Common heat pump misconceptions

A disgruntled man stood up at an energy expo and demanded to know how heat pumps can work in 0 celsius. While someone eventually gave an answer it showed theres a lot of misconceptions out there!

This week is a quick debunking of common misconceptions around heat pumps, like how heat pumps don't work if its cold outside.

But first, one other quick word. An amazing book is launching on June 18th, called "My Efficient Electric Home Handbook", written by the energy efficiency guru himself Tim Forcey. Many know Tim as the creator of the Facebook group My Efficient Electric Home with its 120k+ active members and as an accredited home energy assessor who has visited thousands of homes to help homeowners become more energy efficient. Now we can add author to that list too.

I managed to buy an early copy this weekend and I can 100% recommend it is a great wealth of knowledge to have on hand to help guide anyone through the energy efficiency journey.

Funnily enough, Tim and I were at an energy expo here in Melbourne this past weekend. During one talk, a rather disgruntled man stood up during a Q&A session and demanded the panellists tell him how a heat pump could possibly create heat if it were -1 Celsius or colder outside. Things got a bit tense, and it wasn't until an ex-heatpump installer stood up to set the facts straight that everyone's blood pressure dropped.

So, realising that there is still some disinformation out there, I decided to touch on the heat pump facts and misconceptions this week.

Heat pumps are air conditioners that are the most efficient way to heat your air and water

If you're asking yourself what's a heat pump?

Then, you might know them from a few other names, like a reverse cycle air conditioner or as a HVAC. Regardless of naming it's the air conditioning unit we are all familiar with. One part sits outside with a big fan, and the other is on a wall inside blowing cold or hot air. They do also come in single unit if you're buying one to heat water.

Heat pumps are a modern marvel. They convert energy into hot or cold air at 300 to 600% efficiency when in their optimal set-up. That means for each unit of energy you buy from your energy provider you get three to six units of energy for heating or cooling your air.

This free energy comes from the engineering of the heat pump itself. Using an ingenuous design of compressing air and moving around chemical coolant, the heat pump can push hot or cool air into your home at an efficiency that gas appliances can't even dream of. If you want to know more, Tim has a great chapter on this in his book called "Heating and Cooling"!

And not only are heat pumps great at heating air inside the home but they can also heat water for the home as well. With the same huge efficiency gains heating water with a heat pump is by far the most efficient method you can pay for.

In my best David Attenborough accent, here we see a split system heat pump in the wild preparing to heat some water for the homeowners to enjoy. Marvellous.

Heat pumps will work down to -25C and more!

In Norway, 66% of homes currently have heat pumps. When I was a kid growing up in subzero temperatures in the northeast of the US, we had a heat pump unit blowing hot air into our home as the outside portion sat covered in snow.

Heat pumps do indeed lose efficiency when they get into subzero temperatures, but that's only because they have to work harder to pull in more hot air. Hot air still exists on the coldest of days. -1 Celsius seems cold for a person, but for a machine, it's just another lovely day.

If the heat pump can operate at 400% efficiency in optimal temperatures, then the efficiency has a long way to drop in colder temperatures. In a worse-case scenario for Australian alpine regions, it might operate at 100% efficiency. Out of the eleven million homes in Australia, there are probably only a few hundred homes on top of ski mountains that would have to consider the efficiency drops of heat pumps. Even then, they would only need to look into heat pumps that are more purpose-built for freezing temperatures.

And on the other hand, heat pumps can work in conditions up to 50 degrees Celsius and more, depending on the unit. And on the chance you're way out in the bush then you can definitely find heat pumps with higher maximums.

Balancing the upfront cost of purchasing and installing a heat pump

I did an analysis of heat pump purchasing costs and cost to run a few months back. If there is interest, I can do a new one.

Heat pumps might cost more to purchase and install but the savings over the lifetime of the unit will more than make up for that cost. Between gas and heat pumps, in the long run, you save more with the heat pump.

Gas is cheaper per megaJoule, I currently pay 3.1¢/MJ here in Melbourne. And my electricity is more expensive, my rate current rate is 22.7¢ kWh. But one-kilowatt hour of electricity is equal to 3.6 megaJoules of gas energy, so our gas is equivalent to 11¢ per kilowatt in a like for like energy conversion.

Heat pumps are 300% to 600% efficient, whereas gas heaters are around 80% efficient at best.

You might see the issue in that fact alone. To produce the same amount of energy from the gas heater to equal the high efficiency of the heat pump, we need to use far more gas energy. If our gas costs us 11¢ per kilowatt hour, then we are looking at 33¢ to 66¢ in gas to equal the performance of one unit of energy from a heat pump, which originally only cost 22.7¢.

Even if electricity costs more than gas, it doesn't matter. The efficiency of a heat pump makes up for it and more. You would really need to skew the numbers quite significantly for gas to come out on top, and in 2024, it's not possible. Electricity is becoming more abundant with the uptake of solar and gas is on its way out, if anything these numbers will continue to move in the favour of heat pumps over the coming years.