ProtectHOMEOWNER GUIDE
Combi or system boiler: compare the full installation
The correct system depends on your property and demand.
Understand the broad difference
A combi normally provides hot water on demand, while a system boiler works with a hot-water cylinder. Suitability depends on the property, incoming supply and hot-water requirements; a competent heating professional should assess these.
Compare the changes required
A switch can involve cylinder installation or removal, pipework, controls, electrical work and making good. Ask whether each quote covers the same work.
Request the specification
Get the proposed make, model, output and controls in writing. Ask why they suit your home and which commissioning and warranty documents will be supplied. A room count alone cannot establish the correct design.
Reviewed 4 October 2026 · ProtectMyQuote editorial guidance
Put the questions into practice
Our report organises questions for your type of job. Our agreement helps you record what is accepted. See the sample documents before deciding.
Make the next step a clearer one.
Ask the right questions. Put the answers in writing.