These modern systems scale up and down

A heat pump prevents your house from getting too cold, or too hot. Maintaining one temperature setting uses less energy than altering the climate. Inverter driven heat pumps use minimal power to control indoor temperatures at your comfort level. The best heatpumps do this with 2 technologies:

1. Variable refrigerant flow (VRF) enables heat pumps to use only the amount of refrigerant they need to cool/heat the environment. Electronic expansion valves (EEVs) and multiple refrigerant circuits lets a 3-ton unit scale itself down to 1 ton.
   
2. Variable frequency drives (VFDs) are special motors that can operate at multiple different electrical voltages. Many of the best compressors and blowers have up to 70 “stages.” This permits the compressor to stage from 35% power to full capacity. 

Look for “Inverter Driven” or Energy Star Rated

VRF/VFD technology is often marketed on the term “Inverter Driven.” Another marking is Energy Star approved, or Energy Star rating. A basic heat pump is an air conditioner with a special reversing valve. Inverter Driven systems go way beyond and include smart technology crucial to achieving reliable efficiency.

A motor that operates at half capacity to keep you comfortable, also consumes less electricity. This is the beauty of inverter technology.

Why do Heat Pumps have a SEER range instead of one number?

All air conditioners lose capacity and efficiency as the temperature outdoors drops. The colder it becomes, the more electricity a heat pump will consume. However, in January of 2024 the Department of Energy made a big announcement: 8 major manufacturers completed the Cold Climate Heat Pump Challenge.

These special heat pumps can produce 100% of their rated heating capacity (measured in BTUs) at 5F. Cold climate units are marketed under terms like “Hyperformance” or “Hyperheat” and are slightly less efficient than southern climate heat pumps.

The easiest way to think about the sliding SEER scale is this: When it’s 100F outside you only need to drop the indoor temperature 20-25 degrees to achieve comfort. When it’s 0F you need to maintain the home 65-75 degrees different from the outdoors. Heating in winter simply takes 2x to 3x more energy. It’s going to be more expensive.

2 heat pump myths

• Heat pumps don’t heat well below 30F.

This hasn’t been true of modern inverter driven HVAC systems in a couple decades. Yes, the cheap, economy units use to heavily rely on electric resistive heaters when the temps dropped. The newer technology has matured. Now even the budget friendly Cold Climate units produce 88% of their overall BTUs at 5F, and approximately 60% at -22F. Norway leads the world in heat pump installations.

• Inverter driven heat pumps are highly complex, and short cycle in the summer.

The claim is partial true. Many units today are controlled with advanced printed circuit board controllers. Yet, even computerized they’re not that incredibly different from basic systems. They’re just smarter. The short cycling claim is bogus. If an inverter system isn’t dehumidifying sufficiently the installer is to blame. Some causes for this are:

1. The installer placed too large of a system for the house. Easy to do if a proper heat load assesssment wasn’t created for the house (Manual J).
2. The installer failed to customize the blower speed settings to achieve proper CFM air flow. This can be adjusted after the fact.
3. The installer sold you a regular heat pump, not an inverter driven heat pump. Unfortunately, mini split clones exist. It’s a disreputable technician who installs one. All heat pumps must be sized to heating needs of the house, and you always need more heating BTU’s than cooling BTU’s.