If you’ve searched for a smart thermostat, you’ve probably noticed that most buying guides treat all central heating systems the same way. No two systems are the same. A smart control that shaves a genuine amount off a gas boiler’s running costs might do very little for a heat pump — and in some cases, the wrong control can actually work against how a heat pump is designed to run.
This guide covers what’s different, what to look for depending on your system, and how the main options on the UK market compare.
Why the control matters more with a heat pump
A gas boiler is, at its simplest, an on/off device: it fires up, heats water to a set flow temperature, and shuts off when the room (or the water) reaches target. A basic thermostat calling for heat is a reasonable match for that behaviour.
A heat pump doesn’t work that way. It’s designed to run for longer periods at a lower, modulating output, adjusting its flow temperature to match outdoor conditions — a strategy called weather compensation. Efficiency (SCOP) is heavily dependent on keeping flow temperatures as low as possible for as long as possible, rather than cycling hard on and off. A control that treats a heat pump like a boiler — demanding full output, short bursts, and wide temperature swings — will often push flow temperatures higher than necessary and quietly erode the efficiency gains the heat pump was installed to deliver.
That’s the central distinction to keep in mind through the rest of this guide: boiler controls optimise for responsiveness; heat pump controls optimise for steady, low-temperature running.
The compatibility question: OpenTherm, eBUS, and proprietary protocols
Most modern boilers and heat pumps can accept “smart” controls“, but how they communicate with the appliance matters:
- OpenTherm is the most common open communication protocol, letting a compatible thermostat modulate boiler or heat pump output directly rather than simple on/off switching. Many heat pumps (and modern condensing boilers) support it.
- eBUS is used by some manufacturers (Vaillant among them) for similar two-way communication.
- Manufacturer-proprietary controls: The controllers that comes bundled with your heat pump (e.g., a Daikin Madoka, Mitsubishi Ecodan controller, or Vaillant sensoCOMFORT) are built specifically around that unit’s weather compensation curves and modulation range and tends to give the most reliable efficiency outcomes, at the cost of the smart-home features and apps that third-party thermostats offer.
- A thermostat that only provides basic on/off switching (no OpenTherm/eBUS support) will work with a heat pump but won’t let it modulate, meaning you lose one of the main efficiency levers a heat pump has.
If you have a heat pump, checking OpenTherm/eBUS compatibility before buying a third-party smart thermostat isn’t optional; it’s the difference between a control that helps and one that quietly costs you efficiency.
Comparison: smart heating controls by system compatibility
| Control | Boiler compatible | Heat pump compatible | Protocol | Notes |
|---|---|---|---|---|
| Honeywell Home (T6 / T4 / Evohome range) | Yes | Limited — check model | OpenTherm (select models) | Strong zoning via Evohome; heat pump support varies by model |
| tado° (Smart Thermostat X / Wireless) | Yes | Yes (OpenTherm system) | OpenTherm | Weather-compensation-aware modes on compatible systems; widely used, polished app |
| Hive | Yes | Limited | Mostly on/off; OpenTherm on some newer models | Popular and simple, but weaker fit for heat pump modulation |
| Drayton Wiser | Yes | Limited | OpenTherm (select hubs) | Strong multi-zone / TRV ecosystem |
| Danfoss Ally | Yes | Limited | Z-Wave (via hub) | Primarily a TRV/zoning ecosystem, not a boiler/HP replacement control |
| Vaillant sensoCOMFORT | No | Yes (Vaillant ASHPs) | eBUS | Manufacturer-native — closely tuned to Vaillant’s weather compensation curves |
| Daikin Madoka / Onecta app | No | Yes (Daikin ASHPs) | Proprietary | Manufacturer-native, good app-based scheduling and monitoring |
| Mitsubishi Ecodan controller (MELCloud) | No | Yes (Mitsubishi Ecodan) | Proprietary | Manufacturer-native; MELCloud gives remote access and monitoring |
Smart TRVs: useful, but the case is different for heat pumps
Smart thermostatic radiator valves (TRVs) — from Drayton Wiser, Honeywell Evohome, Hive, or Danfoss Ally — let you set room-by-room schedules and temperatures. For boiler systems, this is a fairly direct route to savings: heat only the rooms in use.
For heat pump systems, the case is more nuanced. Heat pump radiators are typically sized larger to work with lower flow temperatures, and heat pumps generally perform best running continuously at low output rather than being asked to ramp up and down as zones open and close.
Aggressive zoning that causes the heat pump to frequently modulate up to satisfy a newly opened zone can, in some setups, work against overall efficiency.
Smart TRVs still have a place for genuinely unused rooms, spare bedrooms, and so on, but the “close every door and zone everything” approach that suits a boiler doesn’t translate directly to a heat pump.
What to check before buying
- Confirm your system’s supported protocol (OpenTherm, eBUS, or none) before choosing a third-party thermostat.
- Check manufacturer warranty terms: some heat pump manufacturers specify that third-party controls must support their protocol correctly or that the manufacturer’s own controller is required to maintain warranty cover for certain features.
- Decide what you actually want: smart-home integration and a polished app (third-party options like Tado°), or the closest match to your heat pump’s designed weather compensation curve (manufacturer-native controller).
- For heat pumps, prioritise weather compensation support over zoning features; it has a bigger impact on running costs than room-by-room scheduling.
- For boiler systems, zoning and smart TRVs offer more straightforward savings, since a boiler’s on/off cycling doesn’t have the same sensitivity to frequent demand changes.
Which control suits your system?
- Have a gas or oil boiler? Want lower bills and better scheduling? A third-party smart thermostat with good zoning (Tado, Hive, Drayton Wiser) is a solid, low-risk upgrade
- Have a heat pump and want the best efficiency? Start with the manufacturer’s native controller, which is tuned to your unit’s compensation curve. Only look at third-party options if they explicitly support OpenTherm/eBUS modulation for your model.
- Have a heat pump and want smart-home features (app control, voice assistants, remote scheduling)? Check whether your manufacturer’s own app (MELCloud, Daikin Onecta, or Vaillant’s app) already covers this before adding a third-party layer that may reduce modulation control.
- Running a hybrid system (boiler + heat pump)? Compatibility gets more complex; a control that can manage bivalent switching between the two is a narrower category, generally best handled with the installer’s recommended system controller.
FAQs
Does a smart thermostat save more money with a heat pump or a boiler?
The savings mechanism is different. With a boiler, most savings come from better scheduling and not heating empty rooms. With a heat pump, the bigger lever is weather compensation — keeping flow temperature low and steady — which a basic on/off smart thermostat doesn’t address.
Can I use my existing smart thermostat when I switch from a boiler to a heat pump?
Possibly, if it supports OpenTherm or eBUS and your heat pump uses the same protocol — but check with your installer, since many heat pump installations are commissioned around the manufacturer’s own controller and compensation settings.
Are smart TRVs worth it with a heat pump?
They can be useful for genuinely unused rooms, but heavy zoning isn’t as universally beneficial as it is with a boiler, since heat pumps generally run best with steady, continuous low-level output rather than frequent demand changes.
What is weather compensation and why does it matter?
It’s a control strategy that adjusts the heating flow temperature automatically based on outdoor temperature, so the system runs at the lowest temperature needed to maintain comfort. It’s central to heat pump efficiency and increasingly used on modern condensing boilers too.
Final thoughts
The right smart control isn’t a single “best” product; it depends entirely on what’s heating your home. For a boiler, a third-party smart thermostat with good zoning is a no-brainer: it’s a well-understood upgrade with predictable savings. For a heat pump, the calculation is less about which app looks nicest and more about whether the control actually preserves the low, steady, weather-compensated running that makes a heat pump efficient in the first place.
If you’ve just had a heat pump installed, it’s worth resisting the urge to immediately layer on a flashy third-party thermostat before understanding what your manufacturer’s own controller is already doing. In many cases, the boring-looking bundled controller is quietly doing the most important job: matching flow temperature to outdoor conditions, better than a smart-home-branded alternative ever could. Where third-party controls do add real value on a heat pump is when they’re properly OpenTherm/eBUS-compatible and used to complement, not override, that compensation strategy.
As with most heating decisions, the good rule of thumb still holds: know what your system is trying to do, then pick the control that helps it do that, rather than the one with the best reviews on a general smart-home roundup.