A boiler is better if you want lower operating costs. And a combi boiler can provide your hot water too. Boilers are better if you have allergies, which can be made worse by a forced air gas furnace carrying dust and other allergens around your home.
A furnace is better when you want lower upfront costs – the cost to have a furnace installed is almost always lower than the price of a boiler installed.
In terms of home insurance, having a boiler system might lower your insurance rate slightly. They are generally safer to use – causing fewer house fires. However, because they are water systems, they can leak and cause water damage.
Boiler vs Furnace Efficiency
You have many fuel options for both heating system types.
This chart can be used to compare boilers vs furnaces in terms of efficiency. The range for gas furnaces is for high-efficiency furnaces. You can also buy 80% efficient gas furnaces.
Boiler Vs Furnace Efficiency
| Fuel Type | Boiler Efficiency | Furnace Efficiency |
| Natural Gas | 90% – 97% | 91.2% – 99% |
| Propane | 90% – 97% | 91.2% – 99% |
| Oil | 87% – 91% | 85% – 96.7% |
| Electric | 99% – 100% | 99% – 100% |
| Wood | 40% – 90% | 40% – 90% |
The boiler vs furnace energy efficiency data in the charts was obtained through lengthy research on the US DOE Energy Star pages for boilers and for furnaces.
Efficiency Doesn’t Always Equal Cost to Operate!
For example, electric furnaces and boilers are very efficient in that they convert electricity to heat very well – but electricity costs are higher than other fuel costs in most states, so an electric HVAC system is the most costly to operate.
What about the other types?
- Natural gas (NG): In most places, gas is the cheapest heating fuel type.
- Propane (LP): Propane systems can be just as efficient as natural gas, but propane costs more in most regions of the country.
- Oil / Home heating oil: Oil systems are not recommended unless you live in an area like the Northeastern US that has limited access to natural gas and propane. Heating oil cost is higher than both gas types.
- Wood: New wood furnaces and boilers are fairly efficient. Older models are not. If you are heating with an old wood system, you might want to replace it with a new one that can boost energy efficiency quite a bit. In terms of operating cost, it varies. Wood cost is low where wood is abundant. In fact, in many heavily wooded states of the north, free wood can be obtained on state or federal land. Note: If the wood furnace or boiler is installed in your home rather than outdoors, expect higher home insurance rates.
Boiler vs Furnace Monthly Cost
What costs less to run, a furnace or a boiler?
A boiler.
In almost all cases, a boiler costs less to operate than a furnace. Your boiler vs furnace monthly cost will depend on three factors:
1). How much heat you need is an obvious factor. In Minnesota, monthly heating cost is much higher than in Mississippi, for example, for any fuel type other than free wood.
2). How efficient the boiler and furnace are that you are comparing.
3). Your local cost of the fuel type you need. Natural gas and propane cost significantly less in gas-producing states like Texas and Oklahoma than in non-producing states.
Wood is cheaper in areas where it is abundant. Electricity prices vary widely across the country, currently from about 10 cents per kWh to more than 25 cents per kWh.
Determining monthly costs: To determine operating costs, you have to know the cost of the fuels you’re comparing and how much of the fuel you’re likely to use.
Your past energy bills tell you how much energy you’ve used in the past. You can use the information to determine likely fewer use and cost of upgrading your furnace or boiler to a more efficient model.
Upfront vs operating costs: Boilers cost less to operate than furnaces. But they cost more upfront. How long does it take to pay back the higher cost? In cold climates, the higher cost of the boiler is recouped in an average of 4-7 years. In warmer climates, it’s often 10 to 20 years.
Do Boilers Last Longer Than Furnaces?
Yes. Boilers last longer than furnaces across all fuel types.
- Furnaces last 15 to 25 years
- Boilers last 20 to 30 years – and sometimes up to 40 years
The durability of both furnaces and boilers depends on initial quality, proper or faulty installation, how heavily they are used and how well they are maintained.
Boilers generally require less maintenance. For this reason, a poorly maintained furnace will have mechanical issues and need to be replaced before a boiler that isn’t regularly maintained.
Standard vs High Efficiency? High-efficiency furnaces and boilers are also called condensing furnaces and boilers. And they don’t last as long as standard-efficiency units. Why?
This is because their exhaust condenses – cools enough that the moisture in it changes from vapor to water droplets. And the water contains highly corrosive carbonic acid. As a result, they are made with stainless steel exhaust. However, in time, the corrosive water gets into the “works” and can cause rust and ultimately failure.
