Most of us don’t know much about the furnace or boiler in our basements other than that they ensure our homes are delightful when the weather outside is frightful. We use the terms “furnace” or “boiler” interchangeably and hope for the best.
But not fully understanding these two home heating system workhorses is a lost opportunity. Understanding the ins and outs of a furnace vs. boiler can help you make better decisions about which one is best for your home energy needs, which in turn can help you better budget your energy costs. There is a difference between boiler vs. furnace energy efficiency, for instance.
Let’s start with the basics of how a furnace vs. boiler works.
Boilers are typically more expensive than furnaces. Home improvement site KompareIt says boilers, which are more complex to install than furnaces, typically cost $2,500-$4,000 for a mid-range model, while high-efficiency boilers cost between $5,000-$10,000, including installation. Steam, gas and hot water boilers cost about the same, but steam boilers operate less efficiently so that’s something to keep in mind as you consider which boiler is best for your household energy needs. Removal of your old boiler can range from $500-$1,000, depending on the size and difficulty of the removal from your basement.
Here are some basic boiler pros and cons:
When considering whether to go with a furnace vs. boiler, cost can matter. KompareIt says the average furnace costs between $2,000-$3,500, including installation. High-efficiency models can run $5,000 and up, including installation. Removal of an old furnace can cost as much as $1,000, depending on size and difficulty.
Here are some basic furnace pros and cons:
The first thing to note when thinking about your heating energy efficiency is the age of your furnace or boiler. Energy.gov says that older furnace or boiler systems generally were only energy efficient in the 56-70% range. Today’s systems can be as high as 98.5%. That means that practically all the fuel you buy goes directly toward heating your home. Having a more energy-efficient furnace or boiler can mean cutting your fuel bills and pollution output in half. Upgrading your furnace or boiler from 56% efficiency to the 90% range, Energy.gov says, could save 1.5 tons of carbon dioxide emissions annually if you heat with gas. That number goes up to 2.5 tons if you heat with oil.
Some easy ways to improve energy efficiency include considering the various types of furnaces or boilers. Energy.gov recommends switching a gas furnace that has a pilot light, for instance, to one with electronic ignitions.
Energy efficiency in boilers and furnaces is measured the same way — by annual fuel utilization efficiency (AFUE). A unit that has an AFUE of, say 70, converts 70% of its fuel to heat. The other 30% is lost. The federal government dictates that gas- and oil-powered furnaces can’t have an AFUE rating of lower than 78%. High-efficiency furnace models must have AFUE ratings of 85% or higher.
AFUE ratings for boilers depend on the type of boiler and its heating source. KompareIt says that steam boilers running on oil have a minimum AFUE of 82%. A steam boiler running on gas, meanwhile, would have a minimum of 80%. Hot water boilers have a minimum of 82% for gas models and 84% for models that run on oil.
Energy.gov says boiler vs. furnace energy efficiency can also be compared by noting certain equipment features. In addition to looking at AFUE percentages, Energy.gov suggests taking note of whether or not the heating system has a pilot light. Having a continuous pilot light, for instance, is less energy efficient that either having no pilot light or having a system that condenses flue gases in a second heat exchanger that provides extra efficiency. The most energy efficient heating systems also have sealed combustion.
This chart from Energy.gov can help you analyze boiler vs. furnace energy efficiency at a glance:
It doesn’t matter whether you have a furnace or a boiler— if you don’t take care of it, it won’t operate at its optimum. And that means you could be losing money as you heat your home less efficiently. Here are some recommended maintenance tips from Energy.gov.
For all systems:
For forced air systems:
For hot water systems:
For steam systems:
Ultimately, the energy efficiency of your home can save — or cost — you money. Although you might not think too much about your furnace or boiler when everything seems to be working fine, it’s important to understand how they work so that you know you’re doing the best you can to keep your home running efficiently. Performing the recommended routine maintenance on your furnace or boiler can save you a lot of money (and headaches), so check out your system soon!
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