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The most expensive thing people do with a heat pump in winter is not leaving it on. It is cranking it to 28 degrees the moment they walk in cold, in the belief that a higher number heats the room faster. It does not, and that single habit is behind a lot of the scary power bills people blame on the heat pump itself. Set it right and you get a warm, healthy home and a running cost that barely moves. Here is the number to actually use, and why.
For living areas through an Auckland winter, set your heat pump to somewhere around 18 to 21 degrees. Eighteen is the minimum the World Health Organisation considers healthy for a home, and 20 to 21 is comfortable for most people. Bedrooms can sit lower, around 16 to 18 overnight.
That is genuinely it. Anything much above 21 in a living room is mostly burning power for very little extra comfort, and it is where bills start to climb without you feeling much warmer. If you take one thing from this article, it is that the low twenties, not the high twenties, is the sweet spot.
This is the myth worth killing. A heat pump runs at full output to reach whatever temperature you set, and it does not run any harder at 28 than it does at 20. Setting it to 28 does not make warm air arrive faster. All it does is tell the unit not to stop at 20, so it keeps pumping out heat, overshoots the temperature you actually wanted, runs far longer, and costs you more, often while you open a window because the room got too hot.
Set the temperature you actually want to feel, and the heat pump gets there just as quickly as if you had set it to 28. The number is a destination, not an accelerator.
A heat pump is at its most efficient holding a steady temperature, not being blasted on and off. Modern inverter units work by ramping up to reach your setpoint and then quietly modulating to hold it, sipping power rather than gulping it. Every time you switch it off and on again to a cold room, you force another full-power burst to climb back up.
So pick your temperature, put the unit on auto mode, and let it do its job. Auto mode manages the fan and output for you to keep the room at the setpoint efficiently. Steady and sensible beats hot-then-off every time, and it is easier on the unit too. All of this feeds straight into what your heat pump costs to run over the season.
Here is the rule of thumb that makes the setpoint matter. As a rough guide, every extra degree you ask for adds around ten percent to your heating energy. That means the difference between running at 20 and running at 24 is not small, it is a meaningfully bigger bill for warmth you probably do not need.
Turned around, it is the easiest saving in the house. Dropping your setpoint by a degree or two, and popping on a jumper, quietly trims the bill with no loss of real comfort. It is the closest thing to free money in home heating.
You do not need to hold a living-room temperature everywhere, all night. Bedrooms are comfortable cooler, so setting them around 16 to 18 overnight is plenty for good sleep and kinder to the bill. Rather than running a bedroom unit on high all night, use the timer to warm the room before you wake, or before you head to bed, so you are only paying for heat when you are actually there to feel it. The timer is one of the most underused money-savers on the remote.
One thing that alarms people in winter and makes them crank the temperature is the unit blowing cooler air, or pausing, on a cold damp morning. That is almost always a defrost cycle, and it is completely normal. When frost builds on the outdoor unit, the heat pump briefly reverses to melt it before carrying on heating. It is the unit looking after itself, not a fault, and it passes in a few minutes. If the air stays cold well beyond that, that is a different issue worth reading up on in our guide to a heat pump that is not heating.
Two quick tweaks make the setpoint work harder for you. Aim the louvres downward, because warm air rises, and pointing the flow down pushes heat into the living space rather than letting it collect at the ceiling. And leave the fan on auto rather than its lowest setting, so the unit can move enough warm air to actually reach you. Small things, but they help the room feel warmer at the same setpoint.
If you have the setpoint sensible and the unit is still fighting to warm the room, the culprit is usually size, not the thermostat. An undersized heat pump runs flat out and never quite holds temperature on the coldest nights, which sends people reaching for a higher number that only costs more. It is worth checking that the unit is right for the room using our heat pump size calculator. And if you are comparing the cost of heating this way against the plug-in heater you used to use, our look at portable heaters versus a heat pump shows just how much cheaper a heat pump is to run at a sensible setpoint.
Getting the most from a heat pump in winter is less about the machine and more about the number on the remote. Set it in the low twenties, run it steady on auto, use the timer, and let it do what it is brilliant at, which is heating your home cheaply.
Varcoe has kept Auckland homes warm since 1975, and if your heat pump is set sensibly but still not keeping up, we can check whether it is the right size and running as it should. Get in touch for a free assessment, call us on 0800 088 888, or email info@varcoe.co.nz, and we will make sure your heat pump is warming your home without warming your bill.
Around 18 to 21 degrees for living areas, and about 16 to 18 for bedrooms overnight. Eighteen is the minimum considered healthy for a home, and the low twenties is comfortable without pushing your bill up.
No. A heat pump runs at full output to reach whatever you set, so 28 does not heat faster than 20. It just overshoots, runs longer and costs more. Set the temperature you actually want to feel.
Holding a steady, sensible temperature on auto mode is usually more efficient than switching it off and on, because each restart forces a full-power burst to reheat a cold room. Use the timer so it only runs when you are there.
Around 16 to 18 degrees is comfortable for sleep and easier on the bill. Use the timer to warm the room before bed or before you wake rather than running it high all night.
Almost always a defrost cycle, which is normal. The unit briefly reverses to melt frost off the outdoor coil, then carries on heating within a few minutes. If it stays cold much longer, that points to a heating fault worth investigating.
As a rough guide, each extra degree adds around ten percent to your heating energy, so running at 24 instead of 20 costs noticeably more. Dropping a degree or two is the easiest saving there is.
We can check your heat pump is the right size for the room and running as it should.
