BTU/hr stands for British Thermal Units per hour, a unit of heat flow commonly used in HVAC, refrigeration, and industrial heating. One BTU is the amount of energy needed to raise the temperature of one pound of water by one degree Fahrenheit. When expressed per hour, it quantifies the rate at which thermal energy is transferred.
Understanding Horsepower (Electric) (hp)
Horsepower (electric) is a unit of mechanical power that originated from the output of draft horses. In the electric context, 1 hp equals 746 watts. It is frequently used to rate electric motors, compressors, and other powered equipment.
Why convert BTU/hr to hp (electric)?
Many engineers need to size electric motors that will move or compress a certain amount of heat. Converting BTU/hr to hp provides a direct link between the thermal load and the motor power required, simplifying equipment selection and energy‑efficiency calculations.
HVAC system design – matching heat‑transfer rates to motor capacity.
Industrial process heating – ensuring motors can sustain required heat flow.
Energy audits – translating thermal losses into electric power demand.
The conversion factor is:
\(1\ \text{BTU/hr}=0.0003928565683646113\ \text{hp (electric)}\).
This factor is derived from the relationship \(1\ \text{hp}=746\ \text{W}\) and \(1\ \text{BTU}=1055.06\ \text{J}\).
BTU per hour to Horsepower (Electric) Conversion Reference Table
BTU per hour (BTU/hr)
Horsepower (Electric) (hp)
0.1
3.9286e-05
0.5
1.9643e-04
1.0
3.9286e-04
2.0
7.8571e-04
5.0
0.002
10.0
0.0039
20.0
0.0079
50.0
0.0196
100.0
0.0393
500.0
0.1964
1000.0
0.3929
Step‑by‑Step Conversion Example
Convert 10 BTU/hr to horsepower (electric).
Write down the known value and the conversion factor.
\[10\ \text{BTU/hr}\times0.0003928565683646113\ \frac{\text{hp}}{\text{BTU/hr}}\]
Multiply the numbers.
\[10\times0.0003928565683646113 = 0.003928565683646113\ \text{hp}\]
Round to a sensible number of significant figures (typically 4).
\[\approx 0.00393\ \text{hp}\]
Therefore, 10 BTU/hr is approximately 0.00393 hp (electric).
The factor 0.0003928565683646113 is exact based on the definitions 1 hp = 746 W and 1 BTU = 1055.06 J. In practice, rounding to 0.000393 or 0.00039 is acceptable for most engineering calculations, introducing less than 0.1 % error.
Electric horsepower is used when the power source is an electric motor, which is the case for most HVAC compressors, fans, and pumps. Mechanical horsepower applies to engines or systems driven by combustion or other non‑electric means. Use the electric hp conversion when sizing or comparing electric motor ratings.
"On fait la science avec des faits, comme on fait une maison avec des pierres ; mais une accumulation de faits n'est pas plus une science qu'un tas de pierres n'est une maison." "Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house." — Henri Poincaré (French Mathematician, Theoretical Physicist & Mining Engineer)