DC Fridge or AC fridge with inverter?

[Bud Martin]

Yes, watt hours - size is 100 litres - which google says is about 3.5 cubic feet

3.5 cubic feet using 600WHr (0.6KWH) per day? That seems a lot.

 

[trevor.the.van]

3.5 cubic feet using 600WHr (0.6KWH) per day? That seems a lot.

Compared to my experience with DC fridges, they would use about 400 per day. And the DC fridges I've used are half the size.

 

[OnTheRoadAgain]

227 Wh / 10.1 hours = 22.4 Watt Hours (per hour?) in a 10 hour period

Battery capacity is 26Ah. Plenty of run time even on a small battery
Totally acceptable

Just over 2 hours to replace that energy with one 100Watt solar panel.

 

[alfaeric]

Thanks for the data!!!

While your example fridge is too small, it does very much give one something to think about- especially at some point, the small compressors for small fridges will reach a min limit- so somewhere in the small size area, the compressor narrows down to one version.

So then the question becomes- how to shop for a 'fridge and an inverter that results in a very good result?

A side question- is there a simple accessible output that one can tap into to use as a fan switch? So that I can put a small 12V fan on the heat exchanger to help it work better? My DC fridge has that, and given it's put into a constrained place, that's a good (and cheap) thing to add.

For sure, if this fridge I have dies, I will lean toward a small AC fridge with an appropriate inverter.

BTW, setting up inverter vs. shore power would be as easy as a switch that goes between one and the other. Especially if it's a 3 way switch to allow the fridge to power down between inverter and shore power.

 

[OnTheRoadAgain]

Thanks for the data!!!

While your example fridge is too small, it does very much give one something to think about- especially at some point, the small compressors for small fridges will reach a min limit- so somewhere in the small size area, the compressor narrows down to one version.

So then the question becomes- how to shop for a 'fridge and an inverter that results in a very good result?

A side question- is there a simple accessible output that one can tap into to use as a fan switch? So that I can put a small 12V fan on the heat exchanger to help it work better? My DC fridge has that, and given it's put into a constrained place, that's a good (and cheap) thing to add.

For sure, if this fridge I have dies, I will lean toward a small AC fridge with an appropriate inverter.

BTW, setting up inverter vs. shore power would be as easy as a switch that goes between one and the other. Especially if it's a 3 way switch to allow the fridge to power down between inverter and shore power.

The next test will be on the 3.1 Cu ft fridge in the garage.
It's the next step up in Mini AC fridges
It's THE ONE I really wanted to use......but my current "campermobile" is only a dodge caravan.

 

[6269ed]

I recently bought a DC only fridge for a friend who was going off grid for a couple months and was able to test it for a month and I was shocked at how little power it used, it was consuming less than 300 watt hours in 24 hours off 2 6v batteries , less than 20% of batteries usable capacities. And as long as the sun was out I could have the battery fully charged back up with a 120 watt panel add a second one for most cloudy days .and this was during mid February - March .
This unit is a ever chill stand up fridge freezer combo ,not a full size refrigerator but still I think I could live out of it no problem. Its a lot bigger than a mini fridge.
Cost was just under 1000.00 from Amazon

 

[Bud Martin]

I recently bought a DC only fridge for a friend who was going off grid for a couple months and was able to test it for a month and I was shocked at how little power it used, it was consuming less than 300 watt hours in 24 hours off 2 6v batteries , less than 20% of batteries usable capacities. And as long as the sun was out I could have the battery fully charged back up with a 120 watt panel add a second one for most cloudy days .and this was during mid February - March .
This unit is a ever chill stand up fridge freezer combo ,not a full size refrigerator but still I think I could live out of it no problem. Its a lot bigger than a mini fridge.
Cost was just under 1000.00 from Amazon

It uses only 300Wh per day? That means it consumes only 300W/24h= 12.5W each hour for 24 hours, that is really low power consumption.

 

[ScoTTyBEEE]

here’s a dc vs ac test

 

[ed6269]

I bou

It uses only 300Wh per day? That means it consumes only 300W/24h= 12.5W each hour for 24 hours, that is really low power consumption.

Yep I was shocked when I looked at the watt meter , 2 - 6 volt lead acid batteries would run this unit for a week with no sun and when I hook up 2 - 120 watt panels whether its cloudy or not it tops the batteries off by the end of the day in March. Could not believe it. When I run my AC fridge and freezer the batteries are depleted in about 12 hours (I have never ran the fridge by itself to see how much longer it would run) In 12 hours thats about 1200 watt hours of use.

 

[Bubba1]

I've been looking for a while and might buy this one . https://www.amazon.com/dp/B07TLL68BG/ref=cm_sw_r_cp_apa_i_X4EA8PJ870ZQGDD4YYXB?_encoding=UTF8&psc=1. Good compressor.

 

[Bud Martin]

I bou

Yep I was shocked when I looked at the watt meter , 2 - 6 volt lead acid batteries would run this unit for a week with no sun and when I hook up 2 - 120 watt panels whether its cloudy or not it tops the batteries off by the end of the day in March. Could not believe it. When I run my AC fridge and freezer the batteries are depleted in about 12 hours (I have never ran the fridge by itself to see how much longer it would run) In 12 hours thats about 1200 watt hours of use.

My home 20+ years 26 cu.ft side by side fridge uses 2080Wh per day measrued on the AC side of the inverter, so if factor in the conversion lost, I figure 2400WHr on the dc side of the inverter.
So to compare power consumtion based of cu.ft/Wh:
I.E. if 3 cu. ft uses 300Wh, then at 26 cu.ft, it will use 8.67 * 300Wh = 2601Wh.
Notes: 26cu.ft./3cu.ft = 8.67
But of course I will not have 26 cu. ft fridge at the cabin, too big.

 

[6269ed]

My home 20+ years 26 cu.ft side by side fridge uses 2080Wh per day measrued on the AC side of the inverter, so if factor in the conversion lost, I figure 2400WHr on the dc side of the inverter.
So to compare power consumtion based of cu.ft/Wh:
I.E. if 3 cu. ft uses 300Wh, then at 26 cu.ft, it will use 8.67 * 300Wh = 2601Wh.
Notes: 26cu.ft./3cu.ft = 8.67

I just checked the fridge size and it is 11 cubic foot size . Its not a small unit but its smaller than my fridge in the house but bigger than a mini fridge

 

[Bud Martin]

I just checked the fridge size and it is 11 cubic foot size . Its not a small unit but its smaller than my fridge in the house but bigger than a mini fridge

That is not small size like those used in the dorm, it is really amazing that it uses so much less power.
Do you have the link to the AMZ?

 

[6269ed]

I am not very computer savvy so I don't know how to post a link but if you search Amazon for Ever Chill Model #WD-282FWDC it will come up for 999.90

 

[HRTKD]

I think this is the model:

https://www.amazon.com/Everchill-Cubic-Foot-Volt-Refrigerator/dp/B08R6BWW7M

The manufacturer's website, but it doesn't tell you much more than the Amazon page:

11 Cubic Foot 12 Volt Refrigerator, Stainless Steel

The Original 12V RV Refrigerator Upgrade your RV’s comfort and convenience with the industry’s first 12-volt refrigerator. Store more and keep your cold foods fresh with Everchill by Way’s 11 Cubic Foot 12-Volt fridge, the first engineered and designed for use in a recreational vehicle. The...

www.wayinterglobal.com

The dimensions (59.73" x 25.72" x 23.58") are almost exactly the same as my Dometic 8 cu ft gas/electric refrigerator in my RV (60-5/8"H x 24-11/16"W x 24-7/8"D).

 

[6269ed]

I think this is the model:

https://www.amazon.com/Everchill-Cubic-Foot-Volt-Refrigerator/dp/B08R6BWW7M

The manufacturer's website, but it doesn't tell you much more than the Amazon page:

11 Cubic Foot 12 Volt Refrigerator, Stainless Steel

The Original 12V RV Refrigerator Upgrade your RV’s comfort and convenience with the industry’s first 12-volt refrigerator. Store more and keep your cold foods fresh with Everchill by Way’s 11 Cubic Foot 12-Volt fridge, the first engineered and designed for use in a recreational vehicle. The...

www.wayinterglobal.com

Yep thats it , it uses less than 300 watt hours in 24 hours and the highest amp draw has been 9.13 amps and while running its usually between 35 and 70 watts , when you first plug it in it will draw 112 watts for a minute but after that it stays between 35 and 70 watts but most of the time it is zero watts

 

[HRTKD]

Can you clarify the total number of watts used in 24 hours in your test? I'm confused by your use of watt hours.

The mfg says average draw is 6 amps. 6 amps per hour? If so, then ~72 watts per hour, 1728 watts per day or 144 amps per day. If those numbers are correct, that's an efficient refrigerator and I might consider it.

 

[Bud Martin]

Good looking fridge.

 

[OnTheRoadAgain]

Yep thats it , it uses less than 300 watt hours in 24 hours and the highest amp draw has been 9.13 amps and while running its usually between 35 and 70 watts , when you first plug it in it will draw 112 watts for a minute but after that it stays between 35 and 70 watts but most of the time it is zero watts

528watt hours is just about what my AC fridge used in the 24 hour test I did yesterday. I'm pretty sure

Certainly not as good as a DC fridge. But......

Let's say your fridge ran in between your 35 and 70watts at 52watts. That's a little more than my AC fridge at about 40watts or so.
My little AC fridge pulled about 4 AC Amps when running.

And lets say it has a 40% cycle rate (60% of the time off and 40% of the time on.
(My fridge cycles about 50% of the time so it could just be an insulation difference here?

40% of 24 hours is 9.6 hours running @ 52watts = 499Watt Hours.

So that DC fridge (albeit larger) is drawing about the same power per day as the mini AC fridge.
unless my math is way off ( always possible)

I was thinking of wrapping my little low budget AC fridge in an insulation wrap and trying aqain just to see.

 

[Luthj]

The biggest factor is insulation. Followed then by compressor design. This assumes good condenser air flow.

If you have 8" if insulation on a 1,000l fridge it could use less power than a 100l fridge with 2.5" of insulation. Assuming you don't open the door or put warm food in it. About 1/3 of my fridge power consumption is cooling food thats put in it.

On the inverter side a low standby power inverter, or one switched by the thermostat will only add about 10-15% power consumption overhead.

However large inverters are not very efficient at low loads. My 3kw unit needs 400W of input to make 300W of output. While it only needs 2,100W to make 2,000W.

 

[OnTheRoadAgain]

The biggest factor is insulation. Followed then by compressor design. This assumes good condenser air flow.

If you have 8" if insulation on a 1,000l fridge it could use less power than a 100l fridge with 2.5" of insulation. Assuming you don't open the door or put warm food in it. About 1/3 of my fridge power consumption is cooling food thats put in it.

On the inverter side a low standby power inverter, or one switched by the thermostat will only add about 10-15% power consumption overhead.

However large inverters are not very efficient at low loads. My 3kw unit needs 400W of input to make 300W of output. While it only needs 2,100W to make 2,000W.

I think you're right about the insulation.

I used a 1000Watt inverter and it measured 400mA draw at idle

The efficiency is claimed to be 90% or greater. I believe it is greater than 90% after testing

It's music to my ears that I can have at least some kind of refrigeration in my mobile HQ until I can plunk down the 1000 clams for a DC fridge. If I do.

 

[6269ed]

Can you clarify the total number of watts used in 24 hours in your test? I'm confused by your use of watt hours.

The mfg says average draw is 6 amps. 6 amps per hour? If so, then ~72 watts per hour, 1728 watts per day or 144 amps per day. If those numbers are correct, that's an efficient refrigerator and I might consider it.

If you had a 100 watt light bulb and turned it on for 1 hour it would use 100 watt hours.
The manufacturer told me the same thing that the unit used an average of 6 amps when I wanted to know the max amp draw so I could have a cigarette lighter style power source rated on my buddys bluetti EB240 (Which has a rating of 9 amps) so his info was useless to me , fortunately the fridge only draws 9.13 amps and that is just for a minute so the EB240 powers it no problem . I don't know if it draws 6 amps an hour all I can tell you is it doesn't use near the power a AC fridge uses with my 3000 watt inverter.

 

[HRTKD]

I was thinking of wrapping my little low budget AC fridge in an insulation wrap and trying aqain just to see.

As long as the coils are on the back and you don't block them. Newer residential refrigerators have the coils in the sides of the refrigerator, so spacing between the side of the refrigerator and the wall is important.

 

[OnTheRoadAgain]

If I can insulate this thing better and get it down to 250 - 300watt hours for 24 hours it'd be icing on the cake.

 

[rcrracer]

If thinking about a high efficiency chest freezer converted into a refrigerator, download the Excel file at https://www.energystar.gov/productfinder/product/certified-residential-freezers/results. Add another column or two to determine something like watts per cu. ft. You should find that it is more efficient to buy a chest freezer >= 14.8 cu. ft. Hypothetical example: A 15 cu. ft. freezer uses x watts per year. A 7.5 cu. ft. freezer(1/2 half the size) uses .75x watts per year. A small amount of efficiency over the >= 14.6 cu. ft. can be had with even larger freezers. The gains are near as great as with a >= 14.8 cu.ft. freezer (This was true doing the calculation about five years ago and I'm assuming things are still the same.)
There isn't any reason a chest freezer can't be converted to a freezer at one end and a refrigerator in the volume that remains.
Upright refrigerators w/freezers and upright freezers seem to use more electricity not only because they may have less insulation, but also to the fact they all have defrost cycles.