How much energy to heat a room, and heat pump efficiency?

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Discussion Overview

The discussion revolves around the energy requirements for heating a room using a heat pump, specifically focusing on the energy needed to operate a heat pump compressor for a 10 ft. x 10 ft. room. Participants explore variables such as insulation, climate, and alternative methods for driving the compressor.

Discussion Character

  • Exploratory
  • Technical explanation
  • Mathematical reasoning

Main Points Raised

  • One participant suggests that the energy needed is actually power, emphasizing the dependence on insulation and climate conditions.
  • Another participant proposes a rough estimate of 10 W/sq ft for heating in a cooler climate, leading to an input power calculation based on the coefficient of performance (COP) of a heat pump.
  • A participant calculates that for a 10 x 10 room, 1000 watts would be required to maintain a typical temperature, questioning if this could be expressed as 1 kWh per hour.
  • There is clarification regarding the terminology of "watts per hour" versus "watt-hours," with a distinction made between power and energy units.
  • Participants discuss the equivalence of watts and BTUs, noting the common interchange of terms in casual conversation.

Areas of Agreement / Disagreement

Participants express some agreement on the calculations related to power and energy but also demonstrate uncertainty regarding the correct terminology and the implications of different units. The discussion remains unresolved on the exact energy requirements and the best way to express them.

Contextual Notes

The discussion highlights limitations in assumptions about insulation and climate, as well as the potential confusion surrounding the use of energy and power units. There are also unresolved questions about the efficiency of heat pumps under varying conditions.

Who May Find This Useful

This discussion may be of interest to individuals exploring heating solutions, energy efficiency, or those studying thermodynamics and HVAC systems.

ProtoBob
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O.K. this is maybe a large question...

I am trying to find out how much energy it would take to do the work of a heat pump compressor that would be required to heat a... let's say 10 ft. x 10 ft. room of a typical house.

I know there are a lot of variable here...

What I am trying to discern from this, is, if there were an alternate method to drive a heat pump compressor motor, how much energy would be required to do so...

Any thoughts?
 
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You're not looking for energy, you are looking for power. This is very dependent on things like insulation and climate. A good starting guess of required heating for a relatively cool climate (say, the northeastern United States) would be 10 W/sq ft. A decent heat pump has a COP of 2.5 when it is cold outside, so that gives an input power of 4 W/sq ft.
 
If I am understanding correctly, that's 10 watts per sq. ft. so a 10 x 10 room would be
100 sq. ft. requiring 100 * 10 watts, or 1000 watts to maintain a "typical" temperature.

Could this also be stated as 1000 watts per hour or 1kwh to maintain room temperature?

would this also be equivalent to 3413 btu per hour?

Thanks! :)
 
ProtoBob said:
If I am understanding correctly, that's 10 watts per sq. ft. so a 10 x 10 room would be
100 sq. ft. requiring 100 * 10 watts, or 1000 watts to maintain a "typical" temperature.
Could this also be stated as 1000 watts per hour or 1kwh to maintain room temperature? [/quote] There is no such thing as "watts per hour". There is watts for an hour, which is watt-hours (or 1000 watt-hours = 1 kWh). Watts is already a rate.
would this also be equivalent to 3413 btu per hour?
Yes, though note that people do a kind of short-hand and often interchange "BTU" and "BTUH". BTU is technically the rate (power, like kW) and BTUH is the energy (like kWh).
 

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