Many of us are working hard to make our homes more energy efficient. Many of us, however, may not have a clear target to strive for. We want more efficiency, but what’s considered “energy efficient” for a home?
NRCan explains the features of an energy-efficient home. It says energy efficient homes are cost-effective, “well insulated and airtight,” comfortable, healthy and “[k]ind to the environment.” These features are well worth pursuing, but they’re also a bit relative.
And if we’re always looking to improve energy efficiency and lower our footprints, how will we know when we’ve done the most we can with the home we have?
Most of us are probably looking to our utility bills to figure out if an upgrade or retrofit has resulted in a better performing home. Bills can be misleading, however, since everything from the weather to the amount of time we spend in the home impacts those bills.
Unless we’re doing some deep monitoring, it can be hard to know for sure whether it’s an improvement in home performance or a change in behaviour that’s making the difference.
To know whether our efficiency upgrades are paying off, we need a baseline to start from and a benchmark to aim for.
A DIY Approach to Determining Energy Efficiency
Allison Bailes of Energy Vanguard has a simple energy efficiency scale that you can use to estimate how efficient your home is. All it requires is a year’s worth of energy bills and a little math.
Get the Green Building Project Checklist
Use this handy checklist on your next project to keep track of all the ways you can make your home more energy-efficient and sustainable.
Bailes’ method is to take all your energy bills for the past 12 months and from them, “find out how many kilowatt-hours of energy you used for those 12 months.” Then you divide that number “by the square footage of conditioned floor area” (i.e., the square footage you’re heating and cooling).
The resulting number, Bailes says, “will almost certainly be between 1 and 30 kilowatt hours per square foot per year.” The scale he uses puts that number in perspective:
- 0 – 5: Super efficient
- 5 – 10: Efficient
- 10 – 15: Moderate
- 15 – 20: Bad
- > 20: Energy Hog
Using this knowledge as a baseline, you can then do your own home energy audit. You can think through the particulars of your home’s energy use to start to make your home more efficient.
There are a lot of factors to consider. You can determine how much insulation you have, how leaky your windows are, how old your appliances are, how energy-conscious you are in your living habits, and so on. The U.S. Department of Energy has a resource on DIY energy assessments here.
Energy Evaluations and Standards
Aside from a DIY approach to figuring out what’s considered energy efficient for a home, there are professional ratings scales that offer their own, more detailed baselines and targets.
EnerGuide Ratings Scales
Houses that went through EnerGuide home evaluations prior to 2019 will have a rating based on a 0-100 scale. On this scale, 0 represented the worst possible rating and 100 represented a net-zero home.
According to NRCan, an existing house was energy-efficient if it rated between 66 and 74. New energy-efficient houses rated between 81 and 85. Houses that rated higher than 85 were considered high-performance houses.
Those reports are still around and can still be used to share information about a home’s energy performance at the time it was evaluated.
The new EnerGuide rating system is consumption based. Now, homes that have completed an EnerGuide evaluation are issued a label that rates a home by estimating how many gigajoules of energy it uses per year and placing it on a scale from most to least efficient. The lower the number, the more efficient the home.
The calculations are based on standardized usage, eliminating occupant behaviour from the equation and measuring how much energy it takes to operate the house under standard conditions.
There’s no set number at which a home becomes energy efficient on this scale. For reference, Énergie et des Ressources naturelles Québec suggests that the “average Canadian household uses 100 gigajoules of energy per year.” The benchmark EnerGuide offers is to compare an existing home’s energy use to what that home would use if it had been built to today’s building codes.
HERS Index
Like EnerGuide, the HERS (Home Energy Rating System) Index is a report issued after a third-party evaluation of a home’s energy efficiency. It indicates the home’s energy performance on a scale from 0-150.
The lower the score here, the better, with net zero homes at zero and energy guzzlers at 150. Homes are compared against a “reference home,” an imagined model built to standard building codes and similar to the home being evaluated in terms of size, climate region and other factors. The reference home has a score of 100. An energy efficient home comes in at 90, while a “good” score is a 70.
High-Performance Ratings Systems
There are ratings systems for high-performance homes, as well. Homes that receive any of these certifications will be extremely energy efficient.
Homes that have been certified through ENERGY STAR will be 20 percent more energy-efficient than homes built to standard building codes (on average). R-2000 homes are on average 50 percent more efficient. LEED homes are 20-30 percent more efficient than code, although that number can climb considerably depending on the level of certification a home receives.
The most energy-efficient standards are Passive House, Net Zero, Net Zero Energy Ready and Living Building. If energy-efficiency is the absolute top of your list, these are the highest standards to strive for.
Energy Conservation
Back in 2010, Allison Bailes cautioned us that there’s an important and really underplayed difference between energy efficiency and energy conservation. He says that by and large, we’ve “gotten more energy efficient without conserving energy.”
“Since 1980 our primary energy use has stayed constant,” he notes. Homes use less energy than they used to, but since homes have gotten bigger and families have gotten smaller, we weren’t consuming any less energy in 2010 than we did in 1980.
That tracks with NRCan’s findings that between 1990 and 2013, energy efficiency increased by 45 percent in the residential sector, but energy use actually went up 6.5 percent. Without those efficiency improvements, they state, energy use “would have increased 51 percent.”
Which is all to say that lowering consumption should be a key part of an energy-efficiency strategy. If given the choice between a larger, newer home in the suburbs and a more modest home close to public transport, the smaller home will be the clear winner when it comes to energy use.
