Dutch startup Ona has launched a €165 kit that turns an ordinary split air conditioner into a price-aware heater. The idea, described by IO+ on 29 October 2026, is simple: run the air conditioner in the afternoon when electricity is cheap, let the concrete walls, floors and ceilings soak up the heat, and coast through the expensive evening hours on what the house has stored. No water tank, no home battery.

Two boxes and an app

  • Energy Hub: plugs into the meter cupboard and reads how much power the home uses and produces. Over the internet it pulls electricity prices, weather forecasts and solar irradiance forecasts.
  • Airco Controller: a smart remote for the indoor split unit. Co-founder Alexander van der Linden calls it "a hack to make those devices smart", which suggests it talks to the unit the way its own remote would rather than through a manufacturer cloud.
  • App: the owner sets a comfortable temperature range, and the system only moves within it. The Hub learns how quickly each house loses heat and adjusts how early it starts pre-heating.

Ona says the kit is plug-and-play. It has been tested for more than a year in several homes, including a large late-1990s detached house and a corner terraced house. One couple relied on it all last winter after their gas boiler broke down.

The savings claim

Ona estimates an average saving of €275 a year for a terraced house compared with the same home without smart control. Half of that comes from steady automatic control, the other half from shifting heating and cooling into the cheapest hours. If the air conditioner also replaces the gas boiler for heating, the company puts savings at around €540 a year. Its online simulator covers 108 house setups, and Ona says none of them saved less than the price of the kit in the first year.

These are the company's own figures. How much heat a house keeps depends heavily on insulation, which the founders themselves point out. Co-founder Stefhan van der Kemp argues the gap is still large: the price difference between afternoon and evening "can easily be tenfold", especially in summer.

Why the Netherlands, and why now

Dutch net metering for solar panels ends on 1 January 2027, so midday solar power will be worth much less to the households that export it. Gas has gone the other way: Van der Kemp says a cubic metre cost about €1.20 when the team started and is now closer to €1.70-1.80. According to TNO research cited in the article, 19% of Dutch households, roughly 1.6 million, already heat with their air conditioner, but few of them use any smart control.

The three founders met at solar car maker Lightyear and started Ona in 2025. They are already working on an energy thermostat meant to become a central control point for the whole home's energy use.

What the announcement does not cover is just as relevant for smart home owners: there is no word on which air conditioner brands are supported, whether the Hub works without Ona's cloud, or whether it offers a local API or MQTT for Home Assistant and similar systems.