Sure, the electricity that makes it to the heater gets turned into heat, but you have the losses in making and transmitting the power. Power plants have been known to get everything from 15 to a bit over 30 percent efficiency, then you lose a percent or three in your step up transformers, some more in long-distance transmission, and another little bit in the step down transformers.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.