How much is my space heater costing me per hour?

February 8, 2012 6:42 AM

Can a math / electrician whiz help me figure out how much my little space heater is costing me to run? The heater is listed as 120V 60Hz 1500W, and I run it on its highest setting for about 8 hours a day. According to my last utility bill, my electric was $118.64 for 1536 kWh, or $0.077239583 per kWh. So how much is this little heater costing me to run per hour?
posted by bjork24 to Home & Garden (13 answers total)

Best answer: Cost per hour = Cost of 1kW x no. of kW

= 0.077 x 1.5

= 11.5 cents per hour.
posted by le morte de bea arthur at 6:45 AM on February 8, 2012 [1 favorite]

(sorry, that's 'Cost of 1kWh')
posted by le morte de bea arthur at 6:46 AM on February 8, 2012

Not enough info to actually know.

1500W is 1.5kW. If it actually used that much power all the time then it would consume 1.5kWh every hour. But in reality it probably doesn't use 1500W even on full blast, and it cycles on and off according to its thermostat. So, you can't calculate the power use from these numbers. You need something like a kill-a-watt device to measure the power consumption directly.
posted by jon1270 at 6:48 AM on February 8, 2012

Response by poster: Thank you, le morte! That formula was more straight forward than I would've guessed.
posted by bjork24 at 6:50 AM on February 8, 2012

I agree wth jon1270, by the way - my answer is an upper limit, assuming the heater is constantly on, and not cycling due to the thermostat.

It's possible that the heat is on all the time, but that's only likely if the thermostat is set high, and the room is very draughty or too big for the heater.
posted by le morte de bea arthur at 6:55 AM on February 8, 2012

If you really want to know, get a Kill A Watt. It measures the actual power draw of whatever's plugged into it, so it avoids the issues pointed out by jon1270.
posted by The Michael The at 6:55 AM on February 8, 2012 [1 favorite]

Also, are you taking into account other factors such as electricity for lighting, electronics, appliances, etc? In your home in that $118?
posted by HeyAllie at 6:58 AM on February 8, 2012

le morte de bea arthur's result is a good upper limit, and is probably good enough for government work. If you want to be more precise, though, you'd also need to subtract from the $118.64 on your electric bill any fixed costs ("connection fees" and the like) that are independent of the amount of energy you consume to determine the additional money you spend per kilowatt-hour. I doubt this'll change things by more than 10%, but you never know.
posted by Johnny Assay at 7:08 AM on February 8, 2012

Look more closely at your bill. It'll actually tell you what your rate is, and you can't just divide the total bill by the kWh consumed. As Johnny Assay indicates, there are fixed fees and taxes that go on top of your actual consumption, and it's entirely possible that you are charged different rates at different times of day.

I, for example, pay about $0.027/kWh from 9PM-6AM and on weekends, but about $0.125/kWh from 6AM-9PM during the week. My bill shows not only how much power I used total, but how much power I used when.
posted by valkyryn at 7:13 AM on February 8, 2012

You don't necessarily need a kill-a-watt (though they are awesome) to figure the actual draw of a given device. You can get a baseline draw from your house if you can access your electrical meter. Find the baseline usage, go turn on heater, go back to meter, monitor for a bit, subtract, done.

This is only if you're really, really interested of course, but it seems you might be.
posted by RolandOfEld at 7:19 AM on February 8, 2012

My local library has a Kill-a-Watt available for checkout - see if yours does.
posted by unixrat at 7:23 AM on February 8, 2012 [3 favorites]

If, on the other hand, all you need is the upper limit, lmdba has your answer. You are all set tell your roommates/parents/spouse or other bean plating bill watcher, "Look, this only costs 11 cents an hour, so get off my case." or 0.88 per day. Or in other words...wait....damn ....going to app store....downloading calculator...tap tap tap.
Holy Moly. That little heater is costing you $26 a month!!!! Put on a sweater why doncha?
posted by SLC Mom at 8:17 AM on February 8, 2012 [1 favorite]

My utility bills in tiers based on a "baseline". Usage that is 101-130% over the home's allocated baseline is charged a bit higher rate per killowatt hour. The rate for 130-200% is almost 3x that for baseline. If your util isn't billing flat rate, your question is harder to answer.
posted by nakedcodemonkey at 8:43 PM on February 8, 2012