When most people think about cooling their homes, they think of an air conditioner. Many cooling systems, however, are actually heat pumps. Many heating systems are heat pumps too. Confused yet? Don’t worry, that’s what we’re here for.
So what’s the difference? And why should you even care?
To answer the second question first, it can matter for the efficiency and cost of your heating and cooling system, both initially when you install it and during operation.
The former question requires us to dive into how both systems work, their similarities and differences. And it will lead us to when you’ll want to have one or the other in your home, and what some pros and cons are for both.
Why the Differences Matter
Both heat pumps and air conditioners cool your home, so does it matter which you have in your home?
It can, yes, and here are a couple of the biggest reasons that might be the case.
First, the type of system you have matters. By that, I mean electric or gas. Some homes have what’s known as a dual-fuel system, which merges electric and usually propane heating. But most of the time, your home will have a natural gas line or will be electric.
If you’re in an electric home, the time and cost to convert it to gas-fueled can be intimidating. Similarly, a home already equipped with a gas line is probably better served with a furnace for heating and an air conditioner for cooling. Exceptions do exist, though.
Heat pumps are also more common in warmer climates where they can provide moderate heating in the winter, but aren’t expected to endure long, bitter winters. The further north you go, the more you’ll see homes with furnaces and ACs instead of heat pumps.
Costs can vary as well, and while heat pumps are usually more expensive upfront because they can be used any time of the year, they can also be eligible for more discounts. Some states will have rebates for energy efficient heat pumps and not for air conditioners. The result can be a “cheaper” piece of equipment.
How Does an Air Conditioner Work?
Air conditioners don’t cool the air. Sounds counterintuitive, right? That’s ok; it’s a bit of a strange idea for a lot of people.
Think of it as heat transfer instead of adding cooling. This usually helps. To cool the air, it’s actually removing heat from inside and moving it outside.
Air circulates through your ducts and over an evaporator coil, which absorbs ambient heat in the air thanks to the system’s refrigerant. This refrigerant changes states from gas to liquid to either absorb or expel the heat, and it’s compressed outside to revert to its liquid state and expel the heat outside.
Then it’s just a matter of circulating the de-heated air back into your home, and repeating the process enough that it cools your home to the desired temperature.
How Does a Heat Pump Work?
This one’s going to be easier than the section above, because a heat pump operates almost exactly like an air conditioner. It just has a reversing valve so that it can remove heat from your home, or add heat from the outside air.
There’s more to it in practice, with intricate machinery that handles the reversing process and manages airflow, refrigerant and temperature both outside and inside. But the basic principles are the same.
Heat Pump Defrost Cycle
Heat pumps actually have a third operating mode: the defrost cycle.
When the unit is in heating mode, it’s possible for frost to form on the outdoor coil that collects heat from the outside air. This can become more of a problem depending on the relative humidity of the air.
To try to heat through this would cause the heat pump to work harder and less efficiently. The result would be higher bills and lowered lifespan of your heat pump.
To combat this, the unit can enter defrost mode. In this mode, the outdoor fan will shut off and the unit will pump heat into the outdoor coil, warming it up
During this phase, the heat pump is not heating your home. If your indoor fan is still running, this can result in lukewarm or even slightly cool air coming from the vents. This is normal.
This is also when electric coils in the air handler (or furnace if you’re using a dual fuel system) can also come in handy. The system can be set to activate the heat coils when the heat pump is in defrost mode. This way, you don’t sacrifice heat to your home for these stretches.
Often, this supplemental electric heat is more expensive than running the heat pump, but is why it’s often considered a secondary source of heat instead of the primary source.
Air-Source vs. Geothermal Heat Pumps
The type of heat pump we’ve been discussing so far is the air-source heat pump. Air-source systems pull heat from the surrounding air to pump in or out of a home.
Geothermal heat pumps work similarly. The only difference – though it’s a big one – is that the heat is transferred from the ground beneath your home. This can seem wild to some who aren’t familiar with this method, but it’s extremely energy efficient.
The issue is installation cost and maintenance. Most contractors aren’t licensed or trained in geothermal technology since it’s so rare, and so it’s exceedingly hard to find affordable options for installation and upkeep.
However, it’s important to know that they exist, and that heat transfer technology can be used to siphon heat from the earth around us, which is cool to think about and apply in useful ways!
Which is Better: Heat Pump or AC? Pros & Cons
There isn’t a single best answer here, but there are a lot of things to consider:
- Upfront Cost. Air conditioners tend to be less expensive initially compared to heat pump costs.
- Usage Rate. Will you get more use out of a heat pump year-round? If you live in a cold climate, it’s often better to have a dedicated furnace, which is usually paired with an air conditioner for maximum efficiency.
- Electric vs. Gas Power. If your home is already equipped for a gas furnace, with a working gas line, it may not make sense to convert to electric. Conversely, homes without access to gas lines will often have to pay a lot to install a working gas line to the home.
- Rebates and Tax Credits. Some federal and state programs offer incentives for heat pumps and other electrical home appliances. This can make heat pumps more attractive when you qualify.
Apples to apples comparisons on things like brand, efficiency, and expected lifespan are also relevant, but generally speaking, you’ll be able to find a range of both air conditioners and heat pumps that meet your energy efficiency needs and have a long expected lifespan.
The decision of which is better for you may become obvious as you analyze these factors. Other times, you’ll need to speak with a trained HVAC specialist to dig into the details a bit more, get quotes on systems, and figure out which is the better fit.
If you live in the Sacramento area, we hope CABS is your first call. We look forward to serving you for years to come!
