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The SI unit of power for heating and cooling systems is the watt. Btu per hour (Btu/h) is sometimes used in North America and the United Kingdom - the latter for air conditioning mainly, though "Btu/h" is sometimes abbreviated to just "Btu". [18] MBH—thousands of Btu per hour—is also common. [19] 1 W is approximately 3.412142 Btu/h [20]
Although the concept of U-value (or U-factor) is universal, U-values can be expressed in different units. In most countries, U-value is expressed in SI units, as watts per square metre-kelvin: W/(m 2 ⋅K) In the United States, U-value is expressed as British thermal units (Btu) per hour-square feet-degrees Fahrenheit: Btu/(h⋅ft 2 ⋅°F)
For example, consider a 5000 BTU/h (1465-watt cooling capacity) air-conditioning unit, with a SEER of 10 BTU/(W·h), operating for a total of 1000 hours during an annual cooling season (e.g., 8 hours per day for 125 days). The annual total cooling output would be: 5000 BTU/h × 8 h/day × 125 days/year = 5,000,000 BTU/year
It quantifies how effectively a material can resist the transfer of heat through conduction, convection, and radiation. It has the units square metre kelvins per watt (m 2 ⋅K/W) in SI units or square foot degree Fahrenheit–hours per British thermal unit (ft 2 ⋅°F⋅h/Btu) in imperial units. The higher the thermal insulance, the better a ...
The SI unit is watt (W). Another unit common in non-metric regions or sectors is the ton of refrigeration, which describes the amount of water at freezing temperature that can be frozen in 24 hours, equivalent to 3.5 kW or 12,000 BTU/h. [1] [2] [3]
The British imperial units and U.S. customary units for both energy and work include the foot-pound force (1.3558 J), the British thermal unit (BTU) which has various values in the region of 1055 J, the horsepower-hour (2.6845 MJ), and the gasoline gallon equivalent (about 120 MJ). Log-base-10 of the ratios between various measures of energy
HSPF is defined as the ratio of heat output (measured in BTUs) over the heating season to electricity used (measured in watt-hours). [1] [2] It therefore has units of BTU/watt-hr. The higher the HSPF rating of a unit, the more energy efficient it is. An electrical resistance heater, which is not considered efficient, has an HSPF of 3.41. [3]
The ratings are based on EPA's formula, in which 33.7 kilowatt hours of electricity is equivalent to one gallon of gasoline (giving a heating value of 115,010 BTU/US gal), and the energy consumption of each vehicle during EPA's five standard drive cycle tests simulating varying driving conditions.