I think its summit to do with new building regulations stipulating that every new home must have a certain percentage of its energy usage generated from it's own renewable energy source (in this case solar power). It's quite possibly an EU law now.
The system in my flat uses it for hot water and heating, and any excess power generated in summer goes through the normal electric. But it still has a gas boiler which kicks in automatically when demand outstrips the amount the flats solar panels can provide.
I have had the gas bolier set to off though, which means it is permenantly off and not had any shortage of hot water as yet. As for heating, well the new regulations for insulation means my flat is A-rated energy efficient, so it basically does not lose much heat it generates at all, not needed the heating on since I got the keys last Friday as the flats always around 20 - 22 degrees no matter how cool it is outside.
The solar power system is "intelligent" though, if it detects a possible shortage in energy, instead of relying solely on the backup gas boiler, it will lower the target hot water temp to comprimise and avoid using the gas bolier (you can set your target temperature range and turn off the intelligent boiling etc) and things like that, so pretty good. It also "learns" what you general usage pattern is, and if you allow it to, it will adjust how much energy it uses to heat the water at certain times of day/days of the week if it predicts a shortage of energy to sustain the target temperature, say it sees normally extremely low use between the hours of 2am and 7am, it will cease to heat to target between these hours etc... Everything can however, be overridden, so you have full control.
Just imagine what they will be like in 10 years time, the regulations get stricter and more demanding on efficiency and renewable energy each year!