A 1999 Pacific Gas & Electric Company (PG&E) daylighting study analyzed a retail chain of 108 stores where two-thirds of the stores were lit with skylights and one-third were not. All other things being equal, the study found that the daylighted stores had 40% higher sales than those without.
(Heschong Mahone Group HMG “Skylighting and Retail Sales” Report at www.h-m-g.com, 1999)
In 2003, a new retail study was conducted to replicate the HMG study with a new (anonymous) retailer. The report stated:
-However, the more detailed “daylight hours per year” model found that there was a significant
dose/response relationship between the number of daylight hours per year and the magnitude of
the increase in sales (once other factors, such as the size of the parking lot, were considered).
-Daylight was found to be as reliable a predictor of sales as other more traditional measures of retail potential, such as parking area, number of local competitors and neighborhood demographics.
-During the California power crisis of 2001, when the chain operated its stores at half-lighting
power, the daylit stores had an average 5.5% increase in sales relative to the non-daylit stores.
-Along with an increase in average monthly sales, the daylit stores were also found to have a 1% to 2% increase in the number of transactions per month.
-Stores with the most favorable daylighting conditions had a 40% increase in sales compared to
non-daylit stores, consistent with the findings of the HMG study.
-No seasonal variation was detected. Researchers concluded this suggested a long-term customer
loyalty effect and not a short-term impetus on sales.
(“Integrated Energy Systems: Productivity and Building Science” report prepared for the California Energy
Commission Public Interest Energy Research Program by the New Building Institute Inc., October 2003)
In relation to the original PG&E study, the link between high consumer activity and skylighting occurs despite the fact that many of the customers interviewed state that they were unaware of the presence of skylights. Rather, the customers responded that they frequent the skylit stores because of non-specific positive environmental feelings, such as that the stores feel cleaner, more spacious, more open or brighter. The authors of the study offer several hypotheses concerning why the skylights encourage these sentiments, including:
-Customer Loyalty – Although they are unaware of the skylights, customers may routinely travel a little farther to shop at a skylit store because it seems cleaner or brighter
-More Relaxed Customers – The skylights may impact customers in a manner similar to piped-in
music, which has been found so effective at relaxing customers and encouraging them to spend
more time shopping in the store
-Better Visibility – It may be easier for customers to find products and/or discriminate between
alternatives with daylight illumination
-More Attractive Products – It is possible that visual quality provided by daylighting, with high color rendition and three-dimensional modeling, may make products more appealing
-Employee Morale – It could be that employees working under natural light have higher morale and provide better service as a result
(Houston Business Journal, September 22, 2000)
A 1995 Wall Street Journal article reported Wal-Mart’s experience with daylighting its store in Lawrence, Kan. Sales were significantly higher in the side of the store that utilized skylights than the same products displayed at other Wal-Mart stores. To test the correlation, products were swapped from the artificially lit to the daylit sections and those located under the skylights again had significantly higher sales while those shifted to the artificial lights returned to their national sales average.
