A study done for electric utility Southern California Edison finds that with a market share of 10%, the combination of electric vehicle (EV) batteries and managed overnight charging can provide a virtual power plant that completely shaves residential peak demands.

The study analyzed data on 5,000 SCE utility customers including each customer’s hourly loads, commuting data and battery reserves after afternoon commuting. It then simulated the ability of a virtual power plant (VPP) to clip the residential sector peak demand while also constraining EV overnight recharging to avoid an overnight peak.

A 10% penetration level could entirely shave residential peak energy demand.Financial benefits were estimated to be an annual cost savings of $560 per EV customer even after accounting for the cost of overnight EV recharging. The report said that expected growth of the EV market, along with the benefits of even a limited EV market saturation, "highlight the urgency of developing appropriate utility programs, EV technologies and a supportive regulatory framework."

The report was prepared by Jerry Jackson, president of the consulting firm Jackson Associates, which advises utilities and technology companies on market analysis, sales and market strategy for a variety of new energy technologies.

Assumptions

For the analysis, the SoCalEdison EV time-of-use rate period differentials were applied to estimate cost savings. Utility cost savings for each kilowatt-hour (kWh) shifted from on-peak to off-peak was approximated as the differential in those two rates. Shifting one kWh from the 4 to 9 pm on-peak time period to off-peak hours could save $0.25 in the summer and $0.23 in the winter, the study said. Weekend savings were not considered because weekday commuting savings were expected to be significantly greater than potential weekend savings.

In addition, the study assumed that utility load management would access reserves still left in the EV battery after the afternoon commute, reserving at least 20% of the full battery charge (equaling roughly 60 miles of driving) for evening travel.

The analysis also assumed a level 2 home charging station with a charging demand requirement of 10 kilowatts with a full charge requiring 9 hours providing a 300 mile range.

Households with more than $125,000 in income and with total daily automobile commutes of less than 120 miles were selected to represent future EV owners. EV ownership was randomly assigned to households who used private automobiles to commute.

Wider applicability

The report said that its analytic approach can be extended using utility customer hourly loads, household and commuting data for a sample of all customers in a utility service area and actual utility service area cost of service. Geographic detail also can identify substations and feeders most likely to benefit from an actively managed virtual power plant strategy. And scenario analysis can provide business case results to reflect alternative EV characteristics as well as saturation and program assumptions.