Many thermostats have been updated to support the running of heat pumps, including Evohome. Heatpump support is important to get maximum savings. Generally speaking, heat pumps are at their best when running at lower temperatures for longer to heat your house; they can be set to use more energy to heat water to higher temperatures to increase heating times. A smart thermostat needs to understand both the system it's connected to and how you want it to run, so you can choose between the best savings or the quickest heating times. If you're getting a heat pump, then make sure you buy a smart thermostat or heating system that is compatible with it.