NOX Energy, a residential energy management software startup based in Belgium, has closed a €3 million (USD $3.4 million) seed round to scale a platform that connects household energy assets — heat pumps, solar panels, batteries and electric vehicles — to wholesale energy markets across Europe.

Rise Proptech and Volve Capital co-led the round, with participation from Seeder Fund, Uneti Ventures, Fair Impact Fund and 100in.

The company, founded in 2024 by CEO Axelle Moortgat and COO Louis Clermont, develops smart energy management software that optimizes the operation of distributed home devices based on electricity prices, weather forecasts and grid conditions. The premise is straightforward: aggregating thousands of residential assets turns individual households into a tradable flexibility resource that energy suppliers and grid operators can call on.

The operating numbers behind the raise are still modest but growing. Over the past year, NOX has connected more than 10,000 energy devices and signed customers including Eneco and Frank Energie. That installed base sits almost entirely in Belgium and the Netherlands, the two markets where the company currently operates.

The new capital carries a clear geographic and product mandate. NOX will use the proceeds to expand beyond Belgium and the Netherlands into new European markets, according to the company. On the product side, the strategy shifts away from consumer acquisition and toward embedding the optimization layer directly into manufacturers' own applications — making flexibility management a built-in feature of the device, rather than asking households to download a separate energy-management app or install additional hardware.

That embedded route matters for the flexibility market's growth trajectory. Consumer adoption of standalone energy apps has historically been a bottleneck for virtual power plant and demand-response aggregation, with participation rates low outside enthusiast segments. If optimization ships inside the OEM app that a heat pump or battery owner already uses, the marginal cost of recruiting each flexible device approaches zero — and the addressable pool of controllable capacity expands accordingly.

Moortgat framed the company's position as infrastructure sitting between two sides that each need the other but cannot easily connect.

"Millions of homes already have a heat pump, battery or solar panels connected to their manufacturer's app," Moortgat said. "Energy suppliers and grid operators need the flexibility these devices can offer, but every manufacturer and every market works differently. NOX sits in between as the infrastructure of flex, connecting both sides."

The integration burden the CEO describes is real. Each device manufacturer exposes different APIs and control protocols, and each national market operates under its own balancing arrangements, tariff structures and grid-operator rules. A platform that abstracts both layers — device-level on one side, market-level on the other — removes the need for every supplier, aggregator or OEM to rebuild that connectivity from scratch in every jurisdiction.

For grid operators, the stakes are capacity-related. As electrification of heating and transport accelerates, distribution networks face peak-load constraints that would otherwise require conventional reinforcement. Flexible operation of heat pumps, EV chargers and home batteries can shave those peaks and defer or avoid grid investment — but only if the devices are actually orchestrated at scale. Software-mediated aggregation is the mechanism by which that distributed capacity becomes dispatchable.

NOX's expansion will run through a European market landscape where demand-side flexibility is moving from pilot projects toward procurement. Grid operators in the Netherlands and Belgium have been among the more active in contracting flexibility at distribution level, and the EU's electricity market design reforms push member states to enable demand response participation in wholesale and balancing markets — a regulatory tailwind for platforms monetizing residential device flexibility across borders.

What determines NOX's trajectory now is execution against two measurable milestones: the pace of market entries beyond Benelux, and the number of manufacturer integrations that move the company's model from optional consumer apps to default embedded capability. The €3 million gives roughly a seed-stage runway to prove both. Watch for OEM partnership announcements and new country launches as the indicators of whether the "infrastructure of flex" thesis converts installed devices into contracted grid capacity.