Diane asks: We are remodeling and want to improve energy efficiency. We are improving insulation and also replacing heater. We are debating merits of Mitsubishi Comfort— electric vs gas heat. How do we go about comparing efficiency of electric and gas heat?
Thanks so much for your question. Let’s dive into discussing the pros and cons of both electric vs gas heat.
It sounds like you’re in need of a home HVAC system in an area that still has a cold climate (based on the mention of the gas furnace). So what I’ll be comparing and contrasting here are two systems: Central AC with a gas furnace (probably the most common home HVAC system) versus a ductless AC multi-zone system with electric heat. Comparing electric vs gas heat may seem like a daunting task, but we have the answers for you here!
Electric vs Gas Heat Options
Gas Heat Pros and Cons
- Price: The upfront price of a gas furnace is much more expensive than that of an electric heater. The daily price of generating heat with a gas furnace ultimately costs less, though.
- Effectiveness: Gas furnaces heat your home more quickly than electric heaters.
- Maintenance: Unfortunately, gas furnaces require more maintenance. They also typically don’t last as long as electric heaters.
- Health Risks: Since gas furnaces give off a small amount of carbon monoxide, it is pertinent to your family’s health that you ensure the unit is always operating properly. Keeping a closer eye on the unit might be worth it for the lower monthly heating bill.
Central AC with Gas Furnace
If we are comparing electric and gas heat, the first option is relatively simple and more familiar. A furnace located in the basement circulates warm or cold air throughout the house via a series of ducts and registers. This air is then returned to the furnace via more ducts and grilles. A gas-fired heat exchanger in the furnace provides heat, and a DX cooling coil (coupled to an exterior condensing unit) provides cooling. A single thermostat controls the furnace, so all rooms in the house are heated or cooled similarly.
Electric Heat Pros and Cons
- Price: The initial price of an electric heater is less than that of a gas heater. However, the cost of running an electric heater is more expensive in the long run.
- Effectiveness: While installing electric heaters is less time consuming, the overall heating process takes longer. In other words, when you turn up the heat, electric heaters take longer to adjust and raise temperatures accordingly. Electric heaters are generally quieter while running, though.
- Maintenance: Electric heaters last anywhere from 20 to 30 years and require minimal upkeep.
- Health Risks: If you’re experiencing any mechanical issues with your heater, getting them checked out by a professional is essential. However, in the event that your electric heater has a hiccup, the health risks are much less than those associated with malfunctioning gas furnaces.
Ductless AC Multi-Zone System with Electric Heat
These systems aren’t as widespread in the US as they are in other parts of the world. Indoor heat pump units are located in several rooms throughout the house. These units include a fan and cooling/heating coil and can be supplied with electric back-up heat in some instances. Typically for every three indoor units, you have an associated outdoor unit. This condensing unit is smaller than the one coupled to the more traditional system option (the first option described above) and typical dimensions of 30”x35”x12” wide coupled with a rectangular shape.
Each indoor unit is controlled by its own thermostat, so different spaces could have different set-point temperatures. Since ductless mini-splits have no ductwork, they don’t experience the energy losses associated with air transmission in central forced-air systems. However, during exceptionally cold winter months, the heat pump will likely not be able to keep up with heating demand, and would need to be supplemented with electric heat. And while electric heating converts electricity directly to heat, it is often more expensive than heat produced by combustion appliances like natural gas.
SEER and AFUE
Seasonal Energy Efficiency Ratio (SEER), is most commonly used to measure the efficiency of a central air conditioner over an entire season. Energy Efficiency Ratio (EER) is a measure of how efficiently a cooling system will operate when the outdoor temperature is at a specific level (95°F). Both SEER and EER are simply a ratio of energy in to cooling capacity. Therefore, the higher the SEER or EER, the more efficient the system. On the heating side, annual fuel utilization efficiency (AFUE) is a measure of a furnace’s heating efficiency, in amount of fuel supplied to amount of heat delivered to the space, so higher AFUEs are also preferable.
Aware of Climate Differences
For those in colder climates, gas heat is more than likely the best way to go. Gas furnaces heat the home more quickly, and in a colder area you are dependent on your heater to ensure your comfort. Assuming you are correctly maintaining your unit, it will last longer and be safer for your family.
However, for those in warmer climates, electric heat may be the more attractive choice. Since you aren’t as dependent on quick working heat, you don’t need a gas heater. You don’t have to dedicate as much time to maintaining your unit, and it will still last a long time.
In terms of overall efficiency, both electric and gas heat systems could be quite economical and environmentally friendly if properly designed. To further complicate your options, instead of just a split system for cooling, a traditional gas furnace could be supplied with a heat pump for added energy benefits.
If you’re looking to make easy, energy-efficient choices for your home, the Energy Star website would be a great place to start. You can search for Energy Star products for the home, including appliances, building products, electronics as well as HVAC equipment, lighting and plumbing components.
All of this equipment has earned the Energy Star label by demonstrating that it helps reduce greenhouse gas emissions and other pollutants through energy-efficiency without sacrificing performance, features, or comfort.
Also, on the Energy Star website, you can find information about federal tax credits for energy efficiency which you can use to help set targets for your new equipment’s efficiency. For central AC split systems (which both of your options could quality for) must be a minimum of SEER 16 & EER 13. Gas-fired furnaces must have an AFUE of 95% or greater. The best way to find out what tax credits are available and to compare system costs and energy savings is to get several quotes from a local HVAC Contractor.
To verify tax credit eligibility, make sure the contractor provides the Manufacturer’s Certification Statement for the equipment you plan to purchase.
Taking all of this into consideration, aside from the type of climate you live in, you have to decide which points concern you the most. Are you more worried about initial or overall cost? Are you okay with committing to some extra maintenance if it means you can heat your home for less? Ultimately, it really depends on your preferences. There’s no hard and fast rules for which type of heat is best.
Sarah Gudeman is a mechanical design engineer and licensed EIT in the state of Nebraska. Ms. Gudeman also is a LEED Accredited Professional (BD+C) and an active member of the USGBC Nebraska Flatwater Chapter’s board of directors. She specializes in building energy modeling and audits, sustainable design and environmentally-friendly practices.
Kristen is a writer for Poplar Network.