Gradient develops high-performance window heat pumps with variable-speed technology, offering an efficient path to low-carbon heating and cooling.
Gradient
Window Heat Pump
Easy-to-install 120V window heat pump using a standard outlet. Designed for extreme climates and quiet operation.
Description
Gradient’s high-efficiency, 120v window heat pump plugs into a standard socket and is designed for easy installation with residents in place, enabling heating and cooling electrification without drilling, plumbing, electrical upgrades, or major retrofits. The heat pump provides room-by-room temperature control, improving comfort by replacing centralized systems like boilers, with flexible, unitized HVAC. The system delivers efficient performance even in cold climates, helping reduce energy costs and emissions. Gradient’s design uses low-GWP refrigerant sealed at the factory, minimizing leak risk and eliminating the need for field refrigerant connections.
Use Cases
Electrify building heating and cooling
Install high-efficiency heating/cooling in building
Regulate indoor temperature by unit or zone
Improve tenant control over traditional central systems
Reduced risk of refrigerant leaks in a building/portfolio
Low barrier path to building HVAC electrification, no panel upgrades and easy to install
Key Differentiators
Minimally-disruptive, quick installation - Gradient's heat pump uses the existing hole in the building's envelope: the window. The mounting bracket requires no drilling or structural modifications. Installation does not require permitting. Built-in atomizers convert condensate into outdoor mist, eliminating plumbing and building alterations. No drainage is needed. Plugs into standard 120v outlet.
Efficiency in extreme temperatures - The heat pump system delivers efficient performance even in cold climates
Enhanced air quality - Optional MERV 13 filtration captures fine particulates and enhances indoor air quality.
Cost Savings
Gradient's pilot at NYCHA demonstrated up to 60% cost savings when compared to baseline steam radiators. ACEEE has published a report finding that, of the space heating decarbonization options for centrally heated multifamily buildings, window heat pumps generally have the lowest life-cycle capital and energy costs.
About
Decarbonization Impacts
Operational Emissions
Gradient units replaces low-efficiency fossil-fuel or electric-resistance heating with high-efficiency heat pumps and upgrades low-efficiency window AC units to models that use about 54% less energy. Moreover, room-to-room tenant controls allow residents to reduce unnecessary energy use.
Project + Building Compatibility
Project Type
Existing building retrofit
Essential Building Characteristics
Gradient’s All-Weather 120V unit can fit windows with a minimum width of 26”. Each window heat pump unit plugs into a standard 120V outlet within 6 feet of the installation (no electrical panel upgrades), and is designed to operate in most climates, from -13°F to 115°F.
Other required installation conditions:
Wall depth of 6.25 to 20 inches (measured from the inside window sill to the outside wall) to fit the mounting bracket.
Stable window and surrounding structure that can safely support the unit and bracket (total weight about 140 lbs).
Window that is at least 21 inches above the floor for safe installation.
Clear space around the outdoor side of the unit to ensure proper airflow; avoid spots blocked by walls, plants, or furniture.
Ideal Building Characteristics
Buildings which are master-metered (where the owner pays one utility bill for the whole building) or buildings that are fully tenant metered (where each unit has its own meter). Building wide WiFi preferred but not necessary.
Minimum Project Size
Minimum project size is a multifamily building (typically 5+ units).
Ideal Project Size
Preferred project size is larger buildings, i.e., 10+ dwelling units; dorms; manufactured housing; ADUs etc.
Additional Considerations
Gradient reccomends that their units are connected to WiFi to ensure that their customer service team can proactively monitor and address issues if they arise. Graident also offers a building management system for its fleet of units, Nexus, which enables building owners to monitor the energy usage and performance of their fleet on the back end. Nexus will also integrate demand response capabilities this year.
In spaces without a window, building owners could consider pairing window heat pumps with packaged terminal heat pumps, although this increases the amount of construction involved.
NY Contractor Availability
No specialized skills or tools are required for installation. Gradient is actively developing its qualified installer network conducting trainings with contractors who would like to learn how to install and service our equipment. Gradient will also train building maintenance staff on installation procedures and routine maintenance. See Gradient's installation manual for more info.
Other Screening Criteria
Gradient currently works directly with building owners to retrofit central heating and cooling systems with their window heat pumps. Eventually, Gradient heat pumps will be available in more traditional direct to consumer channels (i.e. Home Depot, Lowes, Costco, etc)
Example Installations
Installed By
New York City Housing Authority, Boston Housing Authority; Lynn Housing Authority; Providence Public Housing Authority
Case Studies
Boston is piloting window heat pumps in affordable housing
Resident Experience
During Installation
System takes about 30 minutes to an hour to install. Installation does not require any drilling or permanent alterations. This significantly reduces tenant disruption given the short installation time.
Post Installation
There are multiple ways for a tenant to use their Gradient heat pump. The onboard user interface (UI) allows users to change set point, mode, and fan speed directly on the unit. The unit also comes with a remote and an app. The app allows users to control the unit remotely and set schedules.
Financing
Upfront Costs
Gradient systems have an MSRP of $3,500, with bulk pricing available based on order volume and timing.
Ongoing Costs
Gradient's warranty includes 1-year parts & labor limited warranty: free repair or replacement of defective parts, including labor, through an authorized technician; Additional 4-year parts-only limited warranty: years 2-5 include free replacement of defective parts (labor not included)
Post-warranty costs: users should expect costs for filter replacements and routine maintenance.
NY Incentives/Financing Resources
CPC Climate Friendly Homes
Payback Period
Pay back periods depends on existing heating and cooling systems when estimating cost savings, and also on labor costs when determining O&M expenses. For example, Gradient window heat pumps are 4x more efficient than electric resistance heat and the New York City Housing Authority reduced their monthly bill by 60%.
Operations, Management, and Maintenance
Operations and Maintenance Requirements
Similar to most other HVAC units, the heat pump has an indoor air filter that must be cleaned periodically. The heat pump also has a condensate filter that requires periodic cleaning. Cleaning in both cases must be done following the instructions in the manual.
Ease of Operations
Like other heat pump systems, the Gradient Window Heat Pump involves a modest learning curve for residents. Gradient recommends a “set it and forget it” approach, consistent with best practices for heat pump operation. Early deployment data suggests some residents continue to use the system like a traditional window AC, turning it off or unplugging it when leaving the room, which reduces efficiency. Gradient is expanding tenant education efforts to encourage more effective, energy-efficient usage.
For building management, training and adoption are relatively straightforward. Installation is simple, typically completed in under an hour, and routine maintenance takes about 10 minutes per unit. Staff at early deployment sites have reported spending significantly less time on maintenance compared to legacy systems such as steam radiators.
Service Support
Gradient trains technicians to maintain systems; maintanance is similar to mini-split maintanance.
Units come with a 5-year standard warranty: first year covers parts and labor, and the following four years covers parts. Additional repairs can be done by a qualified Gradient technician.
Data + Performance
Gradient’s NEXUS platform is a building wide fleet management tool for multifamily owners and operators, housing authorities, campuses, and organizations; features include:
Smart Set Point Guardrails
Personalized Tenant Comfort
Lower Downtime with Proactive MaintenanceWeather & Usage based Load Forecasting
Demand Response Integration
Refrigerant Management
Factory-sealed low GWP R-32 refrigerant design reduces leakage by 89-95%, unlike traditional HVAC systems.
Future Proofing
Gradient’s window heat pump enhances building resilience by enabling a transition to fully electric heating and cooling, helping mitigate climate impacts. Its design supports more flexible energy use, allowing buildings to better adapt to changing grid conditions and increasing electrification. As the grid evolves, this flexibility becomes critical. Nexus, Gradient’s building management platform, builds on this by enabling demand response, helping shift energy use away from peak periods and further protecting residents from grid strain and outages.
Specifications
UL 60335-1; UL 60335-2-40; DOE CFR; ENERGY STAR Version 5.0; ENERGY STAR Most Efficient 2025; CEE Advanced Tier Certification
