# How much burning coal does my electrical heater use? **URL:** \ **Category:** Factual Questions\ **Created:** [February 21, 2013, 3:02am UTC](https://boards.straightdope.com/t/how-much-burning-coal-does-my-electrical-heater-use/650938 "2013-02-21T03:02:37Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Hank\_Beecher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hank_beecher/32/7275_2.png) [@Hank\_Beecher](https://boards.straightdope.com/u/Hank_Beecher)\ **Post date:** [February 21, 2013, 3:02am UTC](https://boards.straightdope.com/t/how-much-burning-coal-does-my-electrical-heater-use/650938/1 "2013-02-21T03:02:37Z")
I have one of these little ceramic heaters with a fan that are sold everywhere. It says it is 1500 watts, it puts out a decent amount of heat. How much heat is the coal that is generating the electricity that is powering it giving off inside the power plant? (Simplifying things and assuming all of the power for it comes form the nearest source, which is a coal plant a few miles away) In other words, the system composed of the power plant plus the electrical grid plus this little heater turns the heat of the coal in the plant to electricity and back to heat in my house, roughly how efficient is this system as a whole? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [February 21, 2013, 3:49am UTC](https://boards.straightdope.com/t/how-much-burning-coal-does-my-electrical-heater-use/650938/2 "2013-02-21T03:49:44Z")
According to Wikipedia > [@](#): > > Typical thermal efficiency for utility-scale electrical generators is around 33% for coal and oil-fired plants Combine this with > [@](#): > > Transmission and distribution losses in the USA were estimated at 6.6% in 1997[10] and 6.5% in 2007 And you get an overall efficiency of around 26%. So, for each BTU that your heater generates (electrical heaters are 100% efficient), you need to burn around 4 BTUs worth of coal. ---
**Author:** ![lisiate](https://avatars.discourse-cdn.com/v4/letter/l/f05b48/32.png) [@lisiate](https://boards.straightdope.com/u/lisiate)\ **Post date:** [February 21, 2013, 4:58am UTC](https://boards.straightdope.com/t/how-much-burning-coal-does-my-electrical-heater-use/650938/3 "2013-02-21T04:58:05Z")
Quoth [wiki](http://en.wikipedia.org/wiki/Coal) > [@](#): > > The energy density of coal, i.e. its heating value, is roughly 24 megajoules per kilogram (approximately 6.7 kilowatt-hours per kg). So running with **beowulff’s** figure of 26% for the system’s energy efficiency a kilo of coal will power your heater on full for 1.61 hours (1 hour and 36 minutes). ---
**Author:** ![YamatoTwinkie](https://avatars.discourse-cdn.com/v4/letter/y/cc9497/32.png) [@YamatoTwinkie](https://boards.straightdope.com/u/YamatoTwinkie)\ **Post date:** [February 21, 2013, 1:39pm UTC](https://boards.straightdope.com/t/how-much-burning-coal-does-my-electrical-heater-use/650938/4 "2013-02-21T13:39:28Z")
> [@beowulff](#): > > And you get an overall efficiency of around 26%. Nitpick: efficiencies are not additive. 33%\*(1-0.066) = 31% ---
**Author:** ![BubbaDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bubbadog/32/333_2.png) [@BubbaDog](https://boards.straightdope.com/u/BubbaDog)\ **Post date:** [February 21, 2013, 2:40pm UTC](https://boards.straightdope.com/t/how-much-burning-coal-does-my-electrical-heater-use/650938/5 "2013-02-21T14:40:53Z")
And just to help make this a little more confusing it should be noted that the impact of your heater to the utility’s coal supply is probably around 80% of the number calculated based on the plants efficiency. Why? Because the calculations are based on the _average_ efficiency of the plant. But your usage represents an _incremental_ load to the plant and the incremental difference of producing that load is usually around 80%\* of the average. This is similar to the economics of cruise ships. It might cost the cruise ship $500 per passenger to provide the service but the incremental cost of adding 1 passenger to the ships services is $250 so it makes sense economically to fill any available space with customers who will pay any amount over that. So if you decide to turn off your heater you’re only saving 80% of the average coal. And if you plug another heater in to the system you are only increasing the coal load by 80% of the estimate. Here are the average and incremental estimates based on [this](http://www.eia.gov/tools/faqs/faq.cfm?id=667&t=3) site’s estimate of 1.07 lb/kwh **Average burn** KWH load X pounds/KWH X Loss inverse 1.5 X 1.07 X (1 -.066) = 1.499 Lb **Incremental burn** KWH load X (pounds/KWH X incremental factor) X Loss inverse 1.5 X (1.07 X 0.8) X (1 -.066) = 1.199 Lb - Heat rates both average and incremental and cost are tricky numbers and vary considerably depending on the load level of the generator. I chose 80% because it is typical of the incremental heat rate of a unit that is sitting in its “sweet spot”; its most efficient output point ---
**Author:** ![Hank\_Beecher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hank_beecher/32/7275_2.png) [@Hank\_Beecher](https://boards.straightdope.com/u/Hank_Beecher)\ **Post date:** [February 21, 2013, 8:55pm UTC](https://boards.straightdope.com/t/how-much-burning-coal-does-my-electrical-heater-use/650938/6 "2013-02-21T20:55:06Z")
Thank You. Seems very efficient. Even if everyone was able to burn the coal directly for heat it would have to be distributed, which would take energy. I was expecting the coal to electric heater system to be far less efficient, what with all the little wires the energy goes through, and the losses due to changing from heat to kinetic to electric and back to heat. ---
**Author:** ![lisiate](https://avatars.discourse-cdn.com/v4/letter/l/f05b48/32.png) [@lisiate](https://boards.straightdope.com/u/lisiate)\ **Post date:** [February 22, 2013, 1:30am UTC](https://boards.straightdope.com/t/how-much-burning-coal-does-my-electrical-heater-use/650938/7 "2013-02-22T01:30:36Z")
Don’t forget your average home coal fire would likely to be pretty inefficient and almost certainly lead to smog problems if that were the main method of heating in your town. ---
**Author:** ![VOW](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/vow/32/3043_2.png) [@VOW](https://boards.straightdope.com/u/VOW)\ **Post date:** [February 22, 2013, 2:34am UTC](https://boards.straightdope.com/t/how-much-burning-coal-does-my-electrical-heater-use/650938/8 "2013-02-22T02:34:26Z")
Back when the stegosaurus still roamed the Earth (actually, the early 80s), we lived in a place that was 100% electric. When I’d drive to work, I’d see the enormous warehouses with coal that were destined for the electricity generating plants, and I wondered about the efficiency. I seem to remember reading about the topic in the local paper: I was interested, because I’d never lived in a place so dependent on electricity. IIRC, the efficiency figure quoted then was along the order of 5%. ~VOW