AReCoS
U.S. Patent 12,768,557

For decades, frost has stopped heat pumps from heating. AReCoS heat pumps are designed not to.

Designed to keep heating through frost without backup heat down to 0 °F (−18 °C). One controller in each unit is designed to set the whole machine at once, with no cloud in the control path. Rooftop units up to 10 tons first, then a 5-ton home size.

Reserve a place in the first units See the rooftop unit Read the AReCoS story

Free · no deposit · no commitment · pilot costs planned to be mostly covered for the first sites.

Controller: U.S. Patent 12,768,557, being tested with Oak Ridge National Laboratory, managed by UT-Battelle, LLC, under a research agreement (CRADA) supported by the U.S. Department of Energy · Air–water heat exchanger: patent pending · Rooftop unit: in design, chamber tests before 2027 pilots

One rooftop unit for every season A rooftop unit on a low commercial building, designed to send cool air into the building in summer and warm air in winter. Inside it, the AReCoS air–water heat exchanger, designed to keep frost to a thin, cleared layer, sits beside the embedded controller. Its water loop is a closed circuit; two connections on its side are where a ground loop can be added later, drawn as a dashed loop into the ground. Its embedded controller is designed to answer grid requests passed through the building's automation system, shown as a dashed line to the building. COOL AIR WARM AIR Embedded controller Rooftop unit Air–water heat exchanger DESIGNED TO KEEP FROST THIN Grid signal WATER LOOP Ground loop later Summer → cool air Winter → warm air

The AReCoS rooftop unit: one unit for summer and winter.

What defrost costs a conventional unit Heat delivered to a building over time. A conventional air-source unit loses output as frost builds and then stops heating briefly during each defrost, twice in the period shown. A dashed line holds near full output without the interruptions: what the AReCoS air–water heat exchanger is designed to deliver. AReCoS HEAT EXCHANGER A CONVENTIONAL UNIT 0 50 100% DEFROST DEFROST HATCHED: HEAT FROM BACKUP, NOT FROM THE HEAT PUMP time heat into the building
Illustrative. What defrost costs on a winter day. The heat pump runs in reverse to melt the frost, taking heat from the building, and gas or electric backup covers the gap. The AReCoS unit is designed to keep heating without that down to 0 °F (−18 °C), and to hold at least 70% of its 47 °F rated heating capacity at −15 °F (−26 °C).

Commercial or industrial refrigeration? The AReCoS controller is available for evaluation today

Watch

See how it works in 60 seconds.

Heat designed to stay on through frost, a controller in each unit, and units designed to share the load among themselves. Illustrated explainer with captions. Prototype design · certification planned. Watch the full two-minute version.

What is different

One controller, designed to optimize the whole unit and set every actuator at once.

It is designed to run a physics model of the whole refrigerant cycle on the unit itself. No cloud.

Patent pending

Hardware

Air–water heat exchanger, designed to keep frost thin while it heats

More about the air–water heat exchanger

How it clears frost. Details under NDA: request the technical brief. U.S. provisional application on file. U.S. Patent 12,768,557 is on the controller, not this heat exchanger.

Patent issued

Controller

Embedded controller, designed to set every actuator together

U.S. Patent 12,768,557, issued October 20, 2026, from application 18/592,624. Its hardware test is published in US 2024/0295337 A1 (FIGS. 4–7).

The full record The patent at the USPTO

More on how the controller works

In the architecture of U.S. Patent 12,768,557, the controller is designed to estimate the states its sensors can't measure and to set the actuators together in real time.

Startup, changeover and shutdown Winter, without defrost stops How it finds faults Does it need a supervisor? The controller in full

Three stacked time plots from the AReCoS heat pump model. Top: the compressor stops and, minutes later, restarts. Middle: the motor-driven reversing valve moves from heating to cooling while the unit is stopped. Bottom: the indoor and outdoor coil pressures come together while it is at rest, then separate the other way round when it restarts in cooling.
One changeover on a 59 °F (15 °C) day, from the AReCoS heat pump model: the motor-driven reversing valve moves while the unit is at rest, then it restarts in cooling. Amber: heating. Gray: stopped. Blue: cooling. Read it in full.

  • Optimizes itself, and answers the grid

    Designed to set the compressor, valves, fans and pump together for the lowest total power, and to shed or add load when the grid asks.

  • Units work together

    Designed to share the load and pick setpoints among themselves over BACnet, with no supervisory system.

  • Names the cause, not the symptom

    Designed to name the likely cause and where to look, in every mode.

Control stays in the building

No cloud in the control path. The AReCoS cloud only watches.

Designed to be safer than a cloud optimizer, and to do more.

Any command path from the internet, cloud or not, is a way in. AReCoS is designed to keep the optimizer, and every command, inside the units.

With a cloud optimizer

  • Setpoints changed from the internet
  • Units started and stopped remotely
  • A command path in from the internet
  • Cloud optimizing stops when the link drops
  • Moves setpoints, not how units run

With AReCoS

  • Every command designed to stay in the units
  • Cloud optional, and it only monitors
  • Designed with no command path from the internet
  • Designed to keep optimizing with the internet down
  • Designed to set every actuator together
Why: the 2026 supermarket attack, NIST and the EU Cyber Resilience Act

In October 2026, attackers remotely switched on defrost cycles in supermarket refrigeration controllers in France; about 700 supermarkets were affected, the French government said, and some stores threw away fresh and frozen food. No cloud service has been reported in that attack; the controllers were in the stores.

NIST warns that the risk of cyberattack on building controls increases significantly as they are joined to corporate networks and the cloud. What that means for your site.

Security and the ActWhy setpoints alone fall short

Sources: NIST, Tips & Tactics for Building Automation & Control System Cybersecurity, August 2026. Associated Press, Cyberattack targeting refrigeration systems hits 700 supermarkets, French government says, October 2026.

Heat pump products

What we're building

First the rooftop unit, up to 10 tons. Then a residential size, up to 5 tons. See the roadmap and dates, and how we make money.

Products

All-season heat pump RTU

Light commercial · up to 10 tons · ground-ready

Air source, with the AReCoS air–water heat exchanger (patent pending) and controller inside.

Prototype design, to be updated during certification

  • 22.1IEER
  • 13.4EER
  • 3.72COP at 47 °F
  • 2.57COP at 17 °F

10-ton unit.

Design basis

Show the design basis
  • WinterDesigned to hold 100% of its 47 °F rated heating capacity at 0 °F, and at least 70% at −15 °F.
  • Backup heatOptional electric, 10, 15 or 20 kW on the 10-ton unit; gas optional from 2028; pilots all-electric.
  • SummerDesigned to keep cooling up to 115 °F.
More of the design basis
  • ControlsBACnet or a standard thermostat · manual service mode. No cloud required.
  • Grid responseDesigned to hold a kW cap, shed 15% of its power on request or 40% in a critical event, or add 15%, winter and summer. The grid can ask; the controller decides how. How it works
  • DiagnosticsDesigned to track refrigerant charge in every mode, catch a bad sensor, and rank each fault with its likely cause. Catching a slow leak
  • Electrical208–230 V and 460 V three-phase, 575 V optional. Designed to fit a smaller circuit: backup is sized to the gap, not to defrost. Circuit sizes
  • RefrigerantR-454B (A2L, GWP 465 by EPA’s method), with leak detection and mitigation. Refrigerant
  • StandardsDesigned for UL 60335-2-40 listing, AHRI 340/360 ratings and ASHRAE 90.1. Full list · Full contractor specification

Inside the unit

Show the winter and summer diagrams
Winter, heating: the pumped water–antifreeze loop in the air–water heat exchanger is active around the outdoor coil, which is the evaporator; hot refrigerant goes to the indoor coil. Winter: heating WATER–ANTIFREEZE LOOP ACTIVE OUTDOOR AIR AIR–WATER HEAT EXCHANGER Outdoor coil (evaporator) WATER PUMP ON T AMBIENT Compressor Indoor coil (condenser) EXV P, T P, T WARM AIR TO THE BUILDING Winter, heating: the pumped water–antifreeze loop in the air–water heat exchanger is active around the outdoor coil, which is the evaporator; hot refrigerant goes to the indoor coil.Outdoor air passes the air–water heat exchanger, where the water pump drives the water–antifreeze loop around the outdoor coil. Cold refrigerant goes from the outdoor coil to the compressor, and hot refrigerant from the compressor to the indoor coil, which warms the air to the building; it returns through the EXV to the outdoor coil. Sensors read the outdoor air temperature, and the refrigerant pressure and temperature entering the compressor and leaving the indoor coil. Winter: heating WATER–ANTIFREEZE LOOP ACTIVE OUTDOOR AIR AIR–WATER HEAT EXCHANGER Outdoor coil (evaporator) WATER PUMP ON T AMBIENT Compressor Indoor coil (condenser) EXV P, T P, T WARM AIR TO THE BUILDING Summer, cooling: hot refrigerant goes to the outdoor coil, which is the condenser, and rejects its heat through the water–antifreeze loop to the outdoor air; cold refrigerant goes to the indoor coil. Summer: cooling WATER–ANTIFREEZE LOOP ACTIVE OUTDOOR AIR AIR–WATER HEAT EXCHANGER Outdoor coil (condenser) WATER PUMP ON T AMBIENT Compressor Indoor coil (evaporator) EXV P, T P, T COOL AIR TO THE BUILDING Summer, cooling: hot refrigerant goes to the outdoor coil, which is the condenser, and rejects its heat through the water–antifreeze loop to the outdoor air; cold refrigerant goes to the indoor coil.Outdoor air passes the air–water heat exchanger, where the water pump drives the water–antifreeze loop around the outdoor coil. Hot refrigerant goes from the compressor to the outdoor coil, and through the EXV to the indoor coil, which cools the air to the building; cold refrigerant returns from the indoor coil to the compressor. Sensors read the outdoor air temperature, and the refrigerant pressure and temperature leaving the compressor and entering the indoor coil. Summer: cooling WATER–ANTIFREEZE LOOP ACTIVE OUTDOOR AIR AIR–WATER HEAT EXCHANGER Outdoor coil (condenser) WATER PUMP ON T AMBIENT Compressor Indoor coil (evaporator) EXV P, T P, T COOL AIR TO THE BUILDING
  • Hot refrigerant
  • Cold refrigerant
  • Water–antifreeze loop
  • Sensor
  • AReCoS embedded controller designed to set compressor · reversing valve · EXV · fan · blower · water pump together

In every season, heat moves between the outdoor air and the refrigerant through the water–antifreeze loop: air to loop to refrigerant when heating, the reverse when cooling.

More: sensors, actuators and the controller All-season heat pump rooftop unit, simplified schematic A rooftop unit with an outdoor side and an indoor side. Outdoors: the air–water heat exchanger, designed to keep frost to a thin, cleared layer (patent pending), the outdoor fan, the compressor and the reversing valve. Indoors: the indoor coil and blower. Outdoor air passes through the air–water heat exchanger and leaves the outdoor section; return air from the building enters the indoor section, passes the indoor coil and leaves as supply air, so the two airstreams are separate. An expansion valve joins the two sides. Pressure and temperature sensors on the refrigerant line at each coil, and outdoor-air and supply-air temperature sensors, feed the AReCoS embedded controller, which is designed to set the compressor, reversing valve, expansion valve, outdoor fan and blower together. The water–antifreeze loop and its pump, which the same controller sets, are drawn in the winter and summer diagrams above. OUTDOOR SIDE INDOOR SIDE Air–water heat exchanger DESIGNED TO KEEP FROST THIN PATENT PENDING Outdoor fan Compressor Reversing valve EXV Indoor coil and blower P, T P, T T T AReCoS embedded controller PATENTED REFRIGERANT SENSOR SIGNAL COMMAND All-season heat pump rooftop unit, simplified schematic A rooftop unit with an outdoor side and an indoor side, drawn one above the other. Outdoors: the air–water heat exchanger, designed to keep frost to a thin, cleared layer (patent pending), the outdoor fan, the compressor and the reversing valve. Indoors: the indoor coil and blower. Outdoor air passes through the air–water heat exchanger and leaves the outdoor section; return air from the building enters the indoor section, passes the indoor coil and leaves as supply air, so the two airstreams are separate. An expansion valve joins the two sides. Pressure and temperature sensors on the refrigerant line at each coil, and outdoor-air and supply-air temperature sensors, feed the AReCoS embedded controller, which is designed to set the compressor, reversing valve, expansion valve, outdoor fan and blower together. The water–antifreeze loop and its pump, which the same controller sets, are drawn in the winter and summer diagrams above. OUTDOOR SIDE INDOOR SIDE Air–water heat exchanger DESIGNED TO KEEP FROST THIN PATENT PENDING Outdoor fan Compressor Reversing valve EXV Indoor coil and blower P, T P, T T T AReCoS embedded controller PATENTED REFRIGERANT SENSOR SIGNAL COMMAND

Simplified. The controller is designed to read every sensor and set every actuator together.

Residential heat pump: air source first, ground loop later An outdoor heat pump unit beside a house draws heat from the outside air, with two refrigerant lines running to the house. A dashed pipe below the unit shows a ground loop that could be added later; the unit is designed to connect to it without being replaced. Same air–water heat exchanger as the rooftop unit First: air source Later: add a ground loop
Air today, a ground loop later, in under 90 seconds: an illustrated explainer with captions. Prototype design.

Residential heat pump, ground-ready

Up to 5 tons

The rooftop unit's platform in a home size.

Prototype design, to be updated during certification

  • 23.8SEER2
  • 10.9HSPF2

5-ton ducted split.

Residential design basis
  • WinterDesigned to keep heating through frost without conventional defrost stops, like the rooftop unit, and to hold at least 70% of its 47 °F rated heating capacity at 0 °F, with optional electric backup for the coldest hours. In a pilot, an existing gas furnace is planned to stay as a backup.
  • Grid and serviceDesigned for demand response through a connected thermostat or gateway, refrigerant tracking in every mode, and UL 60335-2-40 and AHRI 210/240. Grid requests · Catching a slow leak

First units

Reserve a place in the first units.

Targeting rooftop pilots in 2027, commercial units in 2028 and residential pilots in early 2028, planned to be built with established manufacturing partners. Sites in the UK, Europe and elsewhere abroad are welcome too (pilots outside the United States).

  • Pilot costs mostly covered. Planned for the first pilot sites, in reservation order (how).
  • Judged in public. Pilot data is planned to go live on heatpumpmonitor.org, for anyone to check (how).
  • Priority for the first units. The list decides where they go.
  • First to hear pricing and schedules. Before anyone else.
  • Shape the first builds. Early sites help set configurations.

Owning, installing, warranty and verification: answers for owners, contractors and utilities.

Add details (optional)

No payment, no obligation. Your details are used only to plan the first units. Privacy.

Impact

What one unit is designed to save, and what a thousand add up to.

Estimates for a 10-ton rooftop unit heating and cooling a Minneapolis building, against a heat pump unit built to the federal minimum efficiency; not measured results.

  • 5,000–8,000 kWha year.
  • $650–1,050a year.
  • 2–3 t CO2ea year.

At scale: across a thousand units, about 5 to 8 million kWh, $0.65 to 1.05 million and 2,000 to 3,000 tonnes CO2e a year.

How the estimates were made

Energy: 3,000 to 5,000 kWh a year from higher efficiency and no defrost cycles, and 2,000 to 3,000 of backup resistance heat the unit is designed not to need. Cost: at about 13¢ per kWh, the 2025 U.S. commercial average, before any savings on demand charges.

Carbon: at the U.S. average grid intensity, and more where a gas furnace carries the cold hours today.

Scale: rooftop units cool nearly half of U.S. commercial floor space.

Method, and its update with measured data: How much carbon does a unit avoid? Sources: U.S. Energy Information Administration, Electric Power Monthly, Table 5.3; U.S. Department of Energy, Better Buildings, Key Considerations for Adopting Commercial Heat Pump Rooftop Units.

How we make money

The optimizer is designed in. For selected customers, we intend to share in the savings.

Unit sales, plus recurring revenue.

AReCoS is designed to put the optimization inside each unit.

Today, optimization can require

  • A supervisor in the equipment room
  • Add-on sensors and a gateway
  • Installation and integration
  • A cloud subscription every year

With AReCoS

  • An optimizer inside every unit
  • Units designed to agree over BACnet, with no optimizer above them
  • Optional performance-based savings agreement
  • Cloud optional, for monitoring only: it never commands
How AReCoS earns revenue
  1. Unit salesHeat pump rooftop units, then residential heat pumps.
  2. Share of savingsFor selected customers, verified against a measured baseline.
  3. Refrigeration controllerSupplied to operators; licensed per unit to manufacturers.
  4. Vehicle thermal systemsEV heat pump and controller for pilots; software licensed per vehicle for production.

Savings-share terms will be set with each pilot site. How each works, and whether it needs a supervisor. Utilities: ask about pilots.

Team

Ahmed Hussein, founder and CEO of AReCoS

Ahmed Hussein, PhD

Founder and CEO. He invented the AReCoS controller, U.S. Patent 12,768,557, and the air–water heat exchanger, patent pending. He spent twelve years designing controls in automotive and aerospace.

Background

His PhD is on unsteady flow and fluid–structure interaction, and he has built physics-based fluid-thermal models of electric-vehicle battery and cabin heating and cooling.

More · Google Scholar · LinkedIn

Ahmed Atallah, physics modeling lead at AReCoS

Ahmed Atallah, PhD

Physics modeling lead. A PhD in control from UC San Diego, he has worked with the founder since 2022, co-leading the physical models and control algorithms at AReCoS. He won the Best Paper Award at the 2019 AAS/AIAA Space Flight Mechanics Meeting.

Background

For ten years his work has covered physics-based modeling, estimation and optimal control: high-precision numerical integrators and orbit propagators, uncertainty quantification, nonlinear model predictive control, and sensor-fusion estimation for autonomous machines.

Google Scholar

Chief technology officer

Joining soon. A vice president from the automotive industry, to be named, brings 25 years of industrial leadership, 30+ global products, close to 40 patents, and a PhD in control engineering.

How it started: read the story, from a garage test bench to rooftop units.

Research collaboration: the AReCoS embedded controller is being tested under a Cooperative Research and Development Agreement (CRADA) with UT-Battelle, LLC, supported by the U.S. Department of Energy. UT-Battelle manages and operates Oak Ridge National Laboratory (ORNL) for the DOE.

Oak Ridge National Laboratory and the oak leaf symbol are registered trademarks of the U.S. Department of Energy. Use of this mark does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof or its contractors or subcontractors.

Investors: info@arecos.net

Roadmap

From a controller today to heat pumps for every season.

  1. Embedded controller for commercial and industrial refrigeration

    Available for evaluation, fitted to your system.

    Product brief

    Evaluation today

  2. All-season heat pump RTU

    Light commercial, up to 10 tons.

    See the rooftop unit

    Pilots 2027 · commercial 2028

  3. EV heat pump

    Heat pump and controller for pilots; control software licensed for production.

    EV heat pump

    Pilots summer–fall 2027

  4. Residential heat pump

    Up to 5 tons, on the same platform, ground-ready.

    See the residential heat pump

    Pilots early 2028

Dates after today are targets.

Let's talk.

Pilot sites for the AReCoS heat pump RTU, manufacturing partners for the first builds, the controller for your refrigeration system, or the EV heat pump for your vehicle program.

Email info@arecos.net
625 Kenmoor Ave SE, Suite 350
Grand Rapids, Michigan 49546