It emits more CO 2 per unit of heat than natural gas.

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He said well-designed systems can operate effectively in the UK, delivering in excess of three units of heat for every unit of electricity used to pump the heat in and around the property.

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They can carry five to 20 times more current in the same unit area while reducing the amount of energy lost as heat by 75-97% (depending on whether the current is alternating or direct), even after accounting for all the nitrogen-cooling paraphernalia.

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For every unit of energy to drive the compressor, the pump yields four units of heat.

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"An air-conditioning unit is just the physical manifestation of the Carnot Cycle - which is talking about heat exchange between two closed systems, " he droned.

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The standard measure for such things is the Scoville Heat Unit, or SHU, named after Wilbur Lincoln Scoville, a chemist who in 1912 developed a method of assessing the heat given off by capsaicin, the active ingredient in chili peppers.

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