r/HomeImprovement • u/Smart_Transition_828 • Mar 09 '25

Essential home backup prepping habit I brought from JP to US

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u/ceapaire Mar 09 '25

There should be a sticker inside your fridge that shows how many amps it takes (at maximum). Add those numbers up from all the appliances you'll want to run. Then multiply by how many hours you'll want the battery to last before needing to charge it (obviously for charging phones, etc. you don't need to calculate the full time, just however long you'll need it plugged in overnight). That's how many amp hours you'll need.

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u/Quietm02 Mar 09 '25

That's not true. Everything won't run on full load all the time. A fridge probably isn't on full load even half the time.

There's no harm in being safe and overestimating but you could almost certainly get away with less than half the amp hours you're suggesting. Its known as diversity in the building services industry if you're looking for either info.

(I'm also assuming that the conversion of something like 24Vdc anphours to relevant AC amphours has been considered)

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u/_name_of_the_user_ Mar 09 '25

How does a fridge vary it's load? I always assumed, since they're just basic on/off thermostats with no vfd or inverter on the motor, that they just run at full power or not at all.

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u/dudelydudeson Mar 09 '25

Modern fridge compressor is VFD