Combi boiler
No separate cylinder, subject to mains flow and simultaneous demand.
HOME HEATING
Compare boilers and heating-system options
The right boiler depends on hot-water demand, existing cylinders and pipework, not simply the largest quoted output or longest headline warranty.
Decision routes
Start with the outcome, not the advert
System boiler
Works with a cylinder for homes with greater hot-water demand.
Boiler vs heat pump
Compare fabric, emitters, fuel and long-term plans before replacement.
The CoolCompare check
Four things to compare before committing
Compare combi, system and regular boilers by property fit, hot-water demand, controls, warranty and installed scope.
Boiler typeMatch combi, system or regular architecture to the property.
Hot-water demandBathrooms and simultaneous use affect the sensible route.
ControlsWeather compensation and zoning can matter as much as the appliance.
Quote scopeFlue, filter, controls, flush, condensate and warranty should be visible.
Side-by-side
Compare the main routes
A quick orientation before you request prices or commit to a contract.
| Decision | Combi | System | Regular |
|---|---|---|---|
| Hot water | On demand | Stored cylinder | Stored cylinder |
| Loft tanks | Usually none | Usually none | Often retained |
| Good fit | Lower simultaneous demand | Higher hot-water demand | Existing traditional systems |
| Check first | Mains flow and pressure | Cylinder recovery and space | Tanks, pump and controls |
Before you buy
Your quote and contract checklist
Save this list and use the same questions with every provider. Comparable inputs produce a more useful comparison.
- 01
Exact model and outputSeparate space-heating output from domestic hot-water performance.
- 02
System preparationState flushing, filter, inhibitor and existing-system condition.
- 03
Flue and condensateConfirm routes, access, plume management and making good.
- 04
Controls and warrantyList controls, registration, servicing conditions and labour cover.
Start here
Essential boilers guides
Three practical reads that frame the decision without sales pressure.
TYPES01
Combi vs system boiler
Choose around hot-water demand and the existing home.
Read the key answers ↓QUOTES02
How to compare boiler quotes
A line-by-line scope checklist for a fair comparison.
Read the key answers ↓PLANNING03
Boiler or heat pump?
Frame replacement as a whole-home strategy decision.
Read the key answers ↓Plain-English answers
Frequently asked questions
General UK guidance. Product, property, tariff and policy details still need individual verification.
Is a bigger boiler better?+
No. Oversizing can reduce controllability, while combi hot-water output and space-heating demand are different requirements.
When does a system boiler make sense?+
Stored hot water can suit homes with higher simultaneous demand, provided the cylinder and recovery design are appropriate.
What should a boiler quote include?+
Exact equipment, controls, flue, condensate, electrical work, system cleaning, filter, commissioning, warranty and exclusions.
Should I replace radiators with a boiler?+
Only where condition, balance or lower-temperature planning justifies it. Ask for the reason room by room.
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