How to calculate usage of a refrigerator?

[tim126]

How to calculate usage of a refrigerator?

I am using a refrigerator (model No FRT18SJGW1) given by my landlord, which consists of a freezer compartment on the top and a bigger fridge compartment below. There are two questions I would like to ask you guys:

1. There is a label in its fridge compartment saying:
Electrial ratings: Amps 4.75, Volts 115, Hertz 60

I tried to compute its energy usage per year, and here is my computation:
4.75 Amps * 115 Volts * 0.001 * 24 hrs * 365 days = 4785.15 kWh/year

I looked up its model No FRT18SJG*1 (FRT18SJGW1) on www(dot)energystar(dot)gov(slash)index.cfm?fuseaction=refrig.calculator, and found that it uses 766 kWh/year.
Sorry for the inconvenience in the link (I am not allowed to post URLs to other sites because I haven't made 15 posts or more）.

Although I know both my computation and the website are estimates, they are too far different. What has been wrong? How can I do the calculation correctly?

2. I was also wondering what the refrigerator's power should be like after being used for 12 years, and if the amount 766 kWh/year shown at energystar website has taken into account the age of the refrigerator?

Thanks and regards!

[Brian_UK]

You are calculating your estimate based on 24 hour running.

The compressor will only be operating for a percentage of that time. Once the fridge is down to the set temperature the compressor switches off until the temperature rises again.

Hope this helps.

[acnerd]

Hello Tim, your calculation appears ok. I am not sure of how the current works on lower voltages in the USA. We run on 230V in the UK. So just wondering whether that compressor will continously draw over 4A during the ON cycle, or if that is just the maximum start-up current.

Which leads me to the next point: the compressor shouldn't be running 24 hrs a day, 365 days per year. Not sure on the ON/OFF ratio. Depends on the ambient it runs in, how often you restock it, open the door, etc.

Maybe someone else can be more specific.

[tim126]

Thanks, Brian!

I was wondering where to get some sense of the percentage value of the working time of the compressor, and how to take it into account for the computation?

You are calculating your estimate based on 24 hour running.

The compressor will only be operating for a percentage of that time. Once the fridge is down to the set temperature the compressor switches off until the temperature rises again.

Hope this helps.

[tim126]

Thank you, acnerd!

Anyone has idea about how the age of the refrigerator affect its electrical usage?

[chemi-cool]

It is calculated for 18 hours work per day.

[mikeref]

Tim126, running time of your fridge will depend on MANY factors though in Australia for a 0 to 4yo averages 12 to 14 hrs/24. As the fridge ages and insulation fails its common for them to run the compressor 16+ hrs/24. If your fridge is a frost free model, your calculations will have to include heater run time ( for defrost ) which is around 8 to 25 mins depending on manufacturer, cheers, mike

[nike123]

To many variables in that computation. You will never find exact number. Energy star is assumption based on average use.
Buy power meter and find your real consumption.