You have probably had this discussion here many times before but is there a perceived wisdom about which is better?
The subject arises as my grown up daughter has just moved into a house with a conventional boiler and she was going on about what a nuisance it was that the house did not have a combi boiler. My initial thoughts were why complain? - is the combi so good that you'd choose to be with one instead of conventional boiler?
I have never found it very satisfactory whenever I have come across a combi boiler but on this occasion kept quiet as I imagined that things had improved since my last experiences. And anyway who wants a Dad who is out of touch.
Pro combi boilers: Less capital expenditure than conventional No hot water cylinder Usually controls are within the combi casing including pump which saves wiring and /or space and helps to keep cost down. Mains water is used to supply the hot water so that it can be reasonably powerful once set up. Saves heating a (perhaps) unwanted cylinder of hot water which may be a waste of fuel.
Pro conventional boilers No need for a constructed airing cupboard ( the ones I have come across have a very small radiator at the bottom) - build one over the cylinder. Heating of space at the same time as the heating of water to supply hot water. (In my case a considerable advantage as it is at night when the whole family wants a bath or shower in readiness for the next day). (This allows me to go into a heated room to get dry and dressed which is a nicety but also allows the bathroom to be prepared for the next person
- also the house does not go a bit colder.) Filling of a bath from a cylinder can be quicker than a combi can fill the bath. Often cited as the solution to a longer boiler life than the combi and also may be needed for larger houses or condensing boilers. Allows a cylinder full of water to use if needed when the water supply becomes very poor. (Boil for drinking or use for flushing). Also allows for hot water and heating if needed if the mains supply pressure or flow rate drops e g. in some London flats in summer drought mind you there are solutions suggested for low flow rate.
I suppose my primary motivation for asking how people regard them is the fact that we recently rented a house for a month and it had a combi boiler. No doubt the owner saved quite a bit putting that in. The hot water in the bathroom was always OK and the house was warm and cosy but the pipe route and the boiler settings meant that the kitchen was a pain in the neck for hot water - always needing great care in hot water use and despite an econo setting had to be run to get hot.