New York City’s benchmarking data now spans six years, showing significant declines in large-building energy use and greenhouse gas emissions between 2010 and 2015. Over that period, emissions from more than 4,200 regularly benchmarked properties fell by almost 14 percent, while energy use fell by more than 10 percent.

This is encouraging news. While these six years imply a promising trend, there is still much work to be done in order to reach the City’s goal to reduce greenhouse gases 80 percent by 2050. Future reductions will be tougher to achieve, since half of these declines are due to a cleaner electrical grid and more efficient district steam generation. Building owners will have to dig deeper into energy efficiency to keep up the pace now that most electricity generation from coal and oil has transitioned to natural gas and renewables in New York State.

It is difficult to know whether these large-building declines reflect a general trend in existing buildings of all sizes. The Greener, Greater Buildings Plan (GGBP) benchmarking requirement applies only to buildings 50,000 square feet or larger. This is about 47 percent of New York City floor space, or roughly 2.3 billion private square feet, and another 450 million municipal square feet. However, more data is on its way. Last year, the GGBP was expanded to include buildings 25,000 square feet and larger by 2018, adding another 340 million square feet into coverage. Come 2019, we will be able to report on nearly 60 percent of New York City’s square footage. That’s a stunning achievement for the largest city in the country—a city of an approximated (and mind-boggling) 1 million buildings.