I have recently been measuring the power consumed by a 1969 and a 2008
fridge freezer of nearly equal size, about 14 c ft for each unit. I
used two of those power measuring meters that are available these
days.

The 1969 unit uses about 10% more power than the newer unit.

This isn't saving a lot of money since the new unit's power
consumption is approximately equal to a 40W bulb running continuously.
(Btw this is typical a power consumption of modern refrigerators.)

At 18 c Kw/Hr a mere 4 W saving per hour isn't ever going to amount to
much money.

Refrigerators/freezers typically use less than a 60W bulb running
continuously.

At 18 cents/KwHr this costs $ (60/1000) X 24 X365 X 0.18 pa

= $94.60 pa

Here in Australia refrigerators and freezers typically cost $900 or so
new. Even if your new refrigerator/freezer used zero power compared to
the old rerfigerator at $94.60 pa it would take about 10 years to pay
for the new refrigerator.

In practice, as measured on my actual 1969/2008 units and with a mere
10% _measured_ difference in efficiency, it would be more like 100
years payback time.

Fix your 1950's unit and enjoy!

I'd suggest power savings with new units would be minimal.

Otoh convincing folk to buy new units means a lot of $$$$$ to
manufacturers.

Ross