Aircon Standby Power: What Stays on When You Switch Off

The remote never reaches the supply. It sends a signal to a controller, and that controller has to be listening when the next signal arrives. Staying ready to hear the next one costs power, so a machine parked by the remote holds a state rather than sitting dead like a switched-off kettle.

What holds that state is short and specific: the receiver, the board reading it, the panel light or display, and the clock behind any timer setting. A network module counts too, because a module that has dropped off the home network cannot be reached by an app. None of this moves air or refrigerant; all of it waits.

The draw is buying something, which a warning about phantom load usually leaves out. A system without supply cannot be reached at all: a timer does not count down, and an app cannot wake the machine before anybody gets home. The indoor side of the fixed draw pays for those conveniences.

Standby and off are separate conditions in the measurement world, not two words for one thing. IEC 62301, the standard NEA names for standby power testing on regulated aircon, treats standby mode and off mode as distinct states with distinct readings. A split system parked by its remote sits in the first; reaching the second means the supply itself has gone.

Two neighbouring questions get settled elsewhere. Whether a timer or a hand on the remote is the better way to end a cooling session is a runtime question, answered by the timer versus manual off guide. What the isolator is, and why its supply is kept clear of other loads, belongs with the dedicated power point. Standby is what is left after both are decided.

The outdoor unit runs a board of its own and has its own reason to keep it alive. It has to hear the indoor side and be ready to act. Proximity to the remote is not what makes a system responsive; being powered is, and the machine on the ledge is powered whether or not anybody indoors is thinking about it.

Some designs go further and keep the compressor conditioned while the machine sits idle. Refrigerant in a stopped system migrates towards the coldest point and can settle into the compressor oil, and oil carrying dissolved refrigerant does not lubricate properly at the next start. A small warming load holds the oil above the point where that settling happens.

That load is why an outdoor figure can be larger than anything the indoor unit accounts for, and why one number describes it badly. A warming load is usually governed by temperature rather than left permanently energised, so what a machine holds while idle shifts with the weather. The crankcase heater is its own subject.

Manufacturer literature shows the load is doing real work. Installation instructions commonly direct that the outdoor unit be left energised ahead of the first compressor start, so the warming load has finished before anything turns. Guidance of that kind exists because starting a compressor on refrigerant-loaded oil damages it.

The standby figure attached to a registered model is measured, not estimated. NEA names IEC 62301 as the standby power test standard for regulated aircon, in both its 2005 and 2011 editions. A supplier's test report has to be produced against it before the model can be registered for sale here. The figure is the outcome of a defined procedure.

The standard defines how to measure and nothing beyond that. IEC states plainly that it specifies no maximum on power or energy consumption. Any ceiling is a separate instrument, belonging to the supply standard rather than the test method. Where that ceiling sits today, and how it scales across several indoor units, is set out in the MEPS guide.

Measurement happens with the machine parked in a controlled room, doing nothing, under conditions written to be repeatable across laboratories. Repeatability is what makes the figure useful for setting two models side by side, and it is also what prevents it describing a real ledge on a real night. Out there, a temperature-governed load may or may not be drawing.

Read the number as a comparison and then stop. It answers which of two models holds less while idle, tested on a single basis. What the machine outside your window holds tonight is a separate question, and no arithmetic on a declared figure converts one into the other.

Finding the figure for a specific model is a documentation question rather than a shop-floor one. It sits behind the registration as part of the test report. A printed specification sheet may or may not carry it forward. Ask for the model's own paperwork: a standby figure nobody can trace to a test report is an assertion.

Standby is a floor under the bill rather than a movement in it. It reads the same in a month of heavy cooling as in a month with none, because nothing about it responds to use. That single property explains both why households miss it and why it makes a poor suspect when a statement looks wrong.

Small and continuous is the shape people estimate worst. Any one hour of it is beneath noticing, so the draw gets discounted to zero; the hours themselves never stop, which makes zero the wrong figure. Running consumption has the opposite shape, and it collects all the attention.

The practical consequence is diagnostic. A bill that moved was not moved by standby, because standby did not move. Anything identical in every hour cannot account for a difference between two statements. Bill spikes have a page that works through the causes that do move.

Where standby matters most proportionally is where the aircon runs least. A household cooling one bedroom at night spreads that fixed draw across few running hours, so it forms a larger share of what the system costs. The share is largest precisely where the total is smallest, which is why chasing it rarely repays the attention.

The case for removing supply is real and narrow. It applies where a system will not be run for a long stretch, and it thins to nothing where the machine will be used again before the day is out. Length of disuse is the only variable that genuinely moves the answer.

Set against nightly use, the trade is poor on both sides at once. The saving is a fixed draw across hours the machine would have spent idle regardless. The cost is whatever protection that idle load provides, repeated every night, plus the need to remember to restore supply before the next start. A protective margin converted into a nightly chore is a margin somebody will eventually skip.

The isolator belongs in the arithmetic and usually gets left out. It sits outdoors, takes weather, and corrosion goes to work on its contacts. A switch worked rarely and one worked every night do not age alike, and a failing one produces symptoms that read like a fault in the machine behind it. The system stays silent when cooling is called for, or wakes on one attempt and ignores the next.

None of this is an instruction to go and operate anything. Whether a specific system should sit without supply is a judgement about that machine, and it needs somebody who knows what is inside it. The manual, the installer, or the technician who services it can answer it in one exchange. Deciding is the homeowner's part.

The honest summary is that standby is real, small, and mostly not where the money is. It earns understanding because the machine does not behave the way the remote implies, and because the supply decision gets made on poor reasoning in both directions. Cutting power to a flat standing empty is sensible; cutting it nightly buys a small saving with the protection that draw provided.

• •Does this system hold a load that conditions the compressor while idle? The manual answers it, and so does the installer.
• •How long is the machine genuinely going to sit? Anything counted in nights is not this situation.
• •Who restores supply before the system is next asked to run, and will they remember?
• •Is the isolator fit to be worked often, or has the ledge already had its way with the contacts?
• •Has anything larger been ruled out first? A fixed idle draw is the smallest lever on an aircon bill.