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Residential Refrigerator Power Use

March 29, 2018, 12:21:29 am

Chuck reported some power use measurements in his coach a couple weeks ago.

I decided to do some looking at my power use from my Full River battery bank (4 DC400-6 6v batteries, nominal capacity = 830 amp hrs).  These power my Victron 800VA inverter which runs the residential refrigerator, all of the front end electronics and entertainment equipment and all of the 120v outlets ahead of the kitchen.  Our Samsung 19 cuft french door residential refrigerator is used without the ice make.

I have power use measured at the batteries, after the inverter and for the refrigerator along.

In 385.8 hrs of real world use there was ....
35,725 watts used measured at the batteries. 
    92.6 watts per hour.  2200 watts per day.  At 12.6 volts, 7.35 amps/hour. 176 amp hrs/day.
33,030 watts used after the Victron 800 VA inverter. 
    85.6 watts per hour. At 12.6 volts, 6.8 amps per hour.

And in the 201.2 hrs that the refrigerator use was isolated ....
15,500 watts used just by the refrigerator. 
    77 watts per hour. At 12.6 volts, 6.1 amps per hour.  146 amp hrs per day.

Averages ...
The refrigerator use at 77 watts per hour is about what I expected.
The Victron 800VA inverter uses about 7 watts per hour to be one, about 0.55 amps per hour.
The electronics and entertainment equipment uses 8.6 watts per hour.

The refrigerator is using about 65% of out total power consumed from this battery bank.

Total watts out of the Full River batteries in a typical day is about 2200 watts or about 40% of the 430 amp hrs (5500 watts) available.  That is less than our average solar input.

Roger

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Re: Residential Refrigerator Power Use

Reply #1 – March 29, 2018, 01:34:14 am

Roger, I appreciate your post.  I was surprised the residential refrigerator takes that percentage of your total usage.  I must admit, I had not calculated a residential refrigerator load, even last summer, when I specked out my new solar system with my non residential refrigerator rv.  (Even though I knew one might be in my future).

My reason for not considering this is that I had several rv manufactures tell me, that in their studies, the residential refrigerator used almost the same as a rv type overall, except when in the defrost mode which is when usage went considerably up.  Their reason for this was the energy star rating, which had gotten better each year thru better insulation and efficiency.  They emphasized that with this better insulation, the compressor was seldom being run.  I always took this with "a grain of salt" as one mfg told me it was also ok to use a modified sine wave inverter when I questioned their ms inverter/charger instead of sw.  After replacing several refrigerators that I knew of they went to sine wave inverters.  So much for their engineers and testing befor sale.

I am now, with your data, content with my 560 watt solar and the 3 8Ds with a total of 735 ahs (3@245 when they were new 4+ years ago).  Now I need to study my Remote Meter - Morningstar Corporation and for me, because unstudied, complicated menus.  So far I have just checked on min and max battery voltage, battery temperature, array voltage down from the roof, battery voltage, and amps currently being generated from panels and sun source.  In the future this will help me know if I have an equipment or wiring issue, and #2, help me prolong the life of my batteries.
http://support.morningstarcorp.com/wp-content/uploads/2016/03/MS-001413-A.pdf

Your data confirms what I found on the web:  "The power consumption of domestic fridges is typically between 100 and 200 watts. Over a full day they are likely to use around 1 to 2 kilowatt-hours (kWh) or approximately 350 kWh a year.  The actual energy consumption of your fridge or freezer will depend on many factors."

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Re: Residential Refrigerator Power Use

Reply #2 – March 29, 2018, 07:09:33 am

My favorite.  Factual quantitative info.  Thanks for the work needed to furnish us with this,

While we currently do not have a residential refer the ability to install one is in the back of my mind now that i am gathering pieces for a total solar optimized coach.

Your measured power consumed in amp hours per day and the latest panels 31" width and 62" height for a 245 watt 21.6% efficiency panels might allow me to put even more watra on the roof than I wax originally thinking of. 

Wyatt's reports matches Roger's that with more than 1000 watt of solar that the coach is almost self contained without much if any gen run time,

6 latest panels are around $2,500 range plus installation.

Having the option to run our Dometic and it's freezer side compressor motor and  its icemaker on inverted AC would be nice as we are sort of preppers. 

1500 Watts of solar and maybe another 2 gels would really extend our abilities and lessen our power pole needs even more which would reduce our costs even more and over long term help defray the solar systems costs a bit.

My guru buddy mentioned that when going down the road with a lot of solar that the alternator would be hardly on.  A tiny bit more  power and a bit more mpg to add info the mix.

If more batteries then I might change to a higher output alternator to match. 

I notice that our new solar controller has an off mode. 

Be a good test over a long term to see if the alternator recharging depleted house batteries during a drive versus a large solar roof system makes a mpg difference that's noticeable?

Too many things possible to do and not enough time.  As usual

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Re: Residential Refrigerator Power Use

Reply #3 – March 29, 2018, 10:38:39 am

We do not use the ice maker which is a big energy user.  The Samsung has an economy mode that turns off the defrost cycles.  It is on now when we are where the humidity is higher.  For our use it is usually off.

So on a pretty normal day for us the residential refrigerator uses a bit over 1/2 of our total power consumption.  Solar covers this use (not today, we are 100% cloud cover) on most days. 

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Re: Residential Refrigerator Power Use

Reply #4 – March 29, 2018, 11:23:39 am

Our 10 cuft electric fridge usage measured over continous long periods of time with our Kill O Watt meter.
Fridge is always plugged in, but compressor automatically turns on and off and electric resistance defrost heater automatically turns on and off.
824 hours, 34 days = 23.93 KWh (avg = 0.029 KWh/hr or 29 watts/hour) 1,334 hours, 60 days = 39.06 KWh (avg = 0.027 KWh/hr or 27 watts/hour) 2852 hours, 119 days = 74.68 KWh (avg = 0.026 KWh/hr or 29 watts/hour)

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