> not a fair comparison. Most likely the door of the old one was not sealing well, hence the continuous running and frost buildup

That's an expected cost of old fridges, so I don't know that it's unfair. A major reason old machines are less efficient is accumulated defects (people too!). If I said comparing a new car's fuel efficiency to my old one was unfair, because my old one has a lot of problems, you might say that's very fair.

it depends on why and exact purpose of said comparison.

If the comparison is meant to show the drop in efficiency as part of age and usage, then yes.

However, if you wanted to _only_ compare design upgrades, you don't want wear and tear to confound the results.

Yeah, I too am unsure why anyone would think comparing a 30 year old fridge in the worst condition for testing is somehow a useful comparison in any meaningful way.

Is it really normal to want an off the line 2025 Tesla and a 1985 Lincoln Towncar with 376k miles on its second motor with a missing cat that was stolen last month for a quarter mile comparison?

I would say it would be fair to compare a new fridge with a 30 year old fridge in good working condition. And a fridge that has one of its two compressors running all the time is obviously not in good working condition.

You can restore the old fridge

Unless you have a fridge assembler from that same factory with the same materials also on ice, modern tools, techniques, and methods would make this an exercise in futility with regards to an apples-to-apples like-new comparison. We don’t even use CFCs anymore, for one.

You're sidestepping the point with valid re-herrings. If the old refrigerator's compressor hardware were left unchanged, possibly repairing the thermostat or contactor causing the malfunction, cleaning the air exchanges, and replacing the seal: based on the OPs own usage chart would have consumed equal if not less energy noting it was a dual compressor model.

Are we making an accurate comparison considering the internal cooled space of older fridges versus newer ones? Many older refrigerators were smaller, so the same power consumption for a smaller internal volume isn’t telling the whole story, but I digress.

>If I said comparing a new car's fuel efficiency to my old one was unfair, because my old one has a lot of problems, you might say that's very fair.

If it's a simple as not driving the old one with punctured tires and replacing those first to get a dramatically different comparison then no i'd say it's unfair.

Replacing a broken thermostat or fixing a rubber seal isn't a huge thing. Why else make the comparison? Who cares about this broken one?

It depends what you are comparing:

If you're comparing technologies, then you want to eliminate the variable of condition.

If you are comparing the values or efficiency of actual old fridges and new fridges - for example, to decide whether to replace the old ones - then it's false data to assume the old fridges are in the same condition as new ones.

I am not even sure there's anything wrong with the old fridge.

Ice buildup on the cooling element is normal in old fridges - you need to melt them down occasionally - we used to do this once a year, as ice insulates the element from the inside of the fridge and prevents it from working properly.

I thought this was common knowledge.

It's also possible that the thermostat inside was broken. For a 30 year old appliance it was probably impossible to find a replacement, but if you can replace it and it doesn't cost as much as a new fridge, that would fix it.

I'm 99% confident that freezer thermostats are cheap and generic components that haven't changed much in the past decades, however, finding and installing it is a whole other matter.

> I have a late 30s Frigidaire that I restored a few years ago

Did I read that right with 30s, as in 1930s?

Not sure of the exact year, but it should be around 1936-1940.

Honestly given how many compromises there are in refrigerants sold now, it wouldn't surprise me with new seals and a good compressor motor if the old stuff did better.

For sure, the base tech in a freezer hasn't changed in the past 50 years. Different refrigerant maybe (CFCs are bad mkay), maybe different insulation material, but the rest has just been adding smart features and buttons that really are secondary to the main function of a freezer.

And, sadly, moving to cheaper, thinner materials with a lesser lifespan.

I’ve personally seen it in the appliances I’ve bought where I’ll run an appliance for 15-20 years, but the same model. They will largely look identical but when disassembled, the newer model trades metal part for plastic or the material is thinner.