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The therm (symbol, thm) is a non-SI unit of heat energy equal to 100,000 British thermal units (BTU), [1] and approximately 105 megajoules, 29.3 kilowatt-hours, 25,200 kilocalories and 25.2 thermies. One therm is the energy content of approximately 100 cubic feet (2.83 cubic metres) of natural gas at standard temperature and pressure .
The Btu should not be confused with the Board of Trade Unit (BTU), an obsolete UK synonym for kilowatt hour (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.
North American domestic analog (Ferraris disk) electricity meter. Electricity meter with transparent plastic case (Israel) An electricity meter, electric meter, electrical meter, energy meter, or kilowatt-hour meter is a device that measures the amount of electric energy consumed by a residence, a business, or an electrically powered device over a time interval.
Although convective heat transfer can be derived analytically through dimensional analysis, exact analysis of the boundary layer, approximate integral analysis of the boundary layer and analogies between energy and momentum transfer, these analytic approaches may not offer practical solutions to all problems when there are no mathematical models applicable.
So, for a boiler that produces 210 kW (or 700,000 BTU/h) output for each 300 kW (or 1,000,000 BTU/h) heat-equivalent input, its thermal efficiency is 210/300 = 0.70, or 70%. This means that 30% of the energy is lost to the environment. An electric resistance heater has a thermal efficiency close to 100%. [8]
The term smart meter often refers to an electricity meter, but it also may mean a device measuring natural gas, water or district heating consumption. [1] [2] More generally, a smart meter is an electronic device that records information such as consumption of electric energy, voltage levels, current, and power factor.
More recently, the cost of solar in Japan has decreased to between ¥13.1/kWh to ¥21.3/kWh (on average, ¥15.3/kWh, or $0.142/kWh). [133] The cost of a solar PV module make up the largest part of the total investment costs. As per the recent analysis of Solar Power Generation Costs in Japan 2021, module unit prices fell sharply.
A 46 kW (157,000 BTU/h) heater, as might exist in a tankless heater, would take about 15 minutes to do this. At $1 per therm, the cost of the gas would be about 40 cents. In comparison, a typical 230 L (60 US gal) tank electric water heater has a 4.5 kW (15,000 BTU/h) heating element, which at 100% efficient results in a heating time of about 2 ...