Keeping cool with heat pumps
“Heat pump”—the name alone can cause confusion, because a heat pump is first and foremost an energy efficient air conditioner (AC). In fact, heat pumps and ACs cool the same way: by using electrical energy to move heat from inside to the outdoors. But a heat pump has a switch that lets you change its function from cooling to heating in winter—all with the press of a remote control button. And it’s far more efficient for cooling, using less than 50% of the energy of a typical window AC unit.
Heat pumps extract heat from (and move it to) different sources: air, water, or ground. A ductless air source heat pump (a.k.a. mini-split heat pump) are the most common type in homes and small businesses—though if you have existing ductwork, a ducted system is an option.
“Mini” refers to the system’s small size—and “split” tells you it’s made up of two distinct parts: an indoor air-handling unit and an outdoor compressor unit. The term “multi-split” or “multi-zone” describes a system with multiple indoor heat pump units connected to one outdoor compressor.
Unlike central AC, a heat pump’s outdoor condenser coil can switch roles, acting as an evaporator when in heating mode. The heat pump’s indoor unit holds the electronics that allow it to switch from cooling to heating, while a “line set” running between the two units houses refrigerant tubing and electrical wiring.
Both ACs and heat pumps use electricity to cool, but heat pumps are much more efficient—which means real savings for homes and businesses that choose to cool. They’re also highly efficient for heating: You can save if you switch from fuel oil, kerosene, propane, or electric resistance (individual saving will vary based on types of fuel being displaced and current fuel prices). If you currently use natural gas, wood, or pellets, a heat pump may not lower your bills—because the low cost of those fuels can offset the efficiency gains of a heat pump.
Another benefit to heat pumps is their compatibility with solar and wind power. For Vermonters looking to move away from fossil fuels, heat pumps may be a way to help get there.
EER, SEER, HSPF, COP—each one measures energy efficiency in a different way, so it’s not always easy to compare heat pumps with other systems. The bottom line: It’s safe to assume that heat pumps are more efficient than other systems for both heating and cooling, with the caveat that heating efficiency doesn’t always equate to savings. When comparing among heat pump models, look for a higher HSPF (more efficient heating) and a higher SEER (more efficient cooling). If you choose one that qualifies for an Efficiency Vermont rebate, you can rest assured that it’s been vetted for energy efficiency.
Each has pros and cons, but heat pumps enjoy some notable advantages over central and window air conditioning. The biggest is that you can cool and heat with one system, though a backup heating source is still recommended for the coldest of Vermont winter days. Heat pumps are professionally installed once, so you don’t have to remove or reinstall them seasonally. They need just a three-inch hole in the wall for the line-set, which means better security compared with window units that leave your home vulnerable. And they have no ducting to install and keep clean, as with central AC.
More key benefits:
- Quiet operation
- Zone cooling and heating
- No ducting required
- Flexible placement of outdoor unit: easy to keep out of view
- Modern, low-profile appearance
Besides needing a backup heating system on the coldest winter days, heat pumps come with other considerations. Consider your layout when weighing a purchase. A more open floor plan will be easier to cool or heat with a heat pump (and provide more savings) than a space with small/tight rooms. And be sure to carefully consider system size. If you size only for summer cooling, you may find the system can’t deliver the heating you need in winter. And, finally, while they typically lower your energy bills, the units themselves are expensive, about $4,000 apiece. Because they save energy, however, heat pumps do qualify for rebates and energy efficiency financing.