Winter heating, which is the bigger story for a lot of customers once they have lived with it for a year. Bosch Climate units in heat-pump mode deliver around 4 to 5 kWh of useful heat for every 1 kWh of electricity consumed. Combined with battery-shifted off-peak electricity at 7p per kWh, your heating cost in the rooms with AC drops to roughly 1.4 to 1.75p per kWh of heat. Cheaper than mains gas, oil, LPG, and very significantly cheaper than direct electric heating.
For some customers (typically smaller homes, or larger homes where only one or two rooms need to be kept warm during the day) AC in heat-pump mode is becoming a viable alternative to a full ASHP install. Lower upfront cost, faster install, same low running cost on smart tariffs. Not the right answer for every house, but the right answer for some.