What Is a Boiler?
A boiler heats water and uses that heat to warm your home. Instead of blowing air, it moves hot water or steam.
How a Boiler Works
- Fuel heats water inside the boiler
- A pump moves hot water (or steam) through pipes
- Heat is released through radiators or floors
- Cooler water returns to the boiler to be reheated
Technical note:
Hot water systems are called hydronic systems.
Types of Distribution for a Boiler Heating System
- Radiators – common in older homes
- Baseboard heaters – long units along walls
- Radiant floor heating – pipes under the floor
Why it matters:
Water holds heat better than air, so boilers provide steady, even warmth.
Types of Fuel
- Natural gas
- Oil
- Propane
- Electricity
Efficiency Ratings
Boilers also use AFUE ratings:
- Older systems: 60–70%
- Modern systems: 80–95%
Boiler vs. Heat Pump Comparison
| Feature | Fossil Fuel Boiler | Heat Pump |
|---|---|---|
| Heat Medium | Water/steam | Air or Water (geothermal) |
| Efficiency | AFUE 80–95% | COP 2–5 |
| Comfort | Very steady | Quick response |
| Cooling | No | Yes |
| Distribution Loss | Low (pipes) | Moderate (ducts) |
| Emissions | High | No onsite emissions |
Key Takeaway
Boilers are great for comfort and even heat. But like furnaces, they rely on fossil fuels and do not provide cooling.
