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Community and Q&A

Does the EER matter on a ductless mini-split?

wlarsen | Posted in Energy Efficiency and Durability on

The Energy Star requirements for ductless mini-splits are identical to split air-source heat pumps, with SEER, EER, and HSPF efficiency standards. However, several utility programs have chosen to drop the EER requirement (e.g. Energize Connecticut).

Does the EER matter on a ductless mini-split? Why or why not?


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  1. wlarsen | | #1

    Follow-up Question: Does climate zone make a difference in the relevance of the EER?

  2. GBA Editor
    Martin Holladay | | #2

    EER is the cooling capacity of the appliance (in Btu/h) at an outdoor temperature of 95°F divided by the current draw of the appliance in watts.

    SEER is the total cooling output (in Btu/h) over the cooling season divided by the total electrical energy input (in watt-hours) over the cooling season.

    The relationship between SEER and EER depends on location, because equipment performance varies with climate factors like air temperature and humidity.

    Neither metric tells the whole story, and it's possible to game any rating system by designing equipment with the aim of maximizing either the EER or SEER (rather than maximizing a more useful performance goal).

    In most cases, high-EER equipment tends to have a high SEER, so it's perfectly reasonable for a utility program to simplify their program requirements by using a single metric.

  3. wlarsen | | #3

    Thanks Martin! Out of curiosity, is there also a standard humidity or climate zone at which the EER is tested? Or are there climate-zone specific ratings?

  4. GBA Editor
    Martin Holladay | | #4

    I'm not sure. I know that the EER test is usually conducted with indoor conditions at 80°F and 50% RH, and with outdoor conditions at 95°F.

    I'm not sure about the outdoor RH requirements for the test procedure.

  5. user-626934 | | #5

    Outdoor RH doesn't effect cooling performance for air source heat pumps / AC units. In summer/cooling mode, the outdoor coil temperature is warmer than the outdoor air, so there's no condensation / phase change / moisture removed from the outdoor air.

  6. GBA Editor
    Martin Holladay | | #6

    Thanks. Makes sense.

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