Electricity Myths

Does it take more energy to turn on a light than to leave it on?

No. There's no power surge when you turn on a light. Turning the light off ALWAYS saves electricity, even if it's for just a second. (more on lighting...)

Does it take more energy to turn on a computer than to leave it on?

No. There's no meaningful power surge when you turn on a computer. Turning the computer off ALWAYS saves electricity. Of course, you can also use the power saver feature. (more on computers...)

Is there ANY consumer device that uses more energy when you turn it on than when it's already on?

No, not in practical terms.

I don't believe you. Everyone says there's a surge when you turn on computers and stuff.

There's a surge but it's so tiny you can't easily measure it. That's because it happens for only a fraction of a second, and the surge itself is modest. It's certainly not costing you any extra money, not even a penny. So there's no surge in practical terms. As far as you're concerned there's no surge at all.

Think of it this way: If a device used twice as much power as normal for one full second when you turned it on, that would mean that it cost you one whole extra second of electricity. Big deal. That's a fraction of a fraction of a fraction of a penny. And in fact, the surge doesn't really last for a whole second, it lasts for only a fraction of a second, and the surge isn't close to twice as much power as normal, it's much less. Bottom line: Surge is so incredibly insignificant it's really like there was no surge at all, for all intents and purposes. There is never a penalty for turning on a household device.

Does it take more energy to cool a house in which the AC has been off all day, than to keep the AC running at, say, 85 degrees during the day?

No. Cooling a hot house down at the end of the day always takes less energy than leaving the AC running all day, even if it's running on a high setting. (more on cooling...)

Does a 240V device use more electricity than the same device designed to run off 120V?

No. The electric company charges you for watt-hours, not volts, and the wattage is the same. To figure volts you use the fomula V x Amps = Watts. A device that uses twice as many volts will use half as many amps, so the wattage will be the same -- and so will the cost.

Electricity Facts

I heard that an electrical wiring problem can lead to electricity "leaking" out of the wires and into the abyss, causing a person to pay for electricity that they don't use.

Yes, this is a possible.  Note that on an earlier version of this page, I mistakenly listed this one as a Myth, but an electrician corrected me.  When the wiring isn't connected correctly, it is indeed possible for electricity to "leak".  The electrician who contacted me had a customer with a $15/mo. leak due to faulty wiring.  On another page I have detailed instructions on how to check for this kind of electricity leak.

Besides mis-wiring, you could also have undersized wiring, where the wiring is too thin to handle the load being driven.  When that happens the wiring heats up.  The extra heat generated represents wasted energy, but more importantly, the extra heat can cause a fire which can burn your house down.  If you have a modern home which had an electrical inspection when it was built then it's unlikely that your wiring is inadequate.  But if you have an older home or your wiring was never inspected when installed, it's possible that your wiring isn't sufficient for what you're running through it.  Unfortunately this isn't the kind of thing you can easily test yourself.  That's a job for a competent electrician.