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Watts & BTUs

MKbTQnXQKU | Posted in Energy Efficiency and Durability on

I’m looking at 2 types of electric towel warmers in a bathroom remodel and am confused at the difference in heat output with similar watts.

One model ( has a 300w element, is oil-filled and has 2267 BTU output. The other is filled with glycol/water says 240watts and 818 BTU. (

Do these numbers mean the first is more energy efficient? Or could there be a mistake in the numbers? And is 2267 BTUs in the first model high enough to be noticeable in helping to heat the bathroom rather than just the towels (it’s about 80sq ft)?

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  1. user-729621 | | #1

    I think you can ignore the BTU rating, electric heaters are essentially 100% efficient, and the correct british output should be in BTU/hr. For some reason Americans think in the metric watts when it comes to electricity, so just stick with it and ignore the rest.

  2. jklingel | | #2

    1 watt = 3.4 btu. The first btu is an error. Will it help heat the room? Depends on your heat loss, which could be anything from 2 to 30 or more btu/hr/sf.

  3. KHWillets | | #3

    The Google calculator actually gets this unit conversion:

    300 watts in btu/hour = 1023.64
    240 watts in btu/hour = 818.9
    240 watts = 1.49796234e18 electron volts / millisecond (you can type in just about any units)

  4. davidmeiland | | #4

    I didn't look at either link, but there's no way a 300w/hr heater is going to produce 2267 BTU/hr. In a relatively tight house I would expect them both to produce noticeable heat in a 80sf bathroom. What are electric rates? Does the house have central heat?

  5. MKbTQnXQKU | | #5

    Sounds like the watts-BTU ought to be a simple conversion x3.4 so the first link must be a mistake? I looked at other models in that website & they also claimed very high BTUs with small watts (not a 3.4: 1 ratio). Yes, the house is centrally heated (electric) & we are in a cold zone (mid New Hampshire) - I had not expected the Amba model to make much impact on the room temp (they're careful not to mislead on heat expectations), and if the heat output of the other model was really 3 times higher might have chosen that one. But if it's a mistake I'd like to know that before I buy!!

  6. GBA Editor
    Martin Holladay | | #6

    It's impossible to convert watts to BTUs. Watt is a measure of power; BTU is a measure of energy.

    However, it is possible to convert watts into BTU/hour: 1 watt = 3.4129 BTU/hour.

    If you want to convert BTU into a unit in the metric system, choose watt-hours or (more conventionally) kilowatt-hours: 1 kWh = 3,412.9 BTU.

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