Demand response California: Pepco EV owners show flexibility

US utility Pepco’s electric vehicle charging pilot shows how demand response events can influence customer behaviour.
Published: Tue 14 Mar 2017

When compared to California’s more than 100,000 electric vehicles (EVs), Maryland’s 7,000 is a drop in the ocean. But, the state would like to increase this to 60,000 EVs which is supported by the eight-state agreement which wants 3.3 million EVs on the roads by 2025.

The agreement hopes to plan infrastructure changes that will incentivise consumers to buy zero-emission vehicles.

The plan includes changing building codes to make it easier to create EV charging stations. The states also hope to offer financial incentives to zero-emission vehicle drivers, including reduced electrical rates for those who charge cars at home.

Several of the participating states of California, New York, Massachusetts, Maryland, Oregon, Connecticut, Rhode Island and Vermont have already adopted their own rules regarding zero-emission vehicle sales, but the new agreement hopes to coordinate efforts between them. Together these states account for 23% of the total automobile market.

The increase in vehicles will need the appropriate infrastructure and Maryland has been hard at work putting this in place.

Significant investment has been ploughed into statewide charging, including hundreds of public stations according to an action plan, passed by the multi-state task force. The state also passed legislation to extend a popular tax credit, expanding it to provide $125/kWh of plug-in vehicle (PEV) capacity.

EV charging and grid flexibility

Although public infrastructure has grown significantly, EV owners continue to do most of the charging at home which could eventually lead to the overloading of residential transformers. A pair of Level 2 chargers generate load equivalent to about the size of a home so it wouldn't take long for clustering to develop some issues, according to Rob Stewart, Pepco’s smart grid and technology manager.

To accommodate the growing demand from EVs, electricity provider Pepco conducted a two year pilot programme (2013-2015), which involved the integration of EV charging to its demand response (DR) portfolio. The aim was to find ways to manage assets more efficiently so that demand could be shifted from peak to off-peak consumption periods.

The pilot highlighted many useful points such as that customers are actually willing to pay for cleaner electricity and are happy to participate in DR programmes. Also, over 90% of participating customers changed their consumption behaviour once they were exposed to different rate structures.

Rate structures-giving customers the choice

Pepco signed up 101 customers in the pilot to which two different rate structures were offered: A time of use (TOU) rate applying to the entire household, including EV demand (whole-home rate). Fourteen customers were enrolled on this rate. The other rate involved the EV alone to which 87 applied.

With the whole-home rate, consumers know what they are getting but if their lifestyles demand energy during peak times, rates can be costly.

However with the EV-specific rate, peak charging times ran 12 noon to 8pm from Monday to Friday at a rate of about 23 cents/kWh. Off-peak rates dropped to 5 cents/kWh.

According to Pepco, the difference in rates was enough to shift demand, and the utility estimated a Volt or Leaf driver could save about $300/year charging off-peak. A review of the pilot reveals that using the average residential electricity price and average EV miles/kWh, EV power costs the equivalent of $1/gallon (3.8 litres) compared with the current $2.29/gallon (8.66 litres).

Within the EV-only rate, a "green rider" was introduced by Pepco. Over 30 consumers opted for this option which allowed them to pay $2 cents/kWh extra for their energy. Pepco would acquire and retire corresponding renewable energy credits, and in return drivers could claim zero tailpipe emissions. About 30% of customers in the EV-only rate opted to pay slightly more for the cleaner power.

Demand response California - pilot results

A report on the study, conducted by the Electric Power Research Institute, revealed interesting individual model data: On average, vehicles were charged less than once a day, consuming 8.36kWh per day.

According to the study, the pilot programme revealed that EV customers, regardless of vehicle type, mostly charged at off peak charging times, confirming that TOU rates are an effective way of shifting load off peak.

Furthermore, almost no customers were charging during demand response events which shows that just planning a DR event incentivizes customers not to charge during that time or that customers were not plugged in at that time anyway.

"Of the top three vehicle types (Tesla, Volt and LEAF), Volts charged the most often and Teslas charged the least often," the report found. Teslas averaged 11.49kWh/d consumption, while Leafs and Volts were lower, at 7.34kWh/day and 6.25kWh/day, respectively.

The pilot used smart chargers with Itron meters, which worked alongside the utility's AMI for the charge point.

However, there were some technology issues. When both meters were properly logging data, the Itron and AMI meters were within 2% of one another (the Itron meter included revenue-grade equipment installed in the smart charger).

However, EPRI's report concluded that "due to communication issues, Itron meters did not log many of the charge events (over 70%)." Wi-Fi and software problems were to blame for the miscommunication, according to the report.

Despite the metering problems, Pepco reported that the DR programme was successful. The utility said that during days when there was a need for curtailment, charges were turned down from Level 2 to Level 1 capabilities for an hour only.

Successful demand response events

Pepco deployed 50 smart chargers. Customers were able to opt out of events through the use of a phone app or button on the charger. These decisions gave Pepco data on customer preference which could be used to optimise grid management.

During the pilot, the utility planned seven DR events. The utility said that the responses showed how flexible customers can be during these events. The success of these events is more than likely due to the fact that the utility gave fair warning of them (a few hours) and customers were able to adjust their consumption behaviour accordingly.

Based on the success of the EV-only rate, Pepco aims to make it a permanent fixture.

Pepco plans for a big EV future

While Maryland’s load shifting is small in comparison to other states, significant growth is expected to occur especially since the region overlaps into the Washington, DC-Northern Virginia corridor. While public chargers will encourage interest, it is believed that EV owners will continue to charge their vehicles at home.

By moving EV charge off the TOU rate, 3kW per vehicle is being shifted. This will certainly make a big difference as the market gains momentum.

The utility spent about $0.5m on the pilot, with the largest portion being spent on programme management. 

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