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It's an example of a good old scientifically flavored clickbait.

The energy efficiency of anything cannot exceed 100% (until I missed something groundbreaking in physics).

How can it be "click bait" if neither the title nor the headline contains that number? You have to read at least the first three paragraphs of the article to stumble about that number. The focus of the article is on the inexpensive design, not on its efficiency

The HN title has been changed. It used to refer to the 385 percent claim. Probably GP thought this was from the title.

It very much can exceed 100% and it’s not a measure invented for click bait purposes.

Look up heat pumps. You can make things hotter by moving heat than you could by directly heating it by burning fuel.

As another comment pointed out, it’s usually called the Coefficient of Performance in this case.

Which is to say this is click bait, because saying it has a COP of 3.85 isn’t anywhere near as sexy, whilst being technically more accurate.

The ‘more than 100%’ is only in comparison to a less efficient process. A heat pump itself is operating below 100% efficiency - it’s just kind of “cheating” by using an external source of external energy as one of its inputs in addition to the electricity running it.

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