Our entire combi boiler range is rated energy efficiency class: a. A cylinder thermostat will be programmed to approximately sixty degrees celsius, and can sense if the water is already heated to the required temperature consequently, the tank will not come on if the hot water has not already been used that day. From £140 plus vat for most domestic properties. Ready to start shopping? let’s talk about how to choose the best boiler model for your home and budget. Asap plumbing installed.