A year ago I bit the bullet and replaced my 11 or so yr old combi boiler with a new highly efficient condenser combi boiler. At a cost of about £2.5k including lots of faff to get a drain in etc...
My old one was on its last legs, needed an expensive repair and the new one was 20% more efficient.
So especially after a mild winter I would expect my gas usage (in kW) for a year to be at least 20% less ....especially as I am constantly improving our insulation/draught proofing...and trying to save energy.
Nope - it is 7% less and actually about 7% more than the year before that... so I would say about the same.
I used to love combi boilers - endless amounts of hot water when you needed it, no tank to run out.
Except my last boiler was a PIA the water took ages to get start- then if you turn off the tap (to save water) and turn it on again you get cold water whilst it decides to heat it up again. I thought it was because it was on its last legs - but I use a newish condenser boiler somewhere else and have the same problem -maybe it has a long pipe run or something? Nope my new combi is just as bad...dishwasher broken so hand washing up -I'm rinsing in cold water as things are rinsed by the time it is warm. Quick hand wash -also just getting warm as you finish rinsing...
I think they only use less energy cos it takes so long for the water to get hot you give up and hardly use any hot water!
These new boilers last 10 yrs or so before they end up binned and are so complicated they develop lots of faults.
My dad has a boiler with a hot water tank - he replaced his 30 yr old one about 6 yrs ago (for a condenser but still with a tank) - couldn't get the parts any more for his old one and thought it would be more energy efficient.
In those 30yrs it broke down/needed repairing 3 times...his new one has had 3 repairs already...last time he was told it was getting on a bit now...
And his energy bills didn't go down noticeably...
So AIBU to think this is all a big con? They aren't really environmentally friendly - waste lots of water, more manufacturing and actually don't save you money - I've been tempted to boil a kettle to heat water rather than wait for the boiler to heat water for a bowl...