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I'm new to this area and know very little about electrons and how electrical components work. I'm always curious about Inverter/UPS usage.

I'm from India and we have a inverter at home. It is attached with two batteries which will supply the power for my home for 8 hours (TV, 4 ceiling fans, 4 lights). When there is interruption in power supply I drain out the inverter completely and when power comes back it gets charged fully in 2 hours.

I was always thinking that if it can charge up fully in 2 hours and supply power for 8 hours then I can save electricity for 6 hours which I'm paying to supplier by disconnecting power supply after my inverter charge up completely.

I know this is silly thinking but I want to have some explanation from experts saying that my thinking is incorrect, because if that happens then everyone in this world can save lot of power.

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Do you pay per hour that the electricity is turned on, or do you pay per unit of energy that you use? :) – endolith Apr 5 '11 at 14:23

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Electricity isn't simply on or off... you're missing the quantity of electricity which is measured in Amperes (Amps for short).

So, while your UPS is charging, it's using lots of electricity to charge your UPS storing a large amount of power as well as the relativity small quantity of electricity powering your house.

When the power is switched off, your UPS is just providing the relativity small quantity of electricity for your home appliances.

So, in the space of time it takes to charge your UPS, your electric company will charge you the cost of 8 hours worth of electricity, plus 2 hours of normal use, plus a tiny bit extra for the inefficiency of your UPS.

If you do this, it will likely cost slightly more than you are paying now, due to the UPS inefficiencies.

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Thanks for clarifying me. – JPReddy Apr 5 '11 at 18:22
The only way I could think that you could do this to save money is if the electric company charged different rates depending on current demand, and you charged the UPS during the cheapest time (low demand hours) and switched to it during peak demand hours. – Jared Harley Apr 6 '11 at 10:38

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