Comparing the Power Consumption of a 30 Year Old Refrigerator to a New One

In one case, during the high summer, I didn't notice one was slowly getting warmer. I had constant bowel problems, because I was eating rotten mayonnaise. This was compounded by the fact that I bought fancy spicy mayonnaise, which I'd never tasted before, which masked the rotten flavour.

So -- my lessons learned, never by LG horrible fridges again, and keep an analog thermometer, which I bought for $5, in the fridge.

(General FYI, LG has had more than one class action law suit because of their compressors, and, they even make it very hard to obtain replacements. Evil bastards.)

My point is, you should take care with any fridge, new or old.

(edit: some clarity on mayo)

You’re presumably thinking of the “Affinity Laws”, which, according to Wikipedia (and plenty of other sources), “apply to pumps, fans, and hydraulic turbines. In these rotary implements, the affinity laws apply both to centrifugal and axial flows.”

This is, IMO, one of the worst kinds of science writing. Wikipedia, and plenty of other sources, make little mention of when the do and don’t apply or, relatedly, why they’re true and why they can’t always be true.

They generally apply to situations where a pump is pumping fluid through something like a filter or a long pipe where the pipe is a closed loop or at least the ends are at the same elevation (e.g. a swimming pool pump, except when pumping from a pool into a higher hot tub). So you have no actual work being done by moving fluid, and you can run the pump slower, and thus move less fluid per unit time, thus reducing friction in a manner that the pressure that the pump needs to overcome goes all the way to zero as the flow rate approaches zero.

But the affinity laws are not really anything fundamental about pumps, and they certainly do not override conservation of energy.

Now consider a refrigerator. The compressor is pumping refrigerant from an (approximately) fixed low pressure to a fixed high pressure. (The fluid goes back from high pressure to low pressure via a capillary tube or expansion valve or similar lossy device -- it gets its pressure increased in the gas phase and decreased in the liquid phase.) There's some friction, but after subtracting friction, the pressure is independent of flow rate, and thus the work done per unit flow is independent of flow rate, and the pump power scales linearly with flow as opposed to super-linearly as the affinity laws suggest.

Also, the compressor is a positive-displacement pump, and the affinity laws don't even pretend to apply to these.

(A well pump is another common system where the affinity laws will lead to nonsensical results. If you want to size a well pump properly, you need to know the height that you're raising the water, the output pressure you need, and the range of flows that you want. And then you look at the actual measured performance curves of the pumps (and their drives) that you are considering, and you pick something appropriate.)

All that being said, variable-speed fridges exist, and they're kind of nice in that they try to run continuously and quietly instead of alternating between full-power (and loud) and all the way off. And they are probably a bit more efficient because there's less friction and because the motors are likely to be more efficient three-phase designs instead of the not-actually-amazing single-phase motors you'll find in older fridges.

Properly sized multistage A/C systems are a much better idea.

Here's the full clip: https://www.youtube.com/watch?v=ioyU_sZufC8

But at the end of the day the question is what is the likelihood the old fridge will be in a semi-broken state.

The Montreal protocol (1987) put us back into the dark ages with coolants for a while (both with CFC ban and later phase outs of HFCs). I suspect if you tested a refrigerator from 40 years ago they would give modern ones a run for their money...

It was obviously a worthwhile sacrifice for the ozone layer though.

There are better insulations out there, but they cost money and are harder to work with. For example, we could theoretically vacuum seal a fridge, but that'd require an airtight seal and likely a stainless steel structure around the fridge.

There are some like ComEd that you call out that can apply the model to residential rates, though my (now dated) experience is that they are rarer.

I will also point out that the way inflation has tended to work is that you can still buy high quality appliances and other consumer products (e.g., tailored clothes and built-to-last leather shoes), but when you do the inflation math you have to spend a lot to get the equivalent product from decades ago.

In other words, the same quality products generally still exist, the real issue is that a bunch of low price products that didn’t used to exist now do, and average people didn’t own as much stuff as they do now.

If you buy a $2500 Speed Queen or a $10,000 Sub-Zero you’re getting the kind of quality and repairability that used to exist in more appliances.

But when it comes to a $500 washing machine or dryer, when you adjust for inflation that product did not exist 40 years ago.

The other thing I’ve heard about this issue is that the mid-range consumer luxury type stuff is the segment to avoid: built cheaply but with a lot of features that fail and a high cost. E.g., Samsung refrigerators with touch screens on them. You’ll notice that most true luxury built-in brands don’t have a laundry list of gimmick features.

That's so they don't tip forward when a rack loaded with dishes is pulled out. There's a fair bit of forward leverage in that weight distribution.

So I'd say they face the same kind of issues.

I just changed the casters on my 42U rack, without moving (or shutting down) any of the machines. Now that required some deliberateness.

Electrically, you just need to: 1) connect both wires from the old mechanical thermostat to the "Cooling" terminal block (polarity doesn't matter). Or if your model doesn't have separate heat/cool the "relay" and configure settings for cooling mode rather than heating. 2) Tap into hot and neutral wires (going to the light bulb but BEFORE the door switch) and connect that to the STC-1000 power input (polarity doesn't matter).

Then configure the STC-1000, set a temperature to maybe 4C and set the "compressor delay" to at least 4 min, though I'm happy with 10. The default difference of 3C should be fine.

The plastic cutting varies by refrigerator design, but shouldn't be too confusing.

There is a wiring diagram for the STC-1000 in the manual: https://images-na.ssl-images-amazon.com/images/I/71VSFdFfszL...

...and right on the unit: https://wiringandcircuit.blogspot.com/2025/04/temperature-co...

There are videos of it being installed (not a refrigerator retrofit): https://www.youtube.com/watch?v=30TvX1Zz1-Y

...and being configured: https://www.youtube.com/watch?v=TQjicdtDVrQ

We too have a Bosch dishwasher so - like you - we'll see how that goes...