Back in the old days, fridges didn’t run nearly as much as they do today. They ran around once an hour. I had an old one plugged in in the garage with nothing else running and it cost about a buck for the electricity to run it. The new frost free fridges are not very efficient as they say they are. They are better than they were back in the later sixties through eighties, but are by far not as efficient as the old ones from the fifties. They had thick walls, were super quite, and did not use much juice. No heating coils to keep them frost free by warming and cooling the air to pull out moisture as it blows through the unit. The efficiency specs of fridges doesn’t include the self defrost cycle to judge it. Some government programs actually require the true efficiency but the consumer specs we see on the tag do not do that, they exclude the warming cycle effect. We live in a world full of deceit, scientific evidence is constantly being corrupted to make it appear different than it is.
My refrigerator installer suggested empty paper bags would improve efficiency by welling the cold air inside instead of letting it spill out onto the floor.
A buck per day, per month, per year, or what? An average modern refrigerator uses about 30 kWh per month, which at average US electricity rates would cost about $4 per month. But electric rates vary greatly in different areas; depending on where you live it could cost from $2.50 (Idaho) to $10 (Hawai’i). Also, if you live in a cold climate and your garage was unheated, any refrigerator would use less electricity during the cold months when the ambient air is cold.
The error the necromancer made is he forgot that this problem is governed by energy losses.
The full fridge did need more heat extracted (and thus energy consumed) to cool down. But once it’s steady state, the only cost in energy is needed to pump the heat that leaks in through the fridge’s insulation. If the fridge were using the best available vacuum insulation and were welded shut, it could stay cold for years without needing energy at all.
So the only difference when you consider losses is the air volume of cold air that is lost when someone opens the door. And since the full fridge has less air volume that can flow out, it loses less energy when you open the door.
The fact that the cold items already in the fridge help the new thing you added cool down faster is totally irrelevant.
My dad fills the fridge up before he goes away on holidays, because ‘a full fridge is more efficient’. I came over to visit once when he was away, and the fridge was full of rolls of toilet paper. I’m hoping this thread will decide one way or the other whether or not that’s actually helpful so I can let him know.
In the real world … just not opening the door as often as what five teen-age kids would think is okay is probably the best money-saving advice … because a kW-hr per day is very reasonable just only opening the thing when absolutely necessary …
It will not help in the slightest because a closed fridge, empty or full, has the same heat losses through the sides. A fuller fridge only helps if someone is frequently opening it. And I’m not sure even that matters much, by the estimate above, it’s only about 5% more energy consumption, full vs empty, if someone opens it every hour.
Irrelevant to the efficiency, but not to the effectiveness. A full fridge works better.
A full fridge (or freezer) also holds its temp better if you have a brief power outage, but of course, if that turns into a long power outage, you lose more food. I have lots of brief power outages, and like to keep both compartments full.
Beer is an amazingly high heat capacity … nearly as high as water …
Not necessarily, depending on what you’re putting in to fill it. A lot of things in my fridge don’t actually need refrigeration at all, and are only there because it’s a convenient place to put them and there’s room, and a lot of other things are more appealing cold, but won’t actually go bad if they warm up. If I start with a fridge that’s mostly empty (containing just the things like milk that need it), and add (for instance) a bunch of cans of pop, I have increased the thermal ballast of the fridge, but I am not risking any more food.