Reversals
Cases where the advice everyone repeats does not survive contact with people who own the thing.
Reversals
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Every 1500-watt space heater produces exactly the same heat
VerdictNo. A 1500-watt electric heater converts essentially all of that electricity into heat, so every one of them puts out about 5,100 BTU per hour regardless of brand, price, or the word on the front.
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The dehumidifier didn't get weaker in 2019. The test did.
VerdictBecause the government changed the test, not the machines. From June 2019 portable dehumidifiers are tested at 65°F instead of 80°F, to reflect the cool basements they actually get used in.
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Air purifier room-size claims quietly assume you'll accept dirtier air
VerdictWork from CADR, not from the square footage printed on the box. AHAM's certified room size assumes 4.8 air changes per hour and works out to smoke CADR × 1.55 square feet — which is the same thing as the rule of thumb that CADR should be at least two-thirds of your floor area.