Gas-Fired Boilers and Furnaces

Gas boilers and furnaces can be fueled by either natural gas or propane, with simple modifications to account for the different characteristics of these fuels. Natural gas is widely available throughout the United States but requires a local distribution system. Propane is delivered by truck and stored in a large tank, typically around 500 gallons, but is usually a more expensive fuel.

Retrofit Options to Consider

Before considering any upgrades to your gas-fired furnace or boiler, think about the potential benefits of simply replacing the furnace.

Vent Dampers

A common retrofit is adding a vent (or flue) damper to a boiler. A vent damper prevents heat losses by closing off the boiler's vent when it’s not firing. Steam boilers benefit from vent dampers more than hot water boilers, and larger boilers benefit more than smaller ones. However, vent dampers might not be cost-effective with newer, properly sized models.

Next Step: Consult with a professional to see if a vent damper is right for your system.
 

Intermittent Ignition Devices

Older furnaces and boilers with continuous pilot lights should be upgraded with intermittent ignition devices (IIDs). These devices automatically shut off the pilot light when the system is not in use, saving between 3% and 5% in fuel (source: Residential Energy, 5th Edition, by John Krigger). This update should only be installed by an HVAC professional.

Homeowners with equipment equipped with continuous pilot lights should also discuss the cost-effectiveness of upgrading their systems to sealed combustion or heat pump equipment.

Next Step: Contact a qualified technician to install an intermittent ignition device.
 

Modulating Aquastats (For Hot Water Boilers Only)

An aquastat controls the temperature of the hot water in a boiler, typically keeping it between 160-180°F. During mild weather, boiler water temperatures may be turned down to help save energy. A modulating aquastat, also known as an outdoor reset, senses outdoor temperatures and adjusts the hot water temperature accordingly, usually to 120-140°F. This helps to reduce fueld consumption by 5-10%. (Source: Smarter House – Energy Saving Tips)   A cheaper alternative is to manually adjust the aquastat yourself, turning it down to around 120°F during the milder heating season. Consult your owner's manual or a service technician to locate the aquastat.

Next Step: Talk to a qualified contractor about installing a modulating aquastat to optimize your boiler’s efficiency.

Time Delay Relay (For Hot Water Boilers Only)

A time delay relay helps your system make the most of the heat already in the system without running the boiler. When the thermostat clicks on, the relay causes the boiler to circulate hot water through the system without immediately turning on the boiler, reducing fuel costs by up to 10%. (Source: Smarter House – Maintenance) After a set time, the boiler will fire up. A time delay relay costs about $100.

Next Step: Install a time delay relay to maximize your boiler’s efficiency.

Take Action

  • Check out different models of high-efficiency gas-fired boilers and furnaces to find the best fit for your home.

  • Consult with a professional to evaluate your current system and discuss the best retrofits or replacements for improved efficiency.

  • Explore our Energy Saver Guide to find more tips on how to save energy and reduce your heating costs.

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