Hi all this is my first post. Have been lurking through the threads on Vaillant ecotec and Megaflo controls to find out how I can improve my systems efficiency as Gas bills around £1250pa. House is a detached five bedroom with two bathrooms both with showers and one also with a bath. Two years ago the existing three bedroom house which is brick built with cavity walls and timber suspended floors was extended on two floors with pitched roof to modern building regs. The existing has recently had cavity wall rockwool insulation blown in. A new unvented Vaillant ecotec plus 637 and Megaflo CL170HE was installed in loft space and wired up with a room stat, honeywell ST9400C programmer, two 2port valves all marshalled into a plastic junction box, also new water main installed. The boiler was set to 75deg C output temp Megaflo to 60degC and all works fine apart from the gas bill. I am looking for better efficiency from the system and try to get the boiler return temp down as low as practical so it can actually be a condensing boiler. What I've done recently to tune system: 1. Discovered from the IDHEE "Whole house heating method" the losses are about 17kW including nominal 2kW for DHW. 2. Reset max boiler output to 25kW. 3. Set boiler flow temp to 60degC. Just checked boiler temps and with outside 12degC and room stat hovering on 20degC the boiler flow is 57degC and return is 49degC with boiler firing. The DHW was originally on constant but now timed to come on for three half hr sessions per day, which is a bit marginal with boiler set at 60degC for reheat. Having read about the Vaillant VRC470 weather compensating programmer and VR65 I am trying to discover whether fitting these will enable the system to run more efficiently than present. I spoke to Vaillant about this but its all a bit uphill with them and they have no technical manuals available. One advantage apparently with vaillant controls the DHW reheat will improve as not be limited by the present 60degC flow temp. Should I get the Vaillant controls or not bother? Any comments gratefully received.