skip to content
Primary navigation


There are several systems for providing heat to your home, depending on the way heat is distributed throughout the building. Furnaces move heated air through ductwork and into rooms via registers. Boilers heat water and send it to room radiators through pipes. Space heaters provide heat to individual rooms. Wood and biomass, solar, and ground source heat pumps are other forms of home heating.

Furnaces & boilers

Furnaces and boilers are the two most common ways to heat homes; they should be inspected and adjusted annually. ENERGY STAR®, the government-backed program that helps save money and protect our environment with energy-efficient products and practices, says dirt and neglect are the top causes of heating and cooling system inefficiency and failure. It suggests the following measures to improve the efficiency and safety of heating and cooling systems:

  • Change your furnace filter regularly. Check your filter every month, especially during heavy use months. At a minimum, change the filter every three months. A dirty filter will slow down air flow and make the system work harder, wasting energy.
  • Tune up your heating and cooling equipment yearly. Just as a tune-up for your car can improve gas mileage, an annual tune-up of your heating and cooling system can improve efficiency and comfort.
  • Install a programmable or smart thermostat. Both thermostats are excellent for people who are regularly away from home during the week or for long periods of time. 
  • Seal your heating and cooling ducts. Ducts that move air to and from a forced air furnace, central air conditioner, or heat pump are often big energy wasters. Sealing and insulating ducts can improve the efficiency of your heating and cooling system by 20 percent or more.

ENERGY STAR’s Guide to Energy Efficient Heating & Cooling (.pdf)

See pages 31-35 of the Home Energy Guide for information on electric heating systems, wood and biomass systems, solar heating, and ground source heat pumps.

When to replace that old furnace or boiler

Your heating system is vital to the health, safety, and comfort of your home and is one of the most expensive pieces of equipment in homes. Deciding when and how to replace your heating system requires research, so it’s best to begin that process before your system dies.

If your heating system is old, worn out, inefficient, or significantly oversized, the best solution may be to replace it with a new high-efficiency model. Most furnaces have a useful life of 15-20 years, and most boilers will last 20-30 years. But if your home is leaky and poorly insulated, the furnace or boiler will run more frequently than those in tighter homes and they will likely have shorter lives.

Start your research for a new replacement based on:

  • Age. As your furnace or boiler nears the end of its expected life, start planning your replacement strategy, including what to buy and how to pay for it. Utilities often provide rebates for new high-efficiency systems.
  • Expensive repairs. Even if the furnace or boiler has more years of expected life, spending 25% or more of the cost of a new unit on repairs may be a sign that it is time to replace rather than repair.
  • Energy efficiency. A furnace or boiler’s efficiency is measured by annual fuel utilization efficiency (AFUE). Furnaces that deliver 80% AFUE or less and boilers that deliver 70% AFUE or less are costing you real dollars in fuel use. For example, according to the HVAC calculator provided by the Minnesota Center for Energy and Environment, going from an 80% efficient furnace to a 95% efficient one could save about $400 a year in fuel costs.

Before buying a new furnace or boiler, first make every effort to improve the energy efficiency of your home and then have a heating contractor size your system. Energy efficiency improvements will save money on a new furnace or boiler, because you will be able to purchase a smaller unit. A properly sized unit will operate more efficiently. When shopping for high-efficiency furnaces or boilers, always look for the ENERGY STAR® label.Check with utilities or heating contractors if you are considering a new system.

back to top