How a combi boiler works
A combi boiler heats water directly when you open a hot tap, while also serving the central-heating circuit. Because hot water is not stored in a separate cylinder, a combi can free up cupboard space and remove the need for a hot-water storage tank. This arrangement is often simpler where a household has modest simultaneous hot-water demand and the incoming mains supply is suitable.
The trade-off is that a combi heats water as it is used. If several showers or taps are likely to run at once, the delivery of hot water may be shared between them. Homes with more than one bathroom or a busy household should think about real usage patterns, not just the number of bedrooms. Tell us which outlets matter most and whether anyone regularly uses them together.
Choosing a suitable output
Combi models are available in different outputs. The central-heating load and the hot-water flow requirement are related but not identical: a home can need a modest heating output yet still benefit from a combi with more hot-water capacity. An installer will consider the home, radiators, water demand and boiler model rather than using floor area alone.
The calculator uses your answers to suggest suitable boiler sizes and prices from Ideal, Worcester Bosch and Vaillant. Ideal is shown first as the recommended option in the combi results; the other matching models are displayed for comparison. The calculator is a guide and should not be used to specify equipment without checking the property and existing system.
Replacing a combi or converting from another boiler
If you already have a combi in a suitable position, a like-for-like replacement may be relatively direct, although the flue, pipework, controls and system condition still need to be inspected. Replacing a standard, system or back boiler with a combi is a conversion. It can involve removing redundant tanks or cylinders, adapting pipework, choosing a new boiler position and dealing with the old system safely.
A back boiler conversion is a more involved job and the online journey treats it separately. The old appliance arrangement, fireplace and pipe routes need to be understood before a final quote is confirmed. For a system or heat-only boiler, compare the possibility of retaining stored hot water against the space savings of a combi. Our guide to system and heat-only boilers explains those options.
Flue, controls and installation details
The flue carries combustion products safely outside and must be installed in a suitable position. The calculator asks about the route and certain clearances because a roof flue or another non-standard arrangement changes the equipment and work required. Do not move, cover or modify an existing flue yourself. The installer checks the proposed route and the relevant requirements before confirming the job.
Controls, water quality, pipework and drainage also matter. An installer can explain whether the existing controls can be reused or whether a different control is needed for the new boiler. They will assess whether the system needs remedial work before the replacement can be commissioned. The quotation should describe the equipment and work included, so ask about anything that is unclear before booking.
Price, warranty and next steps
1st Climate's homepage shows new boilers installed from £2,030. A combi's guide price varies by model, output and installation choices such as flue route. A conversion will not cost the same as a basic swap because the work can be different. Use the calculator to see the current guide price for the answers you provide, then have the details checked before accepting a fixed quote.
Selected boiler installations may be eligible for warranties of up to 12 years, subject to product and manufacturer terms. Ask how the warranty is registered and what servicing requirements apply. Next-day installation and monthly payment options may be available; confirm availability, terms and eligibility directly. To begin, choose the combi option in the online quote journey. Your contact details are requested after you have worked through the questions.
Common questions
Are combi boilers suitable for every home?
No. They suit many homes, but household hot-water demand, the mains supply, system layout and available installation position all need to be considered.
Can a standard boiler be changed to a combi?
Yes, a conversion may be possible, but it involves more checks and work than a like-for-like swap. The old cylinder, tanks, pipe routes and new boiler position need assessing.
What size combi boiler do I need?
The right output depends on both heating demand and hot-water use. The calculator suggests matching models from your answers, and an installer checks the home before confirming a model.
Which combi boiler brands does 1st Climate offer?
Ideal, Worcester Bosch and Vaillant combi options are available through the calculator, with Ideal shown first as the recommended option.