We have a glow worm 24cxi thats old and needs replacing, we have a 3 bed semi with 7 good size rads. Having looked around we have decided on a Baxi combi. The question is do we go for the 24 duo or the 28? Are we going to get any benefit from the larger boiler when the 24 seems adequate. My theory is that the 28 would be doing less work as its more than man enough, or are we just wasting money and would we get bigger bills from having the bigger boiler.