Quilt sent an over-the-air software update activating heat pumps that had been installed in a few customers’ homes for months, with both cooling and heating capacity up by over 20 percent — no new hardware involved. That’s an increase of 19,700 to 24,000 BTU per hour for cooling and some 20,500 to 25,200 BTUs per hour for heating —capacity you can feel in harsher weather right away without any corresponding change in efficiency numbers.
How software freed up extra space
For the most part, residential heating and air-conditioning systems are put in, turned on, forgotten about until they break. Quilt went a different direction, stuffing in more sensors than typically found on home systems — more pressure transducers, even-more-precise temperature probes, and tighter current sensing — alongside always-on connectivity. That treasure trove of data allowed engineers to map out thermal and electrical headroom not being tapped by conventional control strategies.
With that information in hand, Quilt’s team reprogrammed the control algorithms around such variables as compressor speed, the response of an electronic expansion valve, fan curves, defrost logic and current limits. The company sent new firmware to the microcontrollers in the indoor and outdoor units, and updated its supervisory software running on the main processor after rigorous laboratory checks on in-house rigs. The outcome: more output in the same hardware envelope, while remaining inside the compressor’s safe operating map.
Its development was overseen by thermal engineer Isaac McQuillen, who had previously directed cabin and battery thermal systems at an electric automaker. Many coworkers previously worked at Nest, Google, Apple, and Tesla — careers that regularly rely on entity updates — something that remains rare in HVAC.
Real homes, why it matters
The choice was at the request of installers and homeowners, Bothner said, in part because people were looking for a larger peak output in their large living rooms and open floor plans where there is one indoor head trying to reach across space. The extra capacity increases the comfort envelope, allowing for systems to more easily maintain setpoints when confronted by heat waves and cold snaps. In cooler locations, more heat output can delay or lessen the need for electric resistance backup (an expensive fuel source to operate).
The gains don’t affect rated efficiency—think SEER2 and HSPF2—but they do affect what the system is capable of handling. Under Air-Conditioning, Heating and Refrigeration Institute test protocols, capacity ratings indicate how much heat a system can move under prescribed conditions; Quilt’s numbers now classify its units in a higher class of real-world performance at the extremes.
The timing is in line with broader market trends. Space heating and cooling represent about 40% of residential energy consumption in the U.S., but heat pump use is steadily growing as states and utilities push for electrification, according to the U.S. Energy Information Administration. In a report on the role of heat pumps in decarbonizing buildings, the International Energy Agency described them as a “central technology”; enabling more from what’s already on people’s walls is simply espying that case.
What changed under the hood
The update basically allows the system to operate closer to the capacity while keeping an eye on itself. By looking at evaporator and condenser approach temperatures, real-time pressure ratios, the controller can safely prod compressor speeds upward, and fine-tune expansion valve positions to maintain better superheat control, to adjust fan speeds to avoid coil icing or discharge temperatures that are over-the-top. Current sensing is tight enough not to overdraw on peak, and should any parameters drift then the software falls back to conservative settings.
This approach, known as “software-defined HVAC,” has a parallel in something the auto industry refers to as software-defined vehicles. Just as carmakers offer post-sale improvements — faster acceleration, longer range, smarter thermal management — Quilt uses code to improve comfort, capacity and reliability throughout a deployed fleet.
The price and payoff of sensor-rich design
Over-the-air changes don’t just occur, either. Quilt overinvested in sensors, networking and compute relative to the amount a bare-bones system required. Executives concede that the bill of materials is slightly higher, but when those components unleash better performance, remote diagnostics and fleet-wide learnings that lead to fewer truck rolls and therefore more satisfied customers; the economics pencil out.
Industry experts said an OTA capacity upgrade over an installed residential heat pump was unheard of, if not a first. It’s going to establish a standard in an industry that has been able to manage firmware risk by having no-firmware at all. The opposite edge, of course, is responsibility: any change must maintain safety and certifications; it should also have rollback paths that get turned on when you use them without asking the guy who wrote the check; and ideally it’s something incrementally clear to installers (and customers), in so far as possible.
A sign for the HVAC industry
For manufacturers, this playbook could mean needing fewer hardware variants to accommodate various room sizes and climates. Instead of developing a new model to accommodate incremental capacity, one platform can stretch by software, streamlining inventory and installation. For the grid, software-tunable HVAC serves as a bridge to smarter demand response and peak load management — areas that utilities and regulators such as the California Energy Commission and even national labs have been touting.
When it comes to efficiency, heat pumps are already kicking butt. With this update, Quilt is trying to make the case that it can win on flexibility too — demonstrating that there’s some truth in a statement like, “The hardware you have at home doesn’t just get better when a technician shows up with a wrench.”