Our 3-bed house has gas central heating since 2007, and the programme controller has 3 time periods, with one-hour booster button. Getting fed up of coming into a cold house in the evenings at various times and switch on boiler for the system to come on. Was informed that if the system is left on through the day at a lower temperature, this would mean a warm house and more efficient for the boiler. Is there some truth in that - terrified of receiving a huge bill if the system is left on 24/7!? Pity the programme controller doesn't have hourly slots, so that the system would come on/off every hour through the day. Advice would be very much appreciated, thanks. Allencat3