A disadvantage of condensing boilers compared to customary boilers is:

Condensing boilers indeed tend to have higher upfront costs compared to conventional boilers. This is largely due to their advanced technology and the materials used, which enable them to operate at higher efficiencies by recovering latent heat from the exhaust gases. While they may save money over time through lower operating costs due to their efficiency, the initial investment can be a barrier for some users.

Other considerations such as maintenance or operational noise may affect a user's experience, but the increased purchase price is a significant factor when comparing the initial budget required for installation. The investment in condensing boilers reflects their technology designed for maximizing energy efficiency and can ultimately lead to savings on energy bills, but the higher cost is a notable disadvantage when making a decision between boiler types.