These days, more and more people are becoming aware of heat pumps and their amazing efficiency. They’re so efficient that their performance often sounds unbelievable to people used to conventional heating systems. For example, it’s common to hear about heat pumps that deliver up to 400% energy efficiency when running in heating mode. It’s natural for numbers like that to prompt confusion. After all, how can a heating system be more than 100% efficient, anyway? Well, wonder no more! Here’s everything you need to know about heat pump efficiency and how they achieve such high numbers.
What’s Heating Efficiency?
When you hear people discuss the concept of heating efficiency, what they’re talking about is what percentage of the fuel you put into a heating system turns into usable heat. In an oil-burning system, you’d be talking about how many units of heat that burning one unit of oil yields. The same thing goes for natural gas burners.
The Efficiency of Conventional Heating Systems
Today, the most efficient oil and natural gas systems operate at an efficiency of around 98%. That means you only waste about 2% of the fuel you burn in such units. The rest escapes in the form of exhaust or gets lost due to incomplete combustion. Conventional heating systems do everything possible to capture as much of the heat the combustion process produces and turn it into usable heat for a building.
What Makes Heat Pumps So Different?
As their name suggests, heat pumps don’t create heat at all. Instead, they move it from one place to another, like a pump moves water. There’s no fuel source getting turned into heat. Instead, it captures heat energy from the outside air, pumps it indoors, and distributes it where you need it. The only electricity it uses goes toward operating the compressors and other components that make the system work.
That’s the real secret to the efficiency of heat pumps. They’re taking already existing heat and using it, as opposed to burning fuel to produce heat. As a result, heat pumps use a fraction of the energy that conventional heating systems do but produce comparable levels of indoor heating performance.
How Heat Pumps Work
By now, you’re probably wondering where a heat pump finds heat to capture in the middle of winter when you need heating indoors. To understand that, however, you need to first know that we humans aren’t great at perceiving the presence of heat energy in the air. For most of us, when the outside temperature drops into the 50-degree range or lower, we start feeling cold.
That feeling, though, is exactly that. There’s still heat energy in the outside air at those temperatures. There’s heat energy in the air all the way down to absolute zero, which is equivalent to -459.67 degrees Fahrenheit. Heat pumps can capture heat energy from the outside air, even when we can’t tell that there’s any heat there ourselves.
The way that heat pumps capture heat relies on fascinating scientific principles. The first is that heat always flows spontaneously from a hot to a cold body. It’s the second law of thermodynamics, and it’s also why ice cubes melt in the summertime instead of remaining frozen. A heat pump takes advantage of that by using a refrigerant that’s always colder than the outdoor temperature at any given time. As the refrigerant passes through a heat exchanger in the heat pump’s outdoor unit, the heat energy in the outside air naturally flows to it, warming it up.
Then, the heat pump’s outdoor unit passes the warmed refrigerant through a compressor. The compressor increases the refrigerant’s pressure until it turns from a liquid into a gas. Due to the chemical nature of the refrigerant, this has the side-effect of making the refrigerant many times hotter than it was in liquid form. In that way, the heat pump amplifies the heat energy absorbed from the outside air so that it’s sufficient to heat your house.
If this process sounds familiar to you, it should. It’s exactly the same way that your refrigerator works, except in reverse. In this case, though, you’re removing heat from the outside and venting it to the inside instead.
Are Heat Pumps Efficient at All Temperatures?
As you may have guessed by now, the lower the outdoor temperature, the less efficient a heat pump gets. The reason is simple. If there’s less heat energy available in the air, then the heat pump must run longer to capture enough to heat the building it serves. Eventually, if the outdoor temperature drops low enough, a heat pump may not be able to capture enough heat to maintain the desired indoor temperature of the building.
The average heat pump on the market today will remain more efficient than even the best available conventional system, down to approximately 25 degrees Fahrenheit. Fortunately, here in southern California, we don’t see too many days that even get close to that low a temperature. Plus, the technology that makes heat pumps work continues to improve. There are already heat pump models that retain their efficiency down to 0 degrees Fahrenheit for buildings in colder climates.
What Happens When a Heat Pump Can’t Produce Enough Heat?
Although heat pump owners here in southern California don’t have to worry too much about not having enough heat in the winter, it’s worth discussing how heat pumps handle such situations. Most heat pumps include a small auxiliary electric resistance heater that engages when the outdoor temperature drops too low for efficient operation. That helps to make sure that buildings with heat pumps never have to worry about a lack of heat, no matter how cold it gets outside.
However, the efficiency of a heat pump declines sharply whenever it has to engage its auxiliary heat mode. Plus, since electricity is typically more expensive than a fuel like natural gas, this can lead to much higher operating costs. Again, some manufacturers solve this problem by offering heat pumps with auxiliary natural gas burners, which help keep operating costs much lower in colder climates.
Consult the Heat Pump Experts
It should be obvious by now that the team here at We Care Plumbing, Heating & Air knows quite a bit about heat pumps. Hopefully, you’ve found this explanation of heat pump efficiency enlightening, too. If you have and you want to know more, We Care Plumbing, Heating & Air stands ready to help. We offer comprehensive heating, cooling, and plumbing services to homeowners across the Temecula, Murrieta, and Orange areas. For over 20 years, we’ve worked hard to be the go-to home services company in southern California. That includes becoming experts in emerging technologies like heat pumps. If you’re ready to find out if a heat pump is the right heating solution for your home, call We Care Plumbing, Heating & Air today!