Inefficient Central Heating Boilers

[Theland]

As a percentage, how efficient are CH boilers?
Given the vast amount of heat lost throughthe balanced flue, do the manufacturers not have additional kit to recover the lost heat?
Also, is such kit not fitted to the boilers as to do so would make the price prohibitive?
I am puzzled why such massive energy loss is not addressed by the government as a matter of urgency.
If we can put men on the moon, and work out and build a Large Hadron Collider, why can't we exhaust cool gasses from the flues on our central heating boilers?
I lose sleep over this.

[Hymie]

Condensing boilers attempt to capture some of this wasted energy, using it to pre-heat the water entering the boiler. In ideal operation, the water vapour created by the combustion of fuel gases condenses, thereby giving up the latent heat of vapourisation. However the water entering the condensation section of the boiler must be below 63°C for it to work. While a combi-boiler heating Direct Hot Water will meet this criteria, I doubt that my central heating return flow is less than this temperature; and therefore there will be no capture of energy through condensation.

My boiler has an output power level of 30kW, even if it has a 90% efficiency (which I doubt), 3kW is being lost. Personally, rather than using condensation to capture more of the energy, I think it would be better to make more efficient heat exchangers that captured more of the energy in the first place. But it is a battle of diminishing returns, whereby the expense of the heat exchanger exceeds the value of energy saved.