It looks like modern refrigerators are considered about 3x as efficient as pre-70s refrigerators, so let's say that a straight swap of a size-equivalent refrigerator of average efficiency will cost 100kWh/year.
...and that's where you're wrong. These are the most efficient as of 2020:
The top of that list is a 5.1cft model that uses 186kWh/year. The next one is also roughly the same size and uses 202kWh/year, followed by an 8.8cft that uses 294kWh/year. 100kWh/year is, frankly speaking, impossible. Mine has 9cft.
That "calculator" is being very deceptive by grouping everything "before 1980" together. The 60s and 70s models are certainly far more power-hungry because they made them bigger and with thinner insulation (more interior space) and things like defrost heaters, but the ones before that are not.
This DOE paper talks in detail about the changes that improved efficiency
...and none of the energy usage figures they quote are anywhere near the 300kWh/year range. A look at the real numbers shows just how efficient these early models are.
In EU you can buy a A+++ fridge, that used less than 100kWh/year. Granted, I have not put a meter on mine, so I'd have to take the 2010/30/EC specification at face value.
75kWh/year is for the "cooler" only, which doesn't go below freezing. Ice takes a huge amount of energy to make, so that isn't surprising. I'm not sure I can even set my vintage fridge to not freeze, but it would probably consume in that ballpark too if I never let the evaporator go below 4C or so. The above link shows the companion freezer, which does, uses a 237kWh/year --- pretty good, but then the two together use a far more realistic 312kWh/year.
If you have both, I suspect that they have significantly more storage than your vintage fridge?
In any case, if you buy a A+++ freezer they "only" use around 200kWh/year. This is mostly due to better insulation, and is in general an environmental and economical benefit to buy if your freezer is old.
Okay :) It sounds like you have sufficient information to make an informed decision.
The only takeaway for me is that a fridge upgrade has to be at least 50 kWh/year more efficient, or it's more likely than not a complete waste of carbon.
...and that's where you're wrong. These are the most efficient as of 2020:
https://www.energystar.gov/most-efficient/me-certified-refri...
The top of that list is a 5.1cft model that uses 186kWh/year. The next one is also roughly the same size and uses 202kWh/year, followed by an 8.8cft that uses 294kWh/year. 100kWh/year is, frankly speaking, impossible. Mine has 9cft.
That "calculator" is being very deceptive by grouping everything "before 1980" together. The 60s and 70s models are certainly far more power-hungry because they made them bigger and with thinner insulation (more interior space) and things like defrost heaters, but the ones before that are not.
This DOE paper talks in detail about the changes that improved efficiency
...and none of the energy usage figures they quote are anywhere near the 300kWh/year range. A look at the real numbers shows just how efficient these early models are.