At Caledonian Mechanical, we get a lot of questions about all-electric heat pump systems—split systems, rooftop packages, and everything in between. Over the years, we’ve installed and serviced dozens of heat pumps, and they’ve become a major focus for us. In this blog, I want to share what works (and what doesn’t) in heat pump applications, and why we lean heavily into Bosch heat pumps.
What Is a Heat Pump “Split System” or Packaged Heat Pump?
In simple terms, a heat pump does what an HVAC system does, but in both directions: it heats in winter and cools in summer, all using electricity—no gas required. A split system separates the indoor air handler and the outdoor condenser, connected by refrigerant lines. A rooftop package unit puts all that hardware (compressor, coil, blower) in one compact unit on the roof.
With modern systems rated from 15 SEER (modest efficiency) up to ~20 SEER (premium efficiency), heat pumps have become far more practical than they were even a decade ago, especially when paired with solar power or efficient electrical rates.
Why We Trust Bosch—and How They Stay Ahead
We’ve chosen to be Bosch dealers for heat pumps for very good reasons:
- Inverter (DC) technologies: Bosch adopted inverter compressor systems early in the U.S. market. Instead of always running at full capacity on or off, Bosch heat pumps vary their output gradually. On mild days, the system runs at lower capacity and adjusts up smoothly. That saves a lot of kWhs (electric usage) and reduces strain on the equipment.
- Dual-voltage indoor units: One clever Bosch feature is the option for air handlers that run on 115V rather than always demanding 230V. In existing homes where 230V wiring is challenging or unavailable, this flexibility is a game-changer.
- Longevity and quality: In our experience, Bosch heat pumps tend to last longer with fewer major failures compared to cheaper brands. Their parts availability, engineering, and support make them a safer bet for both us and the homeowner.
Because Bosch invested early in inverter-driven systems, they’re now in big demand—especially in markets like California where efficiency, clean power, and rebates matter.
The Efficiency Advantage: Why Inverter Heat Pumps Win
The key differentiator with inverter systems is the ability to modulate. On a 95°F summer day, your home doesn’t always need exactly 36,000 BTUs. Sometimes 24,000 or even 18,000 is enough. With a traditional “on/off” compressor, you either get everything or nothing—leading to excess power draw, short cycling, or stress on components.
But an inverter heat pump scales its output to match demand.
That smooth scaling:
- Reduces peak load (less spike in power usage)
- Saves energy by not overcooling or overheating
- Avoids internal strain like slugging (liquid refrigerant damaging the compressor)
- Helps maintain better humidity and comfort
The Pitfalls & Why Many Installations Go Wrong
We’ve seen plenty of heat pump installs that underperform, and usually, it traces back to two common mistakes:
1. Poor duct design / undersized ducts
A heat pump is less forgiving of high static pressure (air resistance in ducts) than a gas furnace. If your ductwork is tight or undersized, pressures above ~0.4 inches water column are going to cause performance issues. The system can struggle to push air, and the unit may cycle rapidly, triggering defrosts or shutdowns.
I’ve lost bids because a customer was told, “You don’t need to upgrade ductwork.” But six months later, they call me complaining their heat came on and off—exactly what happens when the air can’t flow through.
2. Lack of proper system design and controls integration
Heat pumps require specific controls: at least two stages, properly matched thermostats, zone control boards if you're doing zoning, and good surge protection. If those aren’t done right, the system either short-cycles or doesn’t heat/cool evenly.
Also, if you don’t commission (test and balance) the system—checking refrigerant charge, airflow in different modes, and each stage—you’ll never get the full benefit from the heat pump.
What We Always Do at Caledonian
When we design and install heat pump systems, we follow a checklist that protects performance and longevity:
- Load calculation & equipment sizing
We never oversell or undersize too aggressively. The unit must be capable of handling your hottest/coldest day while still modulating. - Duct evaluation and sizing
If ducts can’t handle the airflow demands, we upgrade them. Proper sizing keeps static pressure low. - Bypass or relief dampers (if zoning)
When some zones are closed, the system needs a path for excess air (either bypass or relief) so static pressure doesn’t skyrocket. - Surge protection on all critical electronics
With all the sensitive circuit boards and controls, adding surge protection is non-negotiable in our installs. Brownouts, blackouts, and lightning surges happen. - Multistage thermostats & controls
We use properly rated thermostats (Bosch or compatible) that support multiple stages and zone control, integrating with the system’s logic. - Full commissioning in all modes
We check performance in single zone operations, full load, part-load, heating, cooling—everything. We measure amp draws, temperature splits, airflow, and refrigerant pressures. - Ongoing maintenance
Even the best heat pump needs care. We schedule tune-ups, coil cleaning, filter changes, and performance checks—so it stays efficient and reliable.
Should You Replace, Or Just Fix?
Because many homes still use older furnace/A/C systems, heat pumps present a great upgrade—especially if you already have 240V wiring. But with older systems, sometimes the cost to retrofit ducts, upgrade controls, or fix low-voltage wiring pushes the economics closer to replacement.
When we quote a heat pump replacement, we always compare “fix what you have vs replace and upgrade.” And often, replacing with inverter technology is better long-term financially and performance-wise.
If you’re considering a heat pump upgrade or want us to evaluate your current performance, drop us a message. We’ll walk you through options (15 SEER, 18 SEER, 20 SEER or more) and help choose what fits your home, climate, and budget.