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Ex Post Evaluation of the Empire State Building Retrofit

The Empire State Building is the tallest and most well-known building in the United States to have received LEED certification. The certification was part of a massive retrofit undertaken between 2009 and 2011. Engineering models predicted that the retrofit would reduce the building’s energy use by 38 percent, saving $4.4 million annually (NYT, 2009). The project has received an enormous amount of attention. See, for example, this Newsweek article here.


And what makes me extremely happy about this project is that data are being made available for ex post evaluation. The latest report from Johnson Controls is available here. Most of the report describes simulated energy consumption generated using an engineering model of building performance. But the report also includes data describing the building’s actual energy consumption.



These figures plot monthly electricity and steam consumption. Most of the retrofit was completed between April 2009 and October 2010, so these comparisons between 2007 and 2011/2012 provide a before and after comparison. The comparisons across warm and cold months are also interesting because many of the investments were aimed at the building’s shell (e.g. windows, wall insulation, etc.), so these comparisons can shed light on which particular elements in the retrofit were most effective.

The results are impressive. Electricity consumption decreases 29% during winter months, with even larger decreases during summer months. Most tenants in the Empire State Building are individually metered for electricity, so these savings are accruing primarily to tenants themselves, and to the building’s owners through increased rents. Steam consumption also decreases, though these data are considerably more variable. Total energy expenditures for the Empire State Building reach $10 million annually for electricity and $2 million annually for steam, so these reductions correspond to millions of dollars in annual savings.

As more years of data become available it will be important to continue to refine these estimates.  Additional data from 2008, 2009, and 2010 would add value, as would analysis of subsets of tenants who received different elements of the retrofit. The Empire State Building retrofit has already been an influential project because of its size and scope. It can also be an influential project in terms of ex post evaluation, illustrating how usage data can be used to document best practices in large building retrofits.

Lucas Davis View All

Lucas Davis is an Associate Professor of Economic Analysis and Policy at the Haas School of Business at the University of California, Berkeley. His research focuses on energy and environmental markets, and in particular, on electricity and natural gas regulation, pricing in competitive and non-competitive markets, and the economic and business impacts of environmental policy.

8 thoughts on “Ex Post Evaluation of the Empire State Building Retrofit Leave a comment

  1. Do the savings include occupancy sensors to shut off lights that are not used? Are the outside decorative lights on this building on 24/7? How is hot water for this building heated? Is heat recovered from waste water? 39% is impressive but there is so much more!

  2. In interesting article but I wanted to immediately calculate the kwh per person who works there per day to see how energy efficient high rise buildings are. This is not possible at the Y axes of these graphs is not in units of energy per time, and thus meaningless except for comparison purposes. Is it possible to re-label the graphs with kwh/day? Also to make sure no businesses leaving the building have made a difference, a much better measure would be kwh/day/person. As a scientist I would also like to see steam in kwh/day/person as otherwise absolute energy consumption is hard to calculate.

    I am interested in this as I have “heard” that high rise buildings actually use surprisingly large amounts of energy per person because of the continuous ventilation requirement 24/7 which uses a large amount of power per person. Does anyone have any data on this?

    Also payback period for retrofit. Was it worth the capital cost?

    • I should have been clear. These figures are taken, as is, from the Johnson Controls report. The description of these figures in the report is a bit vague, but I am pretty sure these are monthly observations, so you could scale the y-labels by 1/30 to get energy consumption per day. And yes, payback period would be extremely interesting. See my responses to Rudnick and Rumble above.

    • I haven’t seen a careful description of the retrofit costs, though one may well exist. The NYT reported in 2009 that the retrofit project would add $20 million to the $500 million building makeover (NYT, 2009).

  3. What is the ROI? The raw numbers are impressive but certainly less important than the return. This is not the way to present a report.

    • I’m not sure. This has been such an influential project that it would great if someone would do a careful analysis of the return. Perhaps someone has already done this analysis, but I am not aware of it. First step would be to carefully measure the retrofit costs. This is especially difficult in this case because the energy-efficiency investments were part of a much larger retrofit. As I mention in a response below, the NYT reported in 2009 that the retrofit project would add $20 million to the $500 million building makeover.

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