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Zero Energy Buildings - "Zero" of What? - Energy:Minute

"Zero energy" is a term we'll see applied to more and more buildings. It means the building produces as much energy on site as it uses. But that's not the whole story. There are many variations. Learn what they mean, in a minute.

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To be purely zero energy means not purchasing electricity or fuel, because all necessary power is generated on site all the time.

The term "net zero energy" means the building achieves that balance for the year, even though it buys grid power on some days, and on other days it sells excess energy back.

Then there's the question of where the purchases energy is measured. For a "net zero site energy" building, the purchased energy is measured at the meter. For a "net zero source energy" building it's measured at the generating station, so it accounts for the inefficiencies of transmission and distribution.

In a "net zero energy cost building," the purchases and credits from imported and exported energy are a wash. It's a purely financial metric, driven largely by local utility rates.

A "net zero energy emissions building" uses only emissions-free power sources, like wind or hydroelectric, or it buys offsets or credits to compensate for any carbon-emitting power it does buy.

That doesn't make the building carbon neutral, which is a whole other story. For more on that, listen to the Energy:Minute titled "The Meaning of Zero."