About

Thermal dynamics and electrical engineering often intersect when sizing heating ventilation and air conditioning (HVAC) systems. While electrical input is measured in Watts, the thermal output or cooling capacity is frequently discussed in kilocalories per hour (kcal/hr), particularly in older metric systems or specific nutritional science applications involving metabolic chambers. Accurate conversion ensures that heating elements meet the thermal load requirements of a specific volume.

This tool bridges the gap between electrical ratings and thermal capacity. The conversion relies on the definition where one electrical Watt equates to approximately 0.86 kilocalories per hour. Engineers sizing radiators or metabolic researchers analyzing energy expenditure use this relationship to correlate power consumption with heat generation or loss. The calculation assumes a direct conversion of energy without efficiency losses unless otherwise factored into the input.

Formulas

The conversion from electrical power to thermal energy rate is defined by the following constant:

P_kcal/hr ≈ P_W × 0.859845

Where P_W represents the power in Watts and P_kcal/hr is the resulting thermal energy per hour.

Reference Data

Power (Watts)	Thermal Rate (kcal/hr)	Typical Application
10 W	8.60 kcal/hr	Small PCB Heater
60 W	51.59 kcal/hr	Incandescent Bulb Heat
100 W	85.98 kcal/hr	Human Basal Metabolism
500 W	429.92 kcal/hr	Personal Space Heater
1000 W	859.85 kcal/hr	Standard Electric Heater
1500 W	1,289.77 kcal/hr	Large Room Heater
2000 W	1,719.69 kcal/hr	Immersion Heater
3500 W	3,009.46 kcal/hr	Central AC Unit (Small)
5000 W	4,299.23 kcal/hr	Server Rack Cooling Load
10000 W	8,598.45 kcal/hr	Industrial HVAC Unit

Frequently Asked Questions

This factor derives from the definition of energy units. One Watt is one Joule per second. One calorie is approximately 4.184 Joules. Therefore, 1 Watt = 1 J/s = 3600 J/hr. Dividing 3600 by 4184 (J per kcal) yields approximately 0.859845.

Yes. The "kcal" used in physics and engineering is the kilocalorie, which is identical to the "Calorie" (capital C) found on nutrition labels. Both represent the energy required to raise the temperature of one kilogram of water by one degree Celsius.

Yes. While air conditioners are often rated in BTUs or Tons, kcal/hr is a valid unit for cooling capacity (rate of heat removal). The conversion math remains the same regardless of whether energy is added (heating) or removed (cooling).

No. This tool converts the raw power unit. For a heater, efficiency is often near 100% (all electrical energy becomes heat). For motors or compressors, you must apply the device's specific efficiency coefficient before converting.