Between Gas and Electric Heaters, Which is Most Efficient?

Whether you’re remodeling or starting anew, you’re likely weighing alternative heater solutions. How do you determine which is the best (aka the most efficient)? Here’s a straightforward comparison between two considerably different alternatives: Central AC with a gas furnace (arguably the most common of all HVAC systems) and a ductless AC multi-zone system with electric heat.

Central AC with Gas Furnace for Heat

This one is about as straight forward as they come - and just about everyone in the home remodeling and/or building industry is familiar with it. A gas-fired heat exchanger generates the warmth you need in the winter and a DX cooling coil (coupled to an exterior condensing unit) provides the cooling you want in the summer. Such furnaces are typically located in the basement and are controlled by a single thermostat, so that all rooms in the house are warmed and cooled simultaneously, or they may have multiple zones. The warm or cold air is circulated throughout the house by using a series of ducts and vents.

Ductless AC Multi-Zone System with Electric Heat

While still growing in popularity in the US, ductless systems are widely used in other parts of the world. These systems, also referred to as “mini splits”, are comprised of an indoor heat pump incorporating a fan and heating/cooling coil, can be installed independently at multiple points throughout the house. (Normally, you’d have one outdoor condenser installed for every three indoor units). The condensing unit is typically smaller than ones utilized in the more traditional central AC systems described above, and is often shaped like a rectangular box having dimensions approximating 30”x35”x12”.

One of the biggest advantages of ductless multi-zone systems is that each of the units is controlled by its own respective thermostat, allowing different spaces in the house to accommodate different temperatures, or more uniform cooling and heating throughout, depending on what your specific needs are. Also, because there are no ducts, this solution not only offers space savings and less complex installations, but also offers increased energy efficiency because there is no heat loss during the transfer process that would occur in a a standard duct and vent system. Such ductless systems are well suited for renovations in existing buildings where the installation of ducts would not be possible.

The downside to ductless systems can become apparent in geographic areas that experience particularly cold winters. The units are often ill-equipped to handle the extreme cold, forcing a reliance on electric back-up heating which is typically more expensive to operate than combustion appliances such as natural gas.

Measuring Efficiency

There are two metrics you should know in order to best understand the efficiency of proposed HVAC solutions:

Seasonal Energy Efficiency Ratio (SEER)/ Energy Efficiency Ratio (EER): ratio of energy to cooling capacity at a specific temperature.
Annual Fuel Utilization Efficiency (AFUE): ratio of fuel supplied to furnace to the amount of heat delivered to space.

Obviously, the prior is used to measure cooling optimization, while the latter measures heating only. Combined, these metrics allow you to best gauge the effectiveness and efficiency of your options.

Alternative Options and Tax Credits

Of course, the two solutions described above are not the only alternatives you have for an HVAC solution. To learn more about energy efficient options not only for your heating and cooling system, but also for appliances, building products, electronics and lighting components, visit the Energy Star products for the home page. This federally-approved program has tested all the products that carry the ENERGY STAR label to determine that they assist in reducing greenhouse gas emissions through energy efficiency without compromising performance, comfort or features.

You can also learn about available federal tax credits for energy efficiency modifications and products in your home on the Energy Star site, as well as the Database for State Incentives for Renewables and Efficiency in the U.S. website (DSIREUSA) which has a state by state list of tax incentives, including tax credits and deductions, if they are available in your area. Central AC split systems must be a minimum of SEER 16 and EER 13. Gas-fired furnaces must demonstrate an AFUE of 95% or more.) However, it’s always a good idea to confirm your understanding of these solutions and tax credits with multiple quotes from local HVAC contractors. And, no matter what, before you’re moving forward, be sure to acquire the Manufacturer’s Certification Statement for the equipment you plan to purchase.