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Community and Q&A

Turning off/setting back ductless minisplits, kwh, efficiency, and more

WildBunchFarm | Posted in Energy Efficiency and Durability on

So I talked to an LG engineer today (hint: if you have questions about minisplit performance, don’t call tech support, find the number to a local manufacturer and ask to talk to their engineer).

My 4 ton LG LMU48HV condenser can cool down to 14,400 btus. At that minimum, the system will use around 900 watts. This was actually verified by my Efergy Elite monitor, which showed that during 82 degree outside temperature, 3 of my indoor units were on, and it showed a pretty constant energy use of 900 watts for the 8 hours that it was on (2 pm – 10 pm).

I am hoping this means that my system isn’t short cycling. If my math is correct, it would mean a COP of 4.69. I am assuming this is pretty good. Of course, it’s not much of a temperature difference between indoor and outdoor temperature.

My problem is that sometimes the indoor units keep the condenser on even after the set temperature is reached. In my experience, minisplits are notorious for overshooting by as much as 5 degrees. For LG models, you can reset the unit to overshoot by just 2 degrees, but sometimes that doesn’t work and you have to physically relocate the thermostat.

So sometimes my indoor units continue to run even after my set temperature is reached and after the outdoor temperature has dropped lower than my set point. I have always read that you should set minisplits and forget it. But in my case, I find that actually setting back or turning off the indoor unit can save me some money. This usually happens at around 7-9 pm when the temperature drops off, but for some reason my indoor units keep running. I just turn it off, open up my windows, and I see my energy monitor drop down to a few watts.

I figure I can do this in the morning too if I am at home. Turn on the system when it is needed at around 10 am. This could potentially shave off at least 2 or 3 kwh every day.

After much headache getting the system to operate correctly (the system was overcharged by 3 pounds), I think I’m happy with the LG ductless multisplit system. My base load for anything non-HVAC is 900 kwh/month. With that number, I estimate that our annual heating/cooling load will be around 6600 kwh/year. Not bad for a 2800 square foot living area + 1600 square foot conditioned basement in Zone 4.

With all this being said, would people still recommend to set it and forget it in my circumstance? Secondly, I need some confirmation – are these good efficiency numbers in my case or could I do better?


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  1. GBA Editor
    Martin Holladay | | #1

    Depending on where you live, and depending on the outdoor humidity levels -- in many parts of North America, hot temperatures are accompanied by high outdoor humidity -- opening the windows in the evening may be false economy. The next morning, when you close your windows and turn your air conditioner back on, the air conditioner has to struggle to remove all the humidity that you invited into the house by opening your windows.

  2. WildBunchFarm | | #2

    Good point. I think maybe my system would only work during the "shoulder" months that don't usually come with high humidity. It appears right now in September, the humidity levels are not so high.

  3. Jon_R | | #3

    I ran some perhaps representative numbers and agree - the savings look minimal. Dryer/cooler nights help (less moisture uptake and more thermal storage).

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