Price guide

How much does an unvented hot water cylinder cost?

Short answer

One Wiltshire firm fits a like-for-like unvented cylinder from £1,640 plus VAT, and gives £1,500 to £3,000 for most replacements. A Gloucester firm prices a system boiler with a new unvented cylinder at £3,800 to £5,500 plus VAT. A yearly service starts at about £75 plus VAT. Get at least three written quotes.

Updated 15 October 2026 · 2 min read · 5 sources

What firms near the Cotswolds charge

Published prices for a like-for-like unvented cylinder start at about £1,640 plus VAT. We found few firms in the Cotswolds that publish cylinder prices. The firms below are in Gloucester and Wiltshire.

A change from a tank-fed system to an unvented cylinder costs more. It can also need a new boiler, new pipes and the removal of the loft tanks.

Unvented cylinder prices published by firms near the Cotswolds
Firm (base)	Job	Published price
Rosebourne Plumbing (Andover and Marlborough)	Like-for-like unvented cylinder, supplied and fitted	From £1,640 plus VAT
Rosebourne Plumbing (Andover and Marlborough)	Unvented cylinder replacement, typical range	£1,500 to £3,000 plus VAT
Rosebourne Plumbing (Andover and Marlborough)	Worked example: 170 litre cylinder in Marlborough	£2,170 plus VAT
Priority One Plumbing (Gloucester)	System boiler with a new unvented cylinder	£3,800 to £5,500 plus VAT
Philip Cheeseman & Sons (Melksham)	Unvented cylinder service	£75 plus VAT
Philip Cheeseman & Sons (Melksham)	Unvented cylinder and boiler service together	£145 plus VAT

Prices that each firm publishes on its own website, checked on 15 October 2026. Rosebourne’s guide is dated 21 March 2026. The Cheeseman price page was last changed in January 2025, so its prices may be out of date. These are not quotes for your home. Sources: Rosebourne Plumbing (Andover and Marlborough): hot water cylinder replacement cost, 2026 guide (21 March 2026), Priority One Plumbing (Gloucester): boiler installation, Philip Cheeseman & Sons Plumbing & Heating (Melksham): prices.

National prices

A national cost site gives a lower figure for a simple swap. This is a national figure, not a Cotswold quote.

National price for an unvented cylinder
Source	Job	National price
HaMuch cost guide	Replace an unvented cylinder, supply and fit	About £1,050

National figure from the HaMuch unvented cylinder cost page (updated 9 April 2025), checked on 15 October 2026. The page says its prices may not include VAT. It is not a local price. Sources: HaMuch: cost to fit an unvented cylinder (updated 9 April 2025).

The rules that affect the price

Approved Document G says an unvented system is notifiable building work. An installer on a competent person scheme can self-certify it. Otherwise you must notify building control before work starts, which can add a fee.

The installer should have the right skills, shown by a competent person scheme or a current unvented skills card. Ask to see proof.

An unvented cylinder needs a safe discharge pipe. A long or awkward route to the outside adds cost.

How to compare cylinder quotes

Prices vary; get at least three written quotes. Ask each firm the same questions.

Ask for the cylinder make, size and warranty length.
Ask if the price includes the valves, discharge pipe and removal of the old cylinder and tanks.
Ask if the firm will test the mains pressure and flow first.
Ask who notifies building control, and what certificate you will get.
Ask if the price includes VAT, and what a yearly service costs.

Questions

Does an unvented cylinder need a yearly service?

Most makers ask for one to keep the warranty. Check the maker’s instructions. One Melksham firm charges £75 plus VAT.

Is an unvented cylinder worth it?

It gives mains pressure at every tap, which suits homes with more than one bathroom. It needs good mains pressure and flow. Ask a plumber to test yours.

Do I need building control?

Yes, unless the installer is on a competent person scheme for unvented hot water. Then they self-certify the work.