E-Star freezers - how so efficient ?

[Cd]

How are Energy-Star appliances such as chest freezers so much more efficient than non E-Star ones ? I have looked at E-star appliances side by side, and see no visual difference ( such as thicker, more insulated walls ) . I suspect the components are just higher quality and made to be more efficient.
Also, after looking at a 5 cu.ft. chest freezer, versus a 8 - 12 ft. model, I see that per square foot of interior space, the larger 10 -12 sq.ft. models are around 30 % more efficient, yet having to cool a larger area within the frig.
Why is this ?
( Both models being the same brand and rating - E-Star / non E-star )

[Daox]

I'd probably say, even though you can't see it, its still insulation. The compressor might be a bit more efficient, but the vast majority of the time the freezer is just sitting slowly warming up.

[dcb]

Any wattage or amperage differences on the labeling?

[Snax]

The efficiency that goes with the larger volume is from the reduced exterior surface area per unit volume.

E.g., assuming a simple model with walls of zero thickness, 10 cube shaped freezers with 1 cu. ft. of total interior volume would have 60 sq. ft. of exterior surface area, a 6:1 ratio, but a cube shaped freezer with 10 cu. ft. of interior space would only have 28 sq. ft of exterior surface area, a 2.8:1 ratio.

In other words, the ten smaller freezers providing the same volume have more than twice the exposed surface area, and twice the thermal leakage.

[Cd]

Originally Posted by Daox

I'd probably say, even though you can't see it, its still insulation. The compressor might be a bit more efficient, but the vast majority of the time the freezer is just sitting slowly warming up.

I'd like to think that this would be the case, however, I tried adding styrofoam sheeting to the sides of my mini frig ( 3.1 cu.ft. ) and it made no difference. The thickness varied between 1.5" - to almost 3" in some areas.
I posted about it here : Turn my 'frig on its side ? - EcoRenovator

[Cd]

Originally Posted by dcb

Any wattage or amperage differences on the labeling?

Slap ! I didn't even think about that !! That's a great idea .
I'll be sure to check that.
Thanks !

[Cd]

Holiday at Lowe's: 7.0 Cu. Ft. Chest Freezer (Color: White)

This 7 cu. ft. chest freezer consumes 277 kWh per year. It is not Energy Star rated.
It is however semi-affordable and ( I think ) able to fit in the back of my Civic hatch.
I wonder just how much electricity it would consume if I converted it to a chest frig.

A Vestfrost SE255 , which is just over 8 cu.ft. uses 172 kWh per year. This is the chest freezer used in this
Man Retrofits Freezer to Make an Ultra-Efficient Fridge : TreeHugger
article to achieve .1 Wh per day.


That's around 84 % less energy consumption than the junk freezer I am thinking of buying.
I assume that this would mean that any conversion that I did with the junk freezer would translate to similar readings compared to the .1 that were from the VestFrost.

So something like around 68 kWh per year compared with the VestFrost at less than 37 right ?

( Please correct my math if it is wrong. )

[Cd]

I wanted to ask about how to solve the frozen foods problem when using a converted freezer. A lot of what I have read makes it sound as if you will end up with a frig that has no ability to store frozen items. ( no more freezer ! )
I did read one response from a poster that was complaining that with a setup like this, you need a fan to keep things on the bottom of the frig from freezing. This seems to solve the frozen foods problem ( just store the frozen foods on the bottom ! ) , but I wanted to confirm this before I buy anthing and start the conversion.

[Snax]

Or perhaps one could just place the sensor at the bottom and store the less perishable items up top.

Oh, but it is very worth noting that temperature stratification does not occur in solids, so a more full fridge of this sort will have less of that to contend with.

[Christ]

Heat rises, cold settles... chest freezers don't particularly need a door.

If you want to mod a freezer, shred up old jeans and replace the normal insulation with them... cotton denim is a better insulator than just about anything.