Suppose heating is out and the house has to be in 45 Fahrenheit temps indoors for a couple of days until the technician comes - how long can laptops and modems/routers survive if turned off? What if turned on?
Fine in all cases indefinitely. You should be able to look up the temperature restrictions for the specific equipment you have.
Would it be better to leave them turned on so that they generate some heat of their own?
For example my old laptop says the battery should not be exposed to temperatures about 149 degrees Fahrenheit and if the battery is below 32 degrees Fahrenheit the computer won’t start up.
Computers aren’t human so they don’t need to be in temperature ranges humans are comfortable at.
While electronics generally work best (or even only, for many domestic electronics) at temperatures within the 0-40ºC range, the temp you’re giving is within that range and the temperatures at which the equipment would be damaged from just being in it are muuuuuuuch more extreme. If you’ll allow me a somewhat silly example, your ice tray works best at temps in the -10 to 0ºC range but it won’t be damaged by being in a drawer at 25ºC, much less by being kept dry and in a drawer at -1ºC (which is actually within its working range).
The only risk is when cold electronics are exposed to warm, humid air. E.g. when you bring a laptop indoors after it sat outside in the cold. Then you get condensation forming inside, which can cause a short circuit.
But gradually warming up the whole house with the computer in it should be fine.
The other limitation is that batteries don’t work well while they’re cool. Cooling a battery down won’t damage it (and in fact, might increase its shelf life); you just have to wait for it to warm up before using it.
Other than that and issues with condensation, electronic devices will actually work better the colder they get, down to nearly absolute zero.
Yep- condensation and battery issues due to cold are the only things you might have to worry about. Otherwise, they’ll actually tend to work better at colder ambient temps- their cooling systems work better!
Moisture is definitely not good for electronics. But pure water (as from condensation) has poor conductivity, so short circuits should not be a big concern.
ISTM that asking how long an electronic device can withstand a temperature of 45F is roughly like asking how long a human can “withstand” a temperature of 72F.
Pretty much identical question 13 years ago:
I think there was another one in the last year or so but I couldn’t find it.
That would be true if all the surfaces inside the electronics were perfectly clean. In reality, all surfaces have contaminants, some of which will dissolve into the dew and cause it to be impure.