New York’s prewar apartment blocks and Europe’s 19th‑century tenements share the same problem: beautiful architecture wrapped around fossil‑era plumbing. Boilers are dying, summers are hotter, and deep retrofits are expensive, slow and politically painful. That is why Gradient’s latest move matters beyond the US market.
By turning a clever window heat pump into a coordinated, software‑driven system for whole buildings and even the electric grid, the startup is quietly sketching a blueprint for how we might decarbonise legacy housing without tearing it apart. The idea will not stay in New York for long.
The news in brief
According to TechCrunch, US startup Gradient has introduced new software, called Nexus, for its horseshoe‑shaped window heat pumps. The hardware already replaces traditional window air conditioners and can both heat and cool without blocking the entire window.
The new Nexus layer links many individual units in multifamily buildings so that building managers can manage comfort and energy use across the whole property. Managers can set temperature guardrails to prevent excessive heating or cooling in buildings that often share a single electricity meter. TechCrunch reports that in one trial, capping the maximum heating setpoint around 26 degrees Celsius cut energy use by roughly a quarter in just one day.
Gradient is focusing on older buildings whose central boilers are reaching end of life, including public housing in New York City and affordable housing in California, and is in talks with universities for retrofitting dormitories. Because the units plug into existing outlets and do not require invasive construction, installations can be completed in hours. Nexus can also reduce current draw in buildings with fragile wiring and is being developed to participate in grid demand response, turning thousands of small heat pumps into a controllable resource during peak electricity demand.
Why this matters
The uncomfortable truth of climate policy is that our biggest problem is not futuristic glass towers; it is the stubborn, draughty, boiler‑fed buildings where most people actually live. In Europe and North America, the majority of residential square metres that will exist in 2050 are already standing today. Replacing every boiler with a central heat pump system, upgrading electrical panels, and reinsulating façades is technically ideal and politically unrealistic at the required speed.
Gradient’s approach attacks precisely that bottleneck. A window unit that can be dropped into an existing opening with minimal electrical hassle slashes the two scarcest resources in retrofits: time and disruption. For landlords and social‑housing authorities, a solution that can be deployed apartment by apartment, without evacuating residents or re‑plumbing risers, is far more deployable than a full‑blown mechanical overhaul.
The new Nexus software changes the business logic again. Instead of selling isolated appliances, Gradient is selling a controllable fleet. Building managers gain levers: they can avoid bill shock in master‑metered properties, enforce sensible comfort bands, and smooth demand spikes. Grid operators gain a demand‑response resource that can be modulated without switching off entire buildings.
Winners are obvious:
- Owners of ageing multifamily stock who suddenly have a path to partial decarbonisation at lower capex.
- Public‑sector landlords under pressure to provide cooling as heat waves worsen.
- Utilities that need flexible loads to balance intermittent renewables.
The losers? Gas utilities whose long‑lived boiler base becomes easier to bypass, and traditional HVAC vendors whose business models rely on high‑margin, centralised systems installed once per building, not hundreds of networked devices plus a software contract.
The deeper shift is that the value in climate tech is sliding from metal to code. A heat pump is hardware; a building‑wide orchestration layer is a recurring revenue stream and, potentially, a powerful lock‑in.
The bigger picture
Gradient’s Nexus move sits squarely in three overlapping trends.
First, the global heat pump boom. After years of being a niche climate nerd topic, heat pumps are now mainstream policy tools. Governments from Washington to Berlin are throwing subsidies at them because they electrify heat and pair well with cleaner grids. But large, centralised systems have run into practical barriers in dense, old housing: structural constraints, resident opposition, connection delays. Compact, window‑style units offer a way to dodge those frictions.
Second, buildings are becoming grid assets. Over the last few years, we have seen the rise of virtual power plants where batteries, EV chargers and thermostats are orchestrated to support the grid. Air conditioning has often been treated as a problem load that destabilises summer peaks. Gradient is trying to flip that narrative: if you know which flats face the shade, which façades have more thermal mass, and how quickly each room warms, you can shave demand in a targeted way without sacrificing comfort.
Third, software is becoming the differentiator in once‑commoditised hardware categories. Just as smart thermostats and EV chargers spawned whole flexibility and data‑analytics businesses, a heat pump that exposes rich telemetry and accepts remote control can plug into grid‑service markets, carbon‑optimised operation, and performance‑based financing. Traditional manufacturers who still treat connectivity as a checkbox feature will find themselves undercut by nimbler, software‑native players.
It is worth noting that this is not entirely unprecedented. Japanese and South Korean vendors have long sold highly networked heat pump systems, and European makers are rapidly adding demand‑response interfaces. The twist here is the pairing of a form factor purpose‑built for retrofit with software that explicitly targets both building‑level and grid‑level optimisation.
The European angle
Europe is, arguably, the ideal laboratory for this model. Around three‑quarters of EU buildings are considered energy‑inefficient, and most will still be standing in 2050. From Parisian Haussmann blocks to Berlin Altbau and Ljubljana or Zagreb post‑socialist towers, retrofits are complicated by heritage concerns, fragmented ownership and tight budgets.
EU policy is moving fast. The revised Energy Performance of Buildings Directive pushes member states towards phasing out fossil‑fuel boilers, while the Green Deal and REPowerEU plans explicitly call out heat pumps as a cornerstone technology. At the same time, the EU is building a regulatory framework for flexible demand through electricity market design reforms and national demand‑response schemes.
In that context, a product that does not require ripping out radiators or redesigning courtyards is politically attractive. Imagine a municipal housing company in Vienna or Barcelona able to roll out 500 plug‑in heat pumps over a summer, financed via operating budgets instead of capex‑heavy renovations, and then enrolling that fleet in a local flexibility market. That is the kind of hybrid public‑service and grid asset regulators in Brussels say they want, but the technology stack has been missing.
There are, of course, European twists. Tenant protection laws in countries like Germany or France limit how much control landlords can exert over indoor temperatures. Data protection under GDPR means that any telemetry Gradient‑style systems collect – room temperatures, usage patterns, even presence information – must be minimised, well secured and transparently governed. And European incumbents from Bosch to Vaillant, as well as a growing cohort of Nordic and Italian heat pump startups, will not cede this opportunity without a fight. Expect them to copy the orchestration logic, if not the exact window form factor.
For Central and Eastern Europe, where many district‑heated buildings already struggle with uneven comfort and underinvestment, the ability to add decentralised, smart cooling without grid‑overloading electric resistance heaters is particularly relevant.
Looking ahead
Gradient’s announcement is best read less as a product launch and more as a preview of where building electrification is heading.
In the next three to five years, expect every serious heat pump vendor to offer some variant of a cloud‑based management layer for multifamily and commercial buildings. Utilities and grid operators will increasingly make participation in flexibility programmes a condition for accessing the most generous rebates. The integration between building‑level control (what tenants feel) and system‑level needs (what the grid can supply) will tighten.
For European readers, there are a few key signals to watch:
- Do local manufacturers introduce truly retrofit‑friendly, room‑scale units, not just conventional monoblock and split systems with a wifi module tacked on?
- How do national regulators reconcile landlord control features with tenant rights and anti‑energy‑poverty safeguards?
- Will DSOs and TSOs move fast enough to create standard interfaces and remuneration schemes for small flexible loads, or will a patchwork of proprietary utility programmes slow deployment?
There are also real risks. Poorly designed guardrails could become a backdoor for pushing uncomfortable temperatures onto low‑income tenants in the name of saving money. Cybersecurity is not optional when thousands of controllable heating devices are sitting behind consumer routers. And if only high‑end or newly refurbished buildings get smart, flexible systems, while older stock remains locked into volatile fossil fuel prices, the social gap in comfort will widen.
Still, the direction of travel is clear. The most interesting climate tech for buildings will not be visible on glossy architectural renders. It will be the quiet, modular, software‑defined systems that slip into the messy reality of existing housing and slowly rewire how heat flows through our cities.
The bottom line
Gradient’s Nexus platform shows how much climate leverage sits at the intersection of humble appliances and smart coordination. By turning window heat pumps into a networked, controllable resource, the company is sketching a pragmatic path to decarbonising old buildings and supporting strained grids without waiting for grand renovations. The opportunity for Europe – with its ageing housing stock and aggressive climate goals – is enormous, but so are the governance and equity questions. The next step is ours: will regulators, utilities and manufacturers embrace this model, or cling to boiler‑era thinking until the next heat wave forces their hand?
