Time and Motion Study for Solar Contractors

Abstract

One of the main goals of the solar energy industry is making solar technologies cost-competitive with other forms of energy. In particular, balance-ofsystem (BoS) costs associated with the installation of photovoltaic (PV) systems require significant cost savings to stay competitive with conventional energy sources. Significant potential for cost savings exists through increasing the productivity of the labor force installing the system. A gap in knowledge exists regarding approaches to measuring and improving solar installation labor productivity. The objectives of this research are to design a proper method for conducting time and motion studies for solar contractors, collect and aggregate data related to installation practices, and examine factors that affect solar installation labor productivity. In order to achieve these objectives, the Georgia Technology Research Institute (GTRI) laboratory, in partnership with the Rocky Mountain Institute (RMI), conducted time and motion studies on residential and commercial projects sites to collect and document data on the steps in the installation process of PV systems. An aggregation and analysis of data recorded for each step in these studies was performed to estimate the time to accomplish each task and identify the patterns that affect labor productivity. For this research, the proposed time and motion study approach was examined on two residential and commercial solar installation projects. The findings of the research show that conducting proper time and motion studies can determine the time spent on solar PV installations activities, in order to better understand which activities consume the most labor time and what types of contextual variables have greater impacts on installation labor productivity.

Observations and Lessons Learned From Installing Residential Roofing-Integrated Photovoltaics

“…• Flashing and PV system installation is the most time-intensive stage of the RIPV installation process. PV system installation and flashing accounts for around 60% of the installation process for an average system and is consistent with the findings of Quintanilla et al (2014) for conventional systems.…”

“…• Our time and motion results suggest that RIPV systems can be installed more quickly than conventional rooftop PV systems due to synergies with reroofing and new construction. The average total process times in our study were 6.4 and 3.5 worker-hours per kW for the reroofing and new construction sites, respectively, compared to an estimated 6.9 worker-hours per kW for conventional, retrofit residential rooftop PV from a previous study (Quintanilla et al, 2014). However, that study was completed in 2014, and a more recent analysis is necessary to ensure that installation times are still comparable.…”

“…Figure 6 generates two findings that are worth further exploration. First, most of the analyzed complexity variables do not significantly affect installation times, in contrast to the hypothesis from Quintanilla et al (2014) that project complexity likely increases installation times. While it is possible that such impacts could be measured in larger statistical samples, our analysis suggests that crews efficiently navigate these complexities.…”

“…The literature and interviewees suggested that PV system layout may affect installation times (Quintanilla et al 2014). To evaluate the impacts of system layout and other factors on installation times, we tracked the number of home stories, PV roof planes, and subarrays, as well as array shape(s) for each observation.…”

“…The only comparable time and motion study of conventional retrofit solar, to our knowledge, is the analysis presented in Quintanilla et al (2014). 17 The comparison in Figure 7 is based on timelines for solar installation processes.…”