BTU/hr to Watts Conversion. It is a conversion calculator that is used to convert the power in BTU per hour (BTU/hr.) to power in Watts (W). The first step of using this converter is to enter the value of BTU per hour in the blank text field. ››Definition: Btu. The British thermal unit (BTU or Btu) is a non-metric unit of energy, used in the United States and, to a lesser extent, the UK (where it isgenerally only used for heating systems).

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The British thermal unit (Btu or BTU) is a traditional unit of heat; it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. It is also part of the United States customary units.^[1] Its counterpart in the metric system is the calorie, which is defined as the amount of heat required to raise the temperature of one gram of water by one degree Celsius.^[2] Heat is now known to be equivalent to energy, for which the SI unit is the joule; one BTU is about 1055 joules. While units of heat are often supplanted by energy units in scientific work, they are still used in many fields. As examples, in the United States the price of natural gas is quoted in dollars per million BTUs.^[3][4]

BTU Calculator The BTU Calculator estimates the number of BTUs required to heat or cool homes based on the dimensions, insulation conditions, and the desired temperature changes. The desired temperature change is the necessary increase/decrease from outdoor temperature to reach the desired indoor temperature.

• 1Definitions
• 2Conversions

Definitions[edit]

A BTU was originally defined as the amount of heat required to raise the temperature of 1 avoirdupois pound of liquid water by 1 degree Fahrenheit at a constant pressure of one atmosphere.^[5] There are several different definitions of the BTU that are now known to differ slightly. This reflects the fact that the temperature change of a mass of water due to the addition of a specific amount of heat (calculated in energy units, usually joules) depends slightly upon the water's initial temperature. As seen in the table below, definitions of the BTU based on different water temperatures vary by up to 0.5%.

Prefixes[edit]

Units kBtu are used in building energy use tracking and heating system sizing. Energy Use Index (EUI) represents kBtu per square foot of conditioned floor area. 'k' stands for 1,000.

The units MBtu and MMBtu are used in the natural gas and other industries to indicate 1,000 and 1,000,000 BTUs, respectively.^[11][12] There is an ambiguity in that the metric system uses the prefix 'M' to indicate one million (1,000,000), and 'MBtu' is also used to indicate one million BTUs.^[13] Because of this ambiguity, some authors have deprecated the use of MBtu.^[12]

Energy analysts accustomed to the metric 'k' for 1,000 are more likely to use MBtu to represent one million, especially in documents where M represents one million in other energy or cost units, such as MW, MWh and $.

The unit therm is used to represent 100,000 (or 10⁵) BTUs.^[11] A decatherm is 10 therms or one MBtu (million Btu). The unit quad is commonly used to represent one quadrillion (10¹⁵) BTUs.^[13]

Conversions[edit]

One Btu is approximately:

• 1.054 to 1.060 kJ (kilojoules)
• 0.2931 W⋅h (watt hours)
• 252 to 253 cal (calories)
• 0.25 kcal (kilocalories)
• 25,031 to 25,160 ft⋅pdl (foot-poundal)
• 778 to 782 ft⋅lbf (foot-pounds-force)
• 5.40395 (lbf/in²)⋅ft³
• 1.730735 W/(m⋅K)

A Btu can be approximated as the heat produced by burning a single wooden kitchen match or as the amount of energy it takes to lift a one-pound (0.45 kg) weight 778 feet (237 m).^[14]

For natural gas[edit]

• In natural gas pricing, the Canadian definition is that 1 MMBtu ≡ 1000000 Btu ≡ 1.054615 GJ.^[15]
• The energy content (high or low heating value) of a volume of natural gas varies with the composition of the natural gas, which means there is no universal conversion factor for the number of Btu to volume. 1 standard cubic foot of average natural gas yields ≈ 1030 Btu (between 1010 Btu and 1070 Btu, depending on quality, when burned)
• As a coarse approximation, 1000 ft³ of natural gas yields ≈ 1 MMBtu ≈ 1 GJ
• For natural gas price conversion 1000 m³ ≈ 36.906 MMBtu and 1 MMBtu ≈ 27.096 m³

As a unit of power[edit]

When used as a unit of power for heating and cooling systems, Btu per hour (Btu/h) is the correct unit, though this is often abbreviated to just 'Btu'.^[16]MBH—thousands of Btus per hour—is also common.^[17]

• 1 watt is approximately 3.41214 Btu/h^[18]
• 1000 Btu/h is approximately 293.1 W
• 1 horsepower is approximately 2544 Btu/h, or $\frac{{\displaystyle 1}}{\sqrt{2}}$ Btu/s

Associated units[edit]

• 1 ton of cooling, a common unit in North American refrigeration and air conditioning applications, is 12,000 Btu/h (3.52 kW). It is the rate of heat transfer needed to freeze 1 short ton (907 kg) of water into ice in 24 hours.
• In the US and Canada, the R-value that describes the performance of thermal insulation is typically quoted in ft²⋅°F⋅hr/Btu. For one square foot of the insulation, one BTU per hour of heat flows across the insulator for each degree of temperature difference across it.
• 1 therm is defined in the United States and European Union as 100,000 Btu—but the U.S. uses the Btu_{59 °F} while the EU uses the Btu_IT. The therm is used in natural gas pricing in the United Kingdom.^[19]
• 1 quad (short for quadrillion Btu) is 10¹⁵ Btu, which is about 1 exajoule (1.055×10¹⁸ J). Quads are used in the United States for representing the annual energy consumption of large economies: for example, the U.S. economy used 99.75 quads in 2005.^[20] One quad/year is about 33.43 gigawatts.

The Btu should not be confused with the Board of Trade Unit (B.O.T.U.), which is a much larger quantity of energy (1 kW⋅h or 3,412 Btu).

The Btu is often used to express the conversion-efficiency of heat into electrical energy in power plants. Figures are quoted in terms of the quantity of heat in Btu required to generate 1 kW⋅h of electrical energy. A typical coal-fired power plant works at 10500 Btu/kW⋅h, an efficiency of 32–33%.^[21]

The centigrade heat unit (CHU) is the amount of heat required to raise the temperature of one pound of water by one degree Celsius. It is equal to 1.8 BTU or 1899 joules.^[22] This unit was sometimes used in the United Kingdom as an alternative to BTU but is now obsolete.

See also[edit]

References[edit]

1. ^In a short note, Woledge notes that the actual technical term 'British thermal unit' apparently originated in the United States, and was subsequently adopted in Great Britain. See Woledge, G. (30 May 1942). 'History of the British Thermal Unit'. Nature. 149 (149): 613. Bibcode:1942Natur.149..613W. doi:10.1038/149613c0.
2. ^Hargrove, James L. (2007). 'Does the history of food energy units suggest a solution to 'Calorie confusion'?'. Nutrition Journal. 6: 44. doi:10.1186/1475-2891-6-44. PMC2238749. Archived from the original on 1 August 2017.
3. ^'Henry Hub Natural Gas Spot Price'. U.S. Energy Information Administration. Archived from the original on 1 August 2017.
4. ^ ^abThe Btu used in US natural gas pricing is 'the amount of heat required to raise the temperature of one (1) pound of avoirdupois pure water from fifty-eight and five tenths degrees (58.5) Fahrenheit to fifty-nine and five tenths degrees (59.5) Fahrenheit at a constant pressure of 14.73 pounds per square inch absolute.' See 'Chapter 220: Henry Hub Natural Gas Futures'(PDF). NYMex Rulebook. New York Mercantile Exchange (NYMex). Archived(PDF) from the original on 10 November 2016. Retrieved 6 January 2017.
5. ^ ^abcSmith, J. M.; Van Ness, H. C.; Abbott, M. M. (2003). Introduction to Chemical Engineering Thermodynamics. B. I. Bhatt (adaptation) (6 ed.). Tata McGraw-Hill Education. p. 15. ISBN0-07-049486-X.
6. ^ ^abThe pound is now defined as 453.59237 grams; see 'Appendix C of NIST Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices, General Tables of Units of Measurement'(PDF). United States National Bureau of Standards. p. C-12. Archived from the original(PDF) on 26 November 2006. One degree Fahrenheit is now defined as exactly 5/9 of a degree Celsius.
7. ^Thompson, Ambler; Taylor, Barry N. 'Guide for the Use of the International System of Units (SI) 2008 Edition'(PDF). National Institute of Standards and Technology (NIST). p. 58. Archived(PDF) from the original on 3 June 2016. NIST Special Publication 811.
8. ^ ^abSørensen, Bent (2008). Renewable Energy Focus e-Mega Handbook. Academic Press. p. 5. ISBN9780123747068.
9. ^Koch, Werner (2013). VDI Steam Tables (4 ed.). Springer. p. 8. Published under the auspices of the Verein Deutscher Ingenieure (VDI).
10. ^Cardarelli, Francois (2012). Scientific Unit Conversion: A Practical Guide to Metrication. M.J. Shields (translation) (2 ed.). Springer. p. 19.
11. ^ ^ab'What are Mcf, Btu, and therms? How do I convert prices in Mcf to Btus and therms?'. U.S. Energy Information Administration. 6 April 2016. Archived from the original on 25 December 2016. Retrieved 30 December 2016.
12. ^ ^abPrice, Gary D. (2014). Power Systems and Renewable Energy: Design, Operation, and Systems Analysis. Momentum Press. p. 98.
13. ^ ^ab'Energy Units'. American Physical Society. Archived from the original on 31 December 2016. Retrieved 26 December 2016.
14. ^Energy and the Environment. Ristinen, Robert A. c. 2006, pp 13–14
15. ^'Energy Measurements'. Government of Alberta Province. Archived from the original on 20 January 2017. Retrieved 7 January 2017.
16. ^Ken Matesz (2010). Masonry Heaters: Designing, Building, and Living with a Piece of the Sun. Chelsea Green Publishing. p. 148.
17. ^'What is difference between BTU and MBH for house furnaces?'. Home Improvement Stack Exchange. Retrieved 26 November 2018.
18. ^['2009 ASHRAE Handbook - Fundamentals (I-P Edition)'. Archived from the original on 17 October 2015. Retrieved 21 September 2015.? 2009 ASHRAE Handbook – Fundamentals (I-P Edition)]. (pp: 38.2). American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc
19. ^'The GB gas wholesale market'. Office of Gas and Electricity Markets. Archived from the original on 30 September 2013. Retrieved 13 January 2013. The wholesale gas market in Britain has one price for gas irrespective of where the gas comes from. This is called the National Balancing Point (NBP) price of gas and is usually quoted in price per therm of gas.
20. ^Husher, John Durbin (2009). Crises of the 21st Century: Start Drilling-The Year 2020 Is Coming Fast. iUniverse. p. 376. ISBN9781440140549. OCLC610004375..
21. ^Bellman, David K., ed. (18 July 2007). 'Electric Generation Efficiency'(PDF). National Petroleum Council (NPC). Archived from the original(PDF) on 20 November 2008. Retrieved 30 March 2012. Working Document of the NPC Global Oil & Gas Study.
22. ^http://www.diracdelta.co.uk/science/source/c/e/centigrade%20heat%20unit/source.html#.WJ0QuB1AqFoArchived 25 December 2016 at the Wayback Machine

External links[edit]

• 'The Units of Measurement Regulations 1995'. www.legislation.gov.uk. HMSO. 13 July 1995. Retrieved 23 February 2018.
• 'Natural Gas: A Primer'. www.nrcan.gc.ca. Natural Resources Canada. 27 November 2015. Retrieved 23 February 2018.

AC BTU Calculator

Use this calculator to estimate the cooling needs of a typical room or house, such as finding out the power of a window air conditioner needed for an apartment room or the central air conditioner for an entire house.

General Purpose AC or Heating BTU Calculator

This is a general purpose calculator that helps estimate the BTUs required to heat or cool an area. The desired temperature change is the necessary increase/decrease from outdoor temperature to reach the desired indoor temperature. As an example, an unheated Boston home during winter could reach temperatures as low as -5°F. To reach a temperature of 75°F requires a desired temperature increase of 80°F. This calculator can only gauge rough estimates.

What is a BTU?

The British Thermal Unit, or BTU, is an energy unit. It is approximately the energy needed to heat one pound of water by 1 degree Fahrenheit. 1 BTU = 1,055 joules, 252 calories, 0.293 watt-hour or the energy released by burning one match. 1 watt is approximately 3.412 BTU per hour.

BTU is often used as a point of reference for comparing different fuels. Even though they're physical commodities and quantified accordingly, such as by volume or barrels, they can be converted to BTUs depending on the energy or heat content inherent in each quantity. BTU as a unit of measurement is more useful than physical quantity because of fuel's intrinsic value as an energy source. This allows many different commodities with intrinsic energy properties to be compared and contrasted; for instance, one of the most popular is natural gas to oil.

BTU can also be used pragmatically as a point of reference for the amount of heat that an appliance generates; the higher the BTU rating of an appliance, the greater the heating capacity. As for air conditioning in homes, even though ACs are meant to cool homes, BTUs on the technical label refer to how much heat the air conditioner can remove from their respective surrounding air.

Size and Ceiling Height

Obviously, a smaller area room or house with shorter lengths and widths require fewer BTUs to cool/heat. However, volume is a more accurate measurement than area for determining BTU usage because ceiling height is factored into the equation; each three-dimensional cubic square foot of space will require a certain amount of BTU usage to cool/heat accordingly. The smaller the volume, the fewer BTUs are required to cool or heat.

The following is a rough estimation of the cooling capacity a cooling system would need to effectively cool a room/house based only on the square footage of the room/house provided by EnergyStar.gov.

Btu Hr To Watts Converter Chart

Insulation Condition

Thermal insulation is defined as the reduction of heat transfer between objects in thermal contact or in range of radiative influence. The importance of insulation lies in its ability to lower BTU usage by managing as much as possible the inefficient wasting of it due to the entropic nature of heat – it tends to flow from warmer to cooler until there are no longer temperature differences.

Btu Hr Conversion

Generally, newer homes have better insulating ability than older homes due to technological advances as well as more strict building code. Owners of older homes with dated insulation that decide to upgrade will not only improve on the ability for the home to insulate (resulting in friendlier utility bills and warmer winters), but also have the value appreciation of their homes.

Btu Hr To Watts Converter Chart Online

The R-value is the commonly used measure of thermal resistance, or ability of heat to transfer from hot to cold through materials and their assembly. The higher the R-value of a certain material, the more it is resistant to the heat transfer. In other words, when shopping for home insulation, higher R-value products are better at insulating, though they're usually more expensive.

When deciding on the proper input of insulation condition into the calculator, use generalized assumptions. A beach bungalow built in the 1800s with no renovations should probably be classified as poor. A 3-year-old home inside a newly developed community most likely deserves a good rating. Windows normally has poorer thermal resistance than walls. Therefore, a room with lots of windows normally means poor insulation. When possible try to install double glazed windows to improve insulation.

Desired Temperature Increase or Decrease

To find the desired change in temperature to input into the calculator, find the difference between the unaltered outdoor temperature and the desired temperature. As a general rule of thumb, a temperature between 70 and 80°F is a comfortable temperature for most people.

For example, a house in Atlanta might want to determine the BTU usage during winter. Atlanta winters tend to hover around 45°F with chances to reach 30°F occasionally. The desired temperature of the dwellers is 75°F. Therefore, the desired temperature increase would be 75°F - 30°F = 45°F.

Homes in more extreme climates will obviously require more radical changes in temperature, resulting in more BTU usage. For instance, heating a home in Alaskan winter or cooling a home during a Houston summer will require more BTUs than heating or cooling a home in Honolulu, where temperatures tend to stay around 80°F year-round.

Btu Conversion To Watts

Other Factors

Obviously, size and space of house or room, ceiling height, and insulation conditions are very important when determining the amount of BTUs required to heat or cool a house, but there are other factors to keep in mind:

Btu Hr To Watts Converter Chart Calculator

• The number of dwellers residing inside the living spaces. A person's body dissipates heat into the surrounding atmosphere, requiring more BTUs to cool and fewer BTUs to warm the room.
• Try to place the air conditioner condenser on the shadiest side of the house, which will usually be north or east of it. The more the condenser is exposed to direct sunlight, the harder it must work due to the higher surrounding air temperature, which consumes more BTUs. Not only will placing it in a shadier area result in greater efficiency, but it will extend the life of the equipment. It is possible to try and place shady trees around the condenser, but keep in mind that condensers also require good surrounding airflow for best efficiency. Make sure neighboring vegetation does not interfere with the condenser, blocking air flow into the unit and choking it.
• Size of air conditioning condenser. Units too big cool homes too rapidly. Therefore, they don't go through the intended cycles, which were intentionally designed for out of the factory. This may shorten the lifespan of the air conditioner. On the other hand, if the unit is too small, it will run too often throughout the day, also overworking itself to exhaustion because it isn't being used efficiently as intended.
• Ceiling fans can assist in lowering BTU usage by improving air circulation. Any home or room can be a victim of dead spots, or specific areas of improper airflow. This can be the back corner of the living room behind a couch, the bathroom with no vent and a big window, or the laundry room. Thermostats placed in dead spots can inaccurately manage the temperatures of homes. Running fans can help to distribute temperatures evenly across the whole room or house.
• The color of roofs can affect BTU usage. Darker surface absorbs more radiant energy than a lighter one. Even dirty white roofs (with noticeably darker shades) compared to newer, cleaner surfaces resulted in noticeable differences.
• Efficiency decrease of the heater or air conditioner with time. Like most appliance, the efficiency of the heater or air conditioner decrease with usage. It is not uncommon for an air conditioner to loss 50% or more of its efficiency when running with insufficient liquid refrigerant.
• Shape of the home. A long narrow house has more wall than a square house with the same square footage, which means heat loss.