Central heating system not used/turned off for two years - how much of a problem could this be?

[nonegotiation]

Currently in the process of buying a property and the survey has come back stating the gas and hot water have been turned off for ‘several years’ and the only source of hot water currently is the electric shower. They had a log burner fitted in 2023 so I assume this is when they stopped using the central heating.

We obviously need to weigh up our options and will know more once a gas safety cert has been completed and then a gas engineer been out to look at the system but does anyone have experience of this? And what state was the system in when it was restarted and serviced etc? Obviously worst case scenario is a whole new system is needed but hoping to hear someone else has experience of this and it wasn’t awful just a few repairs were needed?! Or am I being very optimistic here!

We stopped using our ancient central heating system for about a year when our boiler was condemned. When we did finally get it back up and running the pump had seized, but a few swift bashes with a spanner freed it again and all works ok now.

There are not many moving parts in a central heating system. It depends how old it is. It needs to be full of water. If you can get your hands on an experienced and reputable local heating engineer or plumber, s/he should be able to tell if it's in a bad way. An unqualified person will not be able to work on the gas boiler, but can do the pipes, valves and water. If it was me I would want to give it at least a chemical clean and flush (this is easier and cheaper than a powerflush, which you might or might not find is necessary after assessment) and refill with clean water and inhibitor.

You may find some of the old valves are seized. They can last around 10 to 50 years, and are replaceable parts

P.s.

It's quite possible that they stopped using the boiler because it was old and beyond economic repair

They are probably hoping that "in an unused state for 2 years" is less detrimental to their house value than "broken beyond repair".

Just budget for a complete system in your offer if you make one. I agree it may be that they stopped using it because it was in need of replacement.
Another option would be to make an offer with the provision that the system is serviced and returned to full working in order. If they refuse I would think I need to budget for it all being knackered.

Ok thank you all that was the bit of reassurance I needed! But yes like you have all pointed I do suspect it could well be buggered…

The boiler should be serviced before the sale - that's good practice. If it's serviced the gas engineer will be able to see if it's actually working or not. It needs to be working to be serviced properly.

It might be worth paying for a gas safe engineer to go and have a look and do an assessment of the gas/water in the property.

I work for a gas engineer. This is something we do quite regularly.

This is exactly what we have just suggested, we are happy to get it serviced as I want it to be by someone I trust so we have said if they pay for a gas safety cert and get it back on we will pay for the service and get an idea of any future costs.