Combi Boiler Installation Cost 2026: What Sussex Homeowners Really Pay

36+ years. 1,000+ installations. Gas Safe registered.

If you are searching for the real combi boiler installation cost in 2026, you probably want a straight answer.

For a typical Sussex or Surrey home, a new combi boiler installation usually costs between £1,800 and £3,500, including supply and fitting.

A straightforward like-for-like replacement often falls between £2,000 and £3,200. More involved work, such as relocating the boiler or converting from another type of heating system, can cost more.

At Boilers On-Demand, selected standard installations start from £1,699 fitted. Some boilers also come with manufacturer guarantees of up to 12 years, depending on the model, installer requirements and registration terms.

These are realistic guide prices. Not a headline figure with essential work removed.

How Much Does a Combi Boiler Installation Cost in 2026?

Here is the honest price breakdown for a domestic combi boiler replacement:

The final boiler installation cost depends on the property, existing pipework, flue position, boiler output and what is included in the quote.

A price of £1,699 may suit a straightforward installation. It will not apply to every home. A proper survey tells you where your installation sits within the range.

What Is Included in a Fair Boiler Installation Cost?

A clear quote should show exactly what you are paying for.

For a standard combi boiler replacement, the price should normally cover:

• Supply of the new boiler.
• Removal and responsible disposal of the old boiler.
• Standard installation materials.
• Flue and terminal installation.
• Connecting the boiler to the heating and hot water systems.
• Gas safety checks.
• Testing and commissioning.
• Benchmark documentation.
• Manufacturer guarantee registration.
• A clear handover explaining the controls.

At Boilers On-Demand, old boiler removal is included as standard.

Be careful with unusually cheap quotes. The advertised figure may exclude items such as:

• Boiler removal.
• New controls.
• Magnetic filters.
• Flue alterations.
• System cleaning.
• Commissioning.
• VAT.
• Guarantee registration.

The cheapest quote is not always the cheapest job. If important work has been left out, the price usually appears later.

Where Does the Money Go?

A typical combi boiler installation cost is made up of several parts.

1. The Boiler

The boiler itself is usually the largest single cost. Prices vary by brand, output and guarantee length.

We install established manufacturers including:

• Vaillant
• Glow-worm
• Baxi

As a broad guide, Glow-worm and Baxi often provide lower-cost options, while Vaillant models may sit towards the premium end.

The right boiler is not simply the biggest or most expensive one. It needs to suit your home, radiators, hot water demand and incoming mains pressure.

2. Labour

A straightforward same-location combi replacement is often completed within one working day.

Labour costs increase when the installer needs to:

• Move the boiler.
• Upgrade gas or water pipework.
• Alter the flue.
• Remove tanks or cylinders.
• Replace damaged valves.
• Fit new controls.
• Clean or rebalance the heating system.

Good installation takes time. The boiler needs to be safely connected, tested and commissioned properly before the engineer leaves.

3. Filters, Controls and System Protection

A magnetic filter can help reduce sludge and debris circulating through the system. New heating controls can also improve comfort and efficiency.

These items may add to your initial boiler replacement cost, but they can protect the new boiler and may be required for certain extended manufacturer guarantees.

A proper installer should explain why an extra is being recommended. You should not be presented with a long list of unexplained additions.

What Makes a Combi Boiler Installation More Expensive?

Keeping the Boiler in the Same Location

A like-for-like replacement is usually the most affordable option. The existing flue, pipework and electrical connections may be reusable, subject to inspection.

This is why many standard installations cost around £1,800–£3,200.

Moving the Boiler

Relocating a boiler to a loft, airing cupboard, garage or different wall can add £800–£1,200 or more.

The additional cost may include:

• Longer heating and water pipework.
• A new flue route.
• Condensate pipework.
• Electrical changes.
• Additional supports or boxing-in.
• Extra testing and commissioning.

Relocation can be worthwhile. It just should not be priced as a basic replacement.

The Condition of Your Existing Heating System

Older systems can contain sludge, corrosion or restricted pipework. If this is ignored, it may affect the performance of your new boiler.

Your installer may recommend:

• A system clean.
• A power flush.
• A magnetic filter.
• Replacement valves.
• New radiators.
• Upgraded heating controls.

These are not automatically unnecessary extras. They can help the new boiler run reliably and protect your investment.

The Size of Your Home and Your Hot Water Demand

A small flat with one bathroom has different requirements from a four-bedroom home with several occupants.

Boiler sizing depends on:

• The number of radiators.
• The size and insulation of the property.
• Number of bathrooms.
• Mains water pressure.
• How often hot water is used at the same time.
• The existing heating layout.

An oversized boiler can cost more than necessary. An undersized boiler may struggle to keep up.

We assess the property before recommending a model. That is the old-fashioned way: look at the job first, then price it properly.

Combi Boiler Cost by Brand

The brand affects the unit price and available guarantee. It is not the only factor.

Vaillant

Vaillant is often selected by homeowners looking for a premium boiler with strong efficiency and longer guarantee options.

Selected Vaillant models may offer guarantees of up to 12 years when installed by an approved installer with the required protection equipment and registration.

Baxi

Baxi offers several popular combi ranges across different price points. Depending on the model and installation conditions, selected boilers may come with guarantees of up to 12 years.

Glow-worm

Glow-worm can be a practical option for homeowners looking to control the upfront boiler installation cost. Selected models may offer guarantees of up to 12 years when the relevant installer and registration requirements are met.

Always ask for the exact model, guarantee length and terms. "Up to 12 years" does not mean every boiler automatically receives 12 years of cover.

What Does "Up to 12 Years' Guarantee" Really Mean?

At Boilers On-Demand, selected installations can include manufacturer guarantees of up to 12 years.

The exact guarantee depends on:

• The boiler model.
• The manufacturer's current terms.
• Whether an approved installer scheme is required.
• Whether a system filter or protection kit must be fitted.
• Registration within the manufacturer's timescale.
• Annual servicing requirements.

For example, manufacturer terms commonly require the boiler to be:

• Installed by a suitably qualified Gas Safe registered engineer.
• Registered promptly after installation.
• Serviced every year.
• Maintained according to the manufacturer's instructions.

Do not rely on a verbal promise. Ask for the guarantee details in writing and keep your installation paperwork and service records.

Why Choose a Local Sussex Boiler Installer?

We have served Sussex and Surrey since 1988.

We are not a national call centre. You speak to a local team that understands the homes, housing types and heating problems found across the area.

We work with homeowners in places including Brighton, Eastbourne, Hastings, Lewes, Uckfield, Hailsham, Seaford, Horsham, Billingshurst, Steyning, Petworth, Storrington, and across Surrey and the surrounding villages.

Our credentials are straightforward:

• 36+ years serving local homeowners.
• 1,000+ boilers installed.
• Gas Safe registered, registration number 575142.
• Vaillant, Glow-worm and Baxi installation options.
• Most straightforward installations completed in one day.
• Old boiler removal included as standard.
• Flexible finance options available, subject to status and credit checks.
• Manufacturer guarantees of up to 12 years on selected installations.

Gas Safe Registration Is Not Optional

Gas boiler installation is safety-critical work.

Always check that the company and engineer are qualified for domestic gas work. You can verify registration through the official Gas Safe Register.

Boilers On-Demand is Gas Safe registered under No. 575142.

A low price is not worth risking your family's safety, your property or your manufacturer guarantee.

Our Price Promise: Clear Quotes Before Work Starts

We will assess your current boiler, pipework, controls and flue before giving you a final price.

You will receive a clear quote showing:

• The boiler model.
• Installation work.
• Included materials.
• Any recommended extras.
• Guarantee information.
• What happens to the old boiler.
• The expected installation timescale.

No surprise charges. No pressure to choose the most expensive option.

If finance would help, flexible options may be available so cost does not stand between you and a properly working heating system.

Get an Honest Combi Boiler Installation Cost for Your Home

Online guides can give you a useful starting point. They cannot see your boiler, flue, pipework or radiators.

For an accurate price, request a free boiler survey and quote or use our online quote service.

Call 01903 802395. We will explain your options clearly and tell you what the work is likely to cost.

No hard sell. Just a straight conversation.

Frequently Asked Questions

How much does a combi boiler installation cost in 2026?

A typical combi boiler installation costs around £1,800–£3,500, including supply and fitting. A straightforward replacement in the same location is often £2,000–£3,200. Selected Boilers On-Demand installations start from £1,699.

What is the average boiler replacement cost UK homeowners should expect?

For a standard combi-to-combi replacement, many homeowners should budget around £2,000–£3,200. Relocation, major pipework changes, or conversion work can increase the total to £3,500–£5,000 or more.

How long does a combi boiler installation take?

Most like-for-like combi boiler replacements are completed in a single day. More complex installations may take longer. Your installer should confirm the expected timescale before work begins.

Do you remove the old boiler?

Yes. Boilers On-Demand removes and responsibly disposes of the old boiler as standard during a new installation.

Can I get a guarantee of up to 12 years?

Selected boilers and installation packages may include manufacturer guarantees of up to 12 years. The exact term depends on the model and conditions, including correct registration and annual servicing.

Is a combi boiler suitable for every home?

No. Combi boilers suit many smaller and mid-sized homes, particularly those with moderate hot water demand. A survey is the best way to establish whether one is suitable for your property.