O/T Would like an opinion, fact. Full frig or empty. Whats more efficient?

[JRouche]

The reason I am askin is cause we have a small frig in the backyard, rarely used but convenient all the same, so it is gonna stay lit.

The issue is my Wife says it should be run empty until needed (fill with same temp products), less to keep cool.

I think a full box with beverages (Its a bev. frig after-all) would be better. That is if H2O based liquids are better at keeping the box at a certain temp verses just an empty refrigerator box??

What is your take folks??? JR

[portlandRon]

Full is more efficient once the contents are cooled down.

[Evan]

The less often the fridge must start the less energy is wasted during the start cycle. The fuller it is the less often it must start. I keep a couple of gallons of plain water in my apartment freezer so it starts far less often. I also use about 20 to 30% less electricity than the average of users in this apartment building and that is including the 400 watts per hour each night for my oxy concentrator. However, that is just heat and this building is full electric so it really doesn't matter where the heat comes from, all devices are 100% efficient for electric heat generation in winter. In summer it matters.

[Glug]

More efficient, as in requires less electricity?
If it was a furnace, and you wanted to keep it at 300F, then it seems intuitive that the more stuff that's in it, the more energy it would require. Why would it be different for a fridge?

[Evan]

The starting cycle is big energy waster in a fridge. It's drawing power but not cooling for the first few minutes. The fridge warms up faster the less there is in it so the more often it starts.

[A.K. Boomer]

The less often the fridge must start the less energy is wasted during the start cycle. The fuller it is the less often it must start. I keep a couple of gallons of plain water in my apartment freezer so it starts far less often. I also use about 20 to 30% less electricity than the average of users in this apartment building and that is including the 400 watts per hour each night for my oxy concentrator. However, that is just heat and this building is full electric so it really doesn't matter where the heat comes from, all devices are 100% efficient for electric heat generation in winter. In summer it matters.

It's good to have you back Evan!

Glug --- maybe it's a trick question --- if all systems are equalized and then you start to take one month readings on consumption then look at Evans answer cuz it's spot on --- start caps in the motor not to mention all the losses just in transfer delays and such eat it --- the full fridge and freezer win - less overall run time and less start cap engagement --- so if you got a frozen turkey from the store and cold milk and brought it immediately home you will be ahead of the game from the get go,,, maybe not so if you had to freeze a thawed bird or make warm milk cold, but make no mistake there's a time frame where the pay off would start rewarding in favor of the full fridge once again...

use the same theory of operation with the furnace --- in the long haul more crap in your house is actually energy efficient due to thermal storage and the furnace not having to kick on - on a whim,,, longer coast times and yes longer run times - but over all shorter run times for both fan blower and furnace and gas usage due to more efficient transfer --- everything having to do with heating already up to temps and not having to cycle so much and heat up things that do not have much to do with transferring till the snap discs kick in... yet gas is being burnt...

[Evan]

Here is my power consumption compared to others in this building and this is for the middle of summer when the fridge and freezer really matter. It is also when I do not win from running the oxy machine. I still do far better than the others. I use LED lighting, turn down the hot water to 120F and keep the fridge and freezer full.

[A.K. Boomer]

Don't forget also the power consumption from running the printing machine almost 24/7


There is not just an efficiency benefit from a full fridge and freezer - there's also the increased life to the appliance to consider...

[darryl]

It's going to use more energy to get a full fridge down to temperature, but then it uses energy based partly on how well it keeps the cold in. That's not a function of the contents, but of the insulation, seal effectiveness, and design. What Evan said is true- the more often it has to go through starting and establishing the cooling process, the more energy is wasted.

I have another take on it as well- an empty fridge is full of cooled air. When you open the door, cool air drops out and is replaced by warm room air. That air now needs to be cooled. If the fridge is mostly full, there's less air for one thing, plus lots of obstacles to slow down the air flow out of the fridge- so less loss of cool.

It is interesting that all the energy being used by an electric appliance of any kind is lost into the room, where it supplements the heat being produced by the furnace or electric heating. If you use electric heat, then in essence anytime you need to heat you could consider that all of your electric appliances are being run for no cost- if not for them running your electric heaters would have to draw more juice. Same thing goes for the number of people in the house- the more there are, the more heat goes into the room from the metabolic process of living. Of course this is offset by how many times they open the fridge and open outside doors.

[A.K. Boomer]

.


It is interesting that all the energy being used by an electric appliance of any kind is lost into the room, where it supplements the heat being produced by the furnace or electric heating. If you use electric heat, then in essence anytime you need to heat you could consider that all of your electric appliances are being run for no cost- if not for them running your electric heaters would have to draw more juice.

Spoken from somebody who lives far north --- summer time hits around here and if somebody is using AC then it's a double wammy in the inefficiency department...

[J Tiers]

Overall, it should not really matter.

The inside is at temperature "X", the outside at temperature "Y".

With a given type and amount of insulation, there is a certain flow of heat energy through that insulation per hour. That heat energy must be extracted from the inside about as fast as it comes in, so that the inside does not warm up too much. But the "leaking" heat energy must be pumped out or the inside will change temperature. If it stays at a given temp, there is a balance between the rate of heat leaking in, and heat being pumped out.

The flow of heat is no different whether the thing is full or empty, it is only the difference in temperatures that counts. Perhaps there is a temporary difference if the thing is packed full, simply due to the ability (or not) of heat energy to get into the area of the thermostat. But the balance must be kept, or the inside changes temp.

Then also, the temperatures count in a different way when you talk of efficiency. The heat pump used to cool it becomes less efficient as the difference in temperature is larger, and also is to some extent dependent on the absolute temperature into which heat must be rejected.

With a lot of high heat capacity stuff, like water, in it, the fridge turns on less often, simply because a given amount of heat energy changes the temperature less, so the fridge runs less often. But when it does run, it will have to run longer, to get the heat out of that mass of material.

If there is any difference in efficiency, it can only come from a difference in run time. The actual heat energy being moved around is the same whichever way you load it.

[Mike Amick]

The flow of heat is no different whether the thing is full or empty

I don't think this is right. if the fridge is totally empty and you leave the door open, it is going to warm up
in there much fast than if every square inch was stuffed with very cold anything else.

[Evan]

"The flow of heat is no different whether the thing is full or empty,"

Nope, there is a very big difference. To get warmer with a full fridge a lot more stuff must warm up including the two gallons of water in my freezer.

[becksmachine]

"

Nope, there is a very big difference. To get warmer with a full fridge a lot more stuff must warm up including the two gallons of water in my freezer.

Yes, given any consistent temperature differential, the TEMPERATURE of that mass will increase faster with less mass to warm up.

But this is only because it takes less ENERGY (power) to raise the temperature of less mass.

Which means it took less energy to extract that heat in the first place. Consequently, the flow of ENERGY through a given barrier (insulation) is consistent with a consistent temperature differential.

Temperature is not, by itself, a measure of energy.

Dave

[Black_Moons]

It's going to use more energy to get a full fridge down to temperature, but then it uses energy based partly on how well it keeps the cold in. That's not a function of the contents, but of the insulation, seal effectiveness, and design. What Evan said is true- the more often it has to go through starting and establishing the cooling process, the more energy is wasted.

I have another take on it as well- an empty fridge is full of cooled air. When you open the door, cool air drops out and is replaced by warm room air. That air now needs to be cooled. If the fridge is mostly full, there's less air for one thing, plus lots of obstacles to slow down the air flow out of the fridge- so less loss of cool.

...

Exactly my thoughts, a fridge filled even with just empty jugs is going to consume less energy to recool itself after you open and close the door.

Evan has a point with how long the fridge takes to cycle however, if the fridge is not opened very much that effect is likely to dominate.

Of course, Both effects say that a full fridge is going to take less energy to maintain.