EPRI's 'HotSpotter' Tool: Identifying potential utility system overloads in a growing EV market

The current wave of Plug-In Electric Vehicles (PEVs) entered the market in late 2010. As of February 2016 there were 24 models of PEVs on the market and cumulative sales in the U.S. reached over 400,000 vehicles. Between the rapid pace of PEV technology development and concerns about global warming, the market for EVs is expected to continue expanding and diversifying, even though current low gasoline prices may affect growth rates. Typical residential charge rates vary from as low as 1.4 kW for Level 1 (120V) to as high as 19.2 kW for Level 2 (240V). Battery capacities vary from a low of 5 kWh to a high of 90 kWh with a range upwards of 270 miles. Battery prices fell 35 percent last year and are on a trajectory to make unsubsidized electric vehicles as affordable as their gasoline counterparts in the next six years, according to a new analysis of the electric-vehicle market by Bloomberg New Energy Finance (BNEF). That will be the start of a real mass-market liftoff for electric cars. By 2040, long-range electric cars will cost less than $22,000 (in today's dollars), according to the projections. EPRI anticipated this market growth and launched a Phase 1 study of EV impacts on electric utility distribution systems in 2012. A Phase 2 study was launched in 2014 to develop a screening tool utilities could use to gauge system impacts and mitigation strategies. Functionalities include: • The ability to assess load risks to service transformers for multiple potential PEV scenarios; • Account for geographic clustering and variations in PEV characteristics across the utility system • Quantify the overall risk to system assets using the utilities' existing transformer database • Incorporate planning and business practices necessary to estimate cost impacts and potential mitigation strategies. This paper details this screening tool developed by EPRI and provides a case study developed in collaboration with the Sacramento Municipal Utility District using actual distribution system data.