
System boiler replacement
Plan your replacement around the complete hot-water system. Get a Free Estimate
System boilers are often used in homes where stored hot water is useful, particularly where there are multiple bathrooms or periods of higher demand. When replacing one, it is important to look beyond the boiler itself because the hot-water cylinder, controls and wider heating arrangement all affect how the system performs.
If the existing arrangement is working well, a replacement system boiler may be relatively straightforward. If the cylinder is ageing, the controls are dated or the household has changed, the replacement also provides an opportunity to review those parts of the setup. We help homeowners understand which changes are necessary, which may be useful and which can reasonably remain as they are.

A system boiler works together with stored hot water, controls and the heating circuit. That makes it important to assess these connected parts rather than treating the replacement as a single-appliance job.
The condition, size and arrangement of the existing cylinder should be considered because it plays a central role in how stored hot water is supplied.
The new system boiler should be selected according to the property's heating requirements and the way the stored hot-water system is set up.
Larger homes may use separate heating or hot-water schedules. The existing control arrangement should be reviewed during replacement planning.
Keeping the boiler in the same suitable location can make replacement simpler, while relocation may involve additional pipe, flue and condensate work.
Radiators, valves and heating-system water should be taken into account so the replacement boiler is being connected to a system in reasonable condition.
| Service | Estimated Cost | Average |
|---|---|---|
| Like-for-like system boiler replacement | About £2,200-£3,800 | Around £3,000 |
| System boiler with controls or minor alterations | About £2,800-£4,800 | Around £3,800 |
| Replacement involving cylinder or wider system changes | About £4,000-£7,000+ | Around £5,500 |
These broad estimates are for planning only. The boiler, cylinder, controls, pipework and amount of alteration required all influence the eventual quotation.

We consider the cylinder and controls alongside the replacement boiler.
The discussion starts with how heating and hot water are actually used in the home.
We distinguish between work required for the replacement and additional improvements you may wish to consider.
We work with a range of larger homes and established heating systems across the Milton Keynes area.
Need to replace a system boiler? Tell us about the boiler, cylinder and number of bathrooms so we can start with the right questions.
Free — no obligations

We review the boiler, cylinder, controls and how the household currently uses hot water.
The condition and suitability of connected parts of the system are considered.
We explain what can remain, what needs changing and any optional improvements.
The old boiler is removed and the new system boiler fitted with the agreed changes.
The controls, heating and hot-water operation are checked and explained.