
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Fridge is rated at 481 kWh/yr. Trying to figure out watt-hours or to me an estimate of how many consecutive hours I can use the fridge for. I went about this two ways which gave me different numbers: 481 kWh/year DIVIDED BY 365 days/year = 1.317 kWh/day 1.317 kWh/day TIMES 1000 watts/kWh = 1317 watts 1317 watts DIVIDED BY 24 = ~54.9 watts Am I correct in thinking 1317w is startup/surge power whereas 54.9w is the estimated amount of watts used per hour? At first I was using 2000 watts (battery capacity) DIVIDED BY 1317 watts/hour = 1.52 hours. The latter seemed a bit high as I could only run the fridge for 1.5 hours? |
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Those numbers are in line. I had an old chest freezer and it averaged about 75watts an hour. An old refrigerator was about 100 watts. (it actually drew about 250 watts when running, but was running less than half the time) A new Energy Star chest freezer averages about 45 watts an hour. Get one of these! https://www.amazon.com/P3-International-P4460-Electricity-Monitor/dp/B000RGF29Q The newer version has a battery (maybe capacitor) backup that'll remember how much electricity was used up to the point of power going out. I've used that to get a measure of how much electricity a gallon of gas actually produces  |
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Buy a kill-a-watt, then test under the worse conditions that you think you will experience (no power/no HVAC), so that the estimate is close to reality. For example, I tested my deep freezer in the garage during the spring and it used around 0.64 KW per day. When I tested it during the summer, it was using around 2 KW per day. Also, you won't get 100% from the battery due to inverter loss, so you will want to find out the inverter efficiency to include in your calculations. |
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Originally Posted By Scalped: Fridge is rated at 481 kWh/yr. Trying to figure out watt-hours or to me an estimate of how many consecutive hours I can use the fridge for. I went about this two ways which gave me different numbers: 481 kWh/year DIVIDED BY 365 days/year = 1.317 kWh/day 1.317 kWh/day TIMES 1000 watts/kWh = 1317 watts 1317 watts DIVIDED BY 24 = ~54.9 watts Am I correct in thinking 1317w is startup/surge power whereas 54.9w is the estimated amount of watts used per hour? At first I was using 2000 watts (battery capacity) DIVIDED BY 1317 watts/hour = 1.52 hours. The latter seemed a bit high as I could only run the fridge for 1.5 hours? I'm only trying to help. This is not meant as a put-down or criticism. This is an example of needing to keep correct units of measure in order to keep your thinking straight and to make correct conclusions. 1.317 kWh/day = 1317 Wh/day <-- NOT "watts", it is the daily average energy consumption, not power 1317 Wh/day / 24 h/day = 54.9 W <-- this is the daily AVERAGE power consumption, it is NOT peak power or energy. Your "1317" figure is NOT the startup or surge power, it is not a power level, at all. This is a mistake caused by watching numbers but failing to follow the units of measure. Your "54.9 W" is the daily average power consumption. It tells you nothing about the power required to start the compressor or to power the refrigerator when it is running. That daily average includes all the time during the day during which the refrigerator is off. Battery capacity is measured in Ampere-hours, not Watts. Battery energy capacity is in Wh, not W. The rest of the battery discussion is undecipherable to me due to these basic errors. In no case is your "1317 W/h" a valid figure or units of measure. The 1317 figure is 1317 Wh/day. Did you mean 2000 Ah or 2000 Wh for the battery capacity? Be careful with battery energy storage, as energy is dependent upon discharge rate - low rates yield max energy, high rates can yield significantly less. I cannot help much more here because the important info is missing. Look at the back of your refrigerator. There will be info about power consumption when it is running. Sometimes it also tells you the start up power requirement (unusual). Power to start can be as high as 2X running power. |