Metered New York now includes data from 2014 — and we think it’s pretty exciting. Energy Star scores have been available for offices since 2011, but 2014 added these scores for multifamily buildings. For the first time, we can see how New York’s large residential buildings compare against other similar buildings nationally.
ENERGY STAR in Multifamily Buildings
Building consumption can be gauged on energy use intensity (EUI) which tells us how much energy per unit area is needed to heat, cool and power a building. But what if one multifamily building is more densely populated than another? It will probably have a higher EUI than a high vacancy building, but that doesn’t mean that the densely populated building performs poorly. Similarly, a building in California will probably have a lower EUI than one in New York because of our colder winters and humid summers.
To address these differences and make energy efficiency more comparable, the Environmental Protection Agency (EPA) introduced the Energy Star (ES) rating system for commercial buildings in 1999. A building is given a score scaled from 1 to 100 to represent its energy efficiency relative to comparable buildings across the country. This score incorporates location, size, energy and usage into a calculation that ranks the building against its peers.
Figure 1: Distribution of Energy Star scores for NYC multifamily buildings in 2014
In this data set, almost 6,000 multifamily buildings submitted enough energy, occupancy and operational data to calculate an ES score. This represents two-thirds of the total multifamily buildings that benchmark. New York City’s median multifamily score in 2014 was 55. The scoring of multifamily buildings is still new, so New York is one of the few cities with published data. But nationally there are enough multifamily buildings in the EPA database to create the ES scale and set the median at 50, so NYC is performing slightly better than the national average.
Consider the ranges in the table below to understand how the ES score translates to energy consumption. Multifamily buildings with an ES score from 1 to 25 had a median weather-normalized source energy usage intensity of 174 thousand British thermal units per square foot (kBtu/sf/year). Those that scored from 76 to 100 had a median intensity of 92 kBtu/sf/year. This means that every year the worst performing multifamily buildings consume almost twice as much energy as the best performing buildings – based on the Energy Star scale.
Does benchmarking lower energy consumption?
There are many drivers for lowered energy consumption in buildings, but we do know that NYC’s consistently benchmarked buildings realized 6% total energy savings and 8% carbon savings from 2010 to 2013. Our hope is that Energy Star scores will communicate building energy efficiency more clearly, and perhaps they will help us understand these reductions in energy consumption.
We are conducting research to discover the drivers of these savings. For example, is New York City's fuel switching program causing the difference between the drops in energy and emissions? What role do factors like facility manager training and building owner engagement play?
Stay tuned to find out the answers as we work with New York City and NYU CUSP to analyze all the data coming from Local Laws 84 and 87. For now, dive into Metered.nyc to see how the buildings you work and live in use our energy and water resources.
We’re also eager to see if the energy and emission reductions seen in the first four years of the program have continued. We’ll be running through the rest of our data cleaning and analysis to report the findings later this year. Check out New York City’s Energy and Water Usage Report to see last year’s results.