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?

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

Thank you

A relative told me about Kill A Watt. Seems like it's difficult to only buy one

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.