My new fridge says it costs $43/year to run. Call it T$
What test conditions lead to that number?

If I let it run and never open the door, it will cost me X$ to run.

So, the annual cost of opening the door is Y$ = T$ - X$.

What's the magnitude of Y$? And what opening rate does it assume?

If it's a significant percentage of the total cost, it might make
sense to address the opening problem.

95% of my accesses are for stuff stored on the door.
The inside is mostly empty and rarely accessed.
Maybe curtain the inside of the box?
OR fill the empty space with empty boxes so less cold
air spills out when the door opens.
It's the same concept
as putting open-topped vessels in your toilet tank to reduce
the water/flush.

Sounds like it's probably way into diminishing returns, but
every little bit helps save the planet.

Any idea the ratio of Y$ to T$?

Thanks, mike