Does a heater use more power if you turn it on and off throughout the day?

There's nothing like flicking on the heater to help you get out of bed in the morning.

But should you then turn it off once you're warmed up… only to turn it on again half an hour later, when you're back to feeling the chill?

It's going to depend on a ton of factors — like your home's insulation, what room you're trying to warm up, the type of heater you use, and even the time of day.

To find out more, I chatted with Peta Ashworth OAM, the director of the Curtin Institute for Energy Transition, and Xiaolin Wang, a senior lecturer in engineering who specialises in heating systems at the Australian National University.

Reverse cycle air conditioning

Whether you have a wall unit or a ducted set-up, your reverse cycle air conditioner's efficiency will vary throughout the day.

Dr Wang explains that aircon works by sucking heat from the air outside your home.

Theoretically, if you ran your aircon at 25 degrees when it was 25 degrees outside, it wouldn't cost you anything.

"[Whereas] if you want 25 degrees [inside] but outside it's -2, it's running very hard, at a low efficiency."

For this reason, Dr Wang recommends leaving your aircon between 18 and 22 degrees in winter, while consumer advocacy group CHOICE suggests setting it to 8 degrees warmer than the outside temperature.

Air conditioners have a sensor inside your home to monitor its temperature, and will work to get your home's climate to whatever number you've set.

Because of this, Dr Wang says it's best not to turn your aircon on and off.

She says if you heat your house for a while, then turn your heater off — only to switch it back on when it gets cold again — your aircon is going to have to work hard to get back to that desired temperature. She compares this surge to revving your car to get up a hill.

Whereas if it's on the same low temperature for one or two hours (that isn't too different from the outside temperature), it's going to run much more effectively and is unlikely to change your power bill, as you prevent the start-up energy cost that comes with frequently turning it on and off.

Because, staying with the car analogy, Dr Wang adds that powering your aircon on and off uses energy too, likening it to the burst of energy it takes to ignite your car.

She also suggests avoiding your aircons 'auto' function, as while it's "a smart function, it's not always smart".

"When it reaches 20 degrees [if that's your set temperature], the air conditioner thinks: Maybe I should stop.

"But then suddenly [the ambient room temperature has] dropped to 18, so it just starts again, with this on and off and on and off, which is using a lot of electricity."

And if you're leaving the house for less than two hours — to grab a coffee, or pick up kids from school — Dr Wang recommends leaving your aircon on.

Portable fan heaters and gas heaters

Dr Wang says when it comes to portable electric heaters, or gas systems, turning your device on and off isn't going to make much of a difference, as these heaters don't have the complex functions of an air conditioner.

If you're using a portable fan heater, Professor Ashworth says to remember that they tend to be less efficient.

"If it's just to warm you up in the mornings and off you go, [they're great].

"But you definitely wouldn't leave that on all day, because it would cost you a fortune."

She recommends checking the energy rating before buying one, as there's no point going for a cheap, inefficient model if you're never going to use it because it makes your power bill skyrocket.

If you've had the same heater for ages, it could be worth upgrading to a newer, more efficient model if it's in budget.

Professor Ashworth says portable slat or blade oil heaters tend to be more efficient to run.

While they take a little longer to heat up, they could be a better option if you're looking to have it on for most of the day.

Whatever type of heater you use, Dr Wang says leaving them on the 'low' setting should save you power if your room is not too big and the insulation is OK.

She adds that warm air rises, so if you have a small fan heater, leave it by your feet rather than up at your desk.

Keep the heat in, whatever system you're using

Then there are simple things you can do to keep the heat in your room or home.

"Put down the blinds, or you could get one of those old snakes to put at the bottom of the door," Professor Ashworth says.

"When I lived in an old Queenslander with a long corridor, I'd put a sheet up during the winter [to block the hallway].

Ultimately, what heating you use will depend on your specific needs and home.

Professor Ashworth says staff at your local appliance shop will likely be very knowledgeable, and able to help you find a heater that suits your needs.

"And if you just need to keep warm in bed, electric blankets are much cheaper than trying to heat a room.

"You've got to really personalise it."

This article contains general information only. You should consider obtaining independent professional advice in relation to your particular circumstances.