I (with the help of an HVAC professional) installed a ductless, split system. It's a 24,000 BTU, single head system. What surprised me is how much energy (relative to everything else in the house) it uses while in the off/stand-by mode.

It's on a dedicated circuit, and I calculated using my Aeotec Home Energy Monitor that it's continuously using about 130 W with no visible operation. The head/air handler is "off", no noise from the compressor, compressor fan is not moving, etc.

Is this common for systems to use this much energy in stand-by or does it indicate something may be wrong with the wiring or connections?

Additional notes:

  1. My system doesn't make an off/standby distinction. There is just an off button on the remote. I use the terms interchangeably b/c while it is "off" it is still drawing 130 W of power.
  2. The home energy monitor uses clamps (one on each incoming 120V main line). I know it's ~ 130 W by monitoring the usage for 5 min, throwing the 2 pole breaker for the A/C, calculating the diff, and then turning it back on to verify. It appears to be fairly accurate for other circuits that I've tested (e.g. ~15 W for an LED lamp, < 1 W for an in-panel surge protector, ~60-70 W for the fridge, spikes +1000 W for the microwave, etc.)

Home Energy Monitor Report

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    Off and Standby aren't the same thing. Standby mode means the unit is staying ready to kick in instantly. – The Evil Greebo Jun 30 '17 at 16:15
  • To clarify, my system doesn't make an off/standby distinction. There is just a single off button on the remote. I use the terms interchangeably b/c while it is "off" it is still drawing 130 W of power. – Keith Bentrup Jun 30 '17 at 16:39
  • Does it determine when to turn on, or is there an external thermostat which does? If no thermostat, that's what that power is for – mmathis Jun 30 '17 at 16:40
  • How does the "Aeotec Home Energy Monitor" determine energy usage by the system? E.g., does the monitor have an inline sensor through which the units is plugged in? Does it monitor load through a breaker or wire at the subpanel? – feetwet Jun 30 '17 at 16:56
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    The Aeotec uses clamps on the main breakers. That tells it nothing about the load on a particular circuit. It is guessing, and it could be fooled by other effects. As such it is not conclusive. I'd want a clamp meter on one of the hots going to the unit. – Harper - Reinstate Monica Jun 30 '17 at 17:32

Your unit is probably a Heat Pump. I sell these and I'm not aware of any companies that still sell a/c only units since the cost difference was minimal they have been phased out. So being a heat pump it would have a crankcase heater either under or wrapped around the compressor. As long as the main power switch is on the heater will be energized whenever the compressor is off. That is to keep the oil in the system liquid so it can mix with the refrigerant gas when in operation. It is a resistance type heater so the wattage seems reasonable.

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I have a building with a Fujitsu heat pump that is not used in the summer so I turned off the breaker for the unit and everything else in the building was off. I monitored usage on the supplier web site and had "0" usage for 2 months. A week ago I noticed that the site was showing between 4kw and 6kw usage each day. When I checked, someone had turned on the heat pump breaker by mistake. So, the heat pump was consuming $18 to $28 in electricity per month when turned off at the remote!

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In general most equipment or appliances that have electronic controls will use some AC while the equipment is in the off position. You just mentioned you turn your unit on and off with a remote. So there must be power to sense the remote and its calls to start etc. Also the need for the consumer to want instant start for their equipment, manufacturer's design power circuits that remain continually warm so they get that response.

All that being said. We would really not know if the amount you measured is accurate, or is high or low by industry standards unless we had some sort of engineering data base that would give us that information. To get that you would probably have to be part of that type of manufacturer.

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    This is about 200x as high as what it should be for a standby appliance. I'm not sure about the US, but I think Euro standards require <0.5W. – SomeoneSomewhereSupportsMonica Jul 1 '17 at 2:47
  • A standby air conditioner will often keep it's compressor pump active to keep the coils ready to cool effectively as soon as the demand is there. – The Evil Greebo Jul 1 '17 at 11:42

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