I did exactly the same as you are planning. Unfortunately the gas price increases put a damper on any noticeable savings. However, of course a new condensing boiler will be far more efficient than your older system, so savings can be made subject to . . . ..!
I have noticed an enormous reduction in my Gas bills- so much so that last year B-Gas at my request sent me a credit for £150, AND reduced my Direct Debit by about 30%.Of course I have yet to see how we have fared over this winter, as we have had the boiler on all day- when one is 80 years old one needs the warmth!
some of our customers have switched from old conventional heating systems with tanks and cylinders to condensing combis and seen their gas bills go up, mainly cos combi's burn much more gas esp on the hot water.
I understand during this last freeze, condensing boilers have stopped working because the steam relief condensing outlet has blocked with frozen water.
Vignon is right. Was in the plumbers merchant, after the cold snap, and a plumber was moaning about that problem. Said when customers called their Home emergency services out over Xmas, they just cut the drain pipe inside the property and stuck it in a bucket. Now real plumbers were having to sort it out. Make sure, if you have to have a drain tube run outside, it's insulated in some way.
i had a new boiler fitted last june and also new double panel radiators and the savings have been approx 30% which im very pleased with.the boiler is brilliant and its great having instant hot water rather than waiting ages for the tank to heat up.ive had no problems with it in the cold weather touch wood,im sure you will be pleased with yours.
We are in the process of having alterations done and part of that is replacing our 20 year old Baxi Bermuda back boiler, so I will be interested in this thread