an events-based approach to low-carbon ev charging

An events-based approach to low-carbon EV chargingSilicon Valley Clean Energy&ev.energy June 2021

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Silicon Valley Clean Energy (SVCE) is a community choice aggregator (CCA) serving 13 communities in Santa Clara County, California. With a customer base of over 240,000 residential customer accounts, SVCE has seen rapidly increasing levels of EV adoption with approximately 25,000 EVs on the road in its service territory as of January 2020. Over 20% of SVCE's residential customers are enrolled in time-of-use (TOU) rates, with the remainder of customers still on flat rates set to be migrated to TOU over the course of summer 2021. SVCE's rates have off-peak pricing generally beginning after 9 p.m. and continuing through the morning hours, with some more recent rates (e.g. EV2-A)

continuing off-peak periods until 3 p.m. the following day. Due to the nature of California's generation mix, the California grid tends to be relatively higher-carbon during evening and overnight hours, when gas-fired power plants complement baseload nuclear, hydro and geothermal, while daytime hours tend to be characterized by excess solar generation that is often curtailed due to lower demand, resulting in a net load profile known as the "duck curve" (Fig. 1).

An events-based approach to low-carbon EV charging (SVCE & ev.energy)

Introduction & overview

Figure 1: Net load on the California grid on a typical spring day. Source: California Independent System Operator (CAISO)

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As seen in Figure 1, the California grid is strained by excess solar generation during daytime hours (mainly between 10 a.m. and 5 p.m.), yet residential customers are generally incentivized by TOU pricing to consume energy overnight or in the early morning - including charging their EV. However, the COVID-19 pandemic and resulting shelter-in-place orders resulted in a profound shift in lifestyle patterns, energy consumption levels, and EV charging behaviors. With many customers tending to work from home in 2020 and 2021, EV drivers were staying plugged in for longer, including during the daytime hours. As seen in Figure 2, data from the ev.energy platform showed that while the most common plug-in time shifted only one hour from 5 p.m. in January 2020 to 6 p.m. in January 2021, the most common unplug time for an EV driver shifted from 8 a.m. to 3 p.m. over the same period. The result of this was an increase in the average duration that an EV remained plugged in while parked at home from 12.2 hours in January 2020 to 20.2 hours in January 2021: effectively, a shift to working from home nearly doubled the length of the window during which a charge could be delivered to the vehicle.

SVCE sought to take advantage of this increase in flexibility by incentivizing EV drivers to shift their charging to lower-carbon daytime hours, given that customers were tending to stay plugged in later into the day. SVCE had already launched a telematic EV charging pilot with managed-charging software company ev.energy, which deployed a mobile app to participating customers that they used to track and manage their EV charging at home. Using the GridShift app, an SVCE customer would be on-boarded using tariff and other information available through SVCE's Data Hive powered by UtilityAPI, and would be able to wirelessly connect to their vehicle using telematics. The customer could then select a departure time for their vehicle, plug in, and have their EV automatically charged during off-peak hours on their rate plan. Between November 2020 and February 2021, participating customers saved an average of $24 per month on their energy bills vs. charging immediately upon plug-in. As spring 2021 approached and the duck curve became more pronounced, SVCE began to explore new ways to incentivize EV charging in the "belly" of the duck, while ensuring that customers' energy bills continued to decrease through the GridShift program. Seeking to further shift EV charging loads to optimal grid times, SVCE planned a suite of new features for the GridShift program that would nudge customers to plug in before hours-long periods when CAISO's generation mix was forecast to contain abundant renewable energy, allow their charging to be automatically optimized to the lowest-carbon hours, and reward them for continued participation with a financial incentive.

Figure 2: count of plug-in and unplug time from residential EVs in California during January 2020 & January 2021 (source: ev.energy) 3

SVCE partnered with ev.energy's data & analytics team to design an events-based managed charging intervention that would deliver three main goals: (i) to reduce the carbon intensity of electricity used to charge SVCE customers' vehicles compared to overnight charging; (ii) to mitigate the duck curve by shifting EV charging demand to daytime hours; and (iii) to ensure that customers were, at minimum, not out of pocket for participating and, at best, realized further energy bill reductions. To achieve the first goal of reducing charging carbon intensity, ev.energy's managed charging algorithm obtained 96-hour and 24-hour generation forecasts from CAISO to predict the lowest-carbon hours in a given week. When the carbon intensity (measured in pounds of CO2 per kWh) of a consecutive 2- hour period falls

below 50% of the average in a given calendar month, EV drivers receive a push notification via the GridShift app alerting them of the "low-carbon event" within the next 12-24 hours and encouraging them to plug in their vehicle beforehand, as shown in Figure 3 below.


Solution design & deployment

Figure 3: example of a low-carbon event received by an SVCE customer in the GridShift mobile app (source: ev.energy)

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To achieve the second goal of shifting EV charging to lower-carbon daytime hours where possible, ev.energy's algorithm calculated an optimal charging schedule for participants based on a number of factors, including the vehicle's battery level at plug-in, the customer's desired battery level, the number of hours between plug-in and the customer's desired ready-by time, the structure of the customer's TOU rate, and CAISO's 24-hour forecast generation mix. With the primary goals of always ensuring the vehicle is charged by the time the customer needed it, and that charging was always done during off-peak hours to ensure continued customer savings, ev.energy's APIs connect to the customer's vehicle to actively switch charging on during the lowest-carbon hours, and off again once the desired battery level is reached. To achieve the third goal of ensuring continued cost savings for customers, low-carbon events were only called during off-peak hours on a customer's rate plan. Given the number and complexity of time-of-use rates across the SVCE territory, this meant that only a subset of customers were alerted to and eligible for certain low-carbon events. To further incentivize customers to respond to low-carbon events, SVCE and ev.energy designed a gamification system whereby customers who plugged in prior to a low-carbon event were automatically charged and awarded with one "reward point." These points could then be redeemed for an energy bill credit at a rate of eight points per $20 credit. SVCE deployed this solution to ~100 EV drivers via the GridShift app between March and April 2021 to test the communication method, dynamic re-dispatching algorithm, and customer participation at the above incentive levels.

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Over the course of March and April 2021, ev.energy's algorithm forecast a total of 17 low-carbon events, defined as periods of 2+ consecutive hours when the average carbon intensity of CAISO's generation mix fell below the average for a given calendar month. GridShift participants were alerted via push notifications on their mobile phones, which were targeted according to their time-of-use rate in line with the goal of ensuring that customers were encouraged to charge only during the off-peak hours of their rate plan so as not to result in higher energy bill costs. Participants' rate plans included EV-A, EV-B, EV2-A, TOU-B, TOU-C, TOU-D, and E-6. If, for example, a low-carbon event were forecast between 12 p.m. and 2 p.m. on a Monday, EV-A participants would not receive a notification and would be excluded from this event because those

hours are defined as part-peak on the EV-A rate plan. Overall, 70% of GridShift participants plugged in before at least one low-carbon event, and 30% plugged in before eight or more low-carbon events (required to earn the $20 bill credit). The low-carbon events occurred over 10 weekends and seven weekdays; weekend participation tended to be 10-15% higher than weekdays, presumably due to a number of factors including greater availability of off-peak hours across all TOU rate plans, greater customer flexibility to plug in, and higher customer engagement with non-work matters. Saturdays saw the highest participation levels, with as many as 50% of GridShift participants plugging in during a low-carbon event. On one weekend, back-to-back events were called on both Saturday and Sunday; while the Saturday event saw


Results & impact

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a 40% increase in customers plugging in during the low-carbon event hours (vs. the average for the same hours in the four prior Saturdays), the Sunday event saw a 30% decrease in customer plug-ins, presumably due to strong participation the day prior. Given overall high participation levels, GridShift was able to shift a significant amount of EV load to low-carbon hours. On average, 110 kWh of EV load was shifted from overnight hours to daytime hours during a low-carbon event, and on a given day when a low-carbon event was called, 42% of the total EV charging load within the day's 24-hour window occurred during the lowest-carbon hours. Figure 4 illustrates the load-shifting and carbon-reduction potential of a low-carbon event, which took place on April 3, 2021. In this graph, an SVCE customer on the EV2-A rate required approximately 35 kWh of charge and had plugged in to charge the evening prior to a low-carbon event. The SVCE customer received a push notification alerting them about a low-carbon event from 10:30 a.m. to 2:30 p.m. the following day, and following customer opt-in (by accepting a later "ready-by" time for the charging session), ev.energy dynamically re-dispatched the customer's charging schedule from 12 a.m. - 4 a.m. (the beginning of the off-peak period on EV2-A) to

instead begin at the start of the low-carbon event during daytime hours. The charging session took place during hours with a carbon intensity that was, on average, 72% lower than the overnight charging period, but still took place during off-peak hours with charging complete before the customer required. The CO2-avoiding potential of low-carbon events is significant, particularly in the spring months when California's generation mix is characterized by higher hydro and solar generation with reduced electricity demand due to the milder weather. Over the course of March and April 2021, for example, the hours classified as "low-carbon events" were 50-70% lower in carbon intensity (measured in lbs CO2 per kWh) than the hourly average for the same period (March-April 2021). Moreover, "low-carbon events" contained hours with a carbon intensity of electricity that were 60-85% lower than the equivalent overnight hours within the same 24-hour period. The impact of SVCE's low-carbon event trial over March-April 2021 was approximately 4,000 lbs of CO2 avoided by participating customers allowing ev.energy to shift their charging schedules from overnight periods to lower-carbon daytime hours. Extrapolated over the course of a calendar year, this would total over 25,000 lbs of CO2 avoided, or the equivalent carbon absorption of over 500 mature trees.

Figure 4: An SVCE customer's EV charging load profile during a low-carbon event on April 3, 2021. Energy consumption is shown on the left-hand axis, with unmanaged EV charging load in grey had the customer not participated in the low-carbon event, and carbon-optimized EV charging shown in green following the customer's opt in to the low-carbon event. Average carbon intensity of electricity given CAISO's reported generation mix for the 24-hour period is shown on the right-hand axis. 7

SVCE's trial of low-carbon events has several implications for utilities and CCAs seeking to use both behavioral nudges and managed EV charging to shift residential EV loads to optimal periods. First, the "new normal" of many residential customers working from home has resulted in increased EV charging flexibility due to longer plug-in durations, presenting the opportunity for load-serving entities to optimize EV charging schedules within a longer window than existed before 2020. Second, a majority of EV drivers will respond to behavioral nudges and incentives to shift their charging schedules, particularly when the load-shifting is done automatically for them. The combination of push notifications sent 12-24 hours in advance of a grid event of any kind (not just low-carbon), a gamified points-based system of participation, and a meaningful incentive (in this case $10 bill credit per

month) have proven effective at shifting the behavior of up to 70% of residential EV customers. Finally, while California's duck curve will require a range of both supply-side and demand-side solutions to ensure that utility-scale solar generation is efficiently utilized, solutions can be deployed today within current system constraints, including residential rate structures that largely incentivize overnight energy consumption. As a next step, SVCE will expand and re-purpose the key elements of low-carbon events (i.e. push notifications, financial incentives, dynamic load re-dispatching) to test grid resiliency events over the summer months (June - October), including CAISO-triggered grid reliability events. SVCE plans to continue to learn from these events-based approaches to EV charging as it plans to re-introduce low-carbon events during the spring months of 2022.


Implications & next steps

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About Silicon Valley Clean EnergySilicon Valley Clean Energy is a not-for-profit, community-owned agency providing clean electricity from renewable and carbon-free sources to more than 270,000 residential and commercial customers in 13 Santa Clara County jurisdictions. As a public agency, net revenues are returned to the community to keep rates competitive and promote clean energy programs. Silicon Valley Clean Energy is advancing innovative solutions to fight climate change by decarbonizing the grid, transportation, and buildings. Learn more at https://SVCleanEnergy.org.

About ev.energyev.energy is a Certified B Corporation® with a mission to make EV charging greener, cheaper, and more accessible to everyone. Its end-to-end software platform connects to a range of electric vehicles and L2 chargers and intelligently manages EV charging in line with utility and network signals, while keeping customers engaged and rewarded through an award-winning mobile app. With a global base of utility customers including SVCE, American Electric Power, E.ON Energy and UK Power Networks, ev.energy manages hundreds of megawatts of EV load on its platform each day. Learn more at https://ev.energy 9

an events-based approach to low-carbon ev charging

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