For years, we’ve heard the warnings that plug-in electric vehicles could overload power grids, disrupt utility business models, and leave their owners stranded at the side of the road with no charging station in sight.
But what's the real-world experience of utilities at the forefront of the EV revolution?
A white paper released Tuesday by Southern California Edison helps shed some light on this question -- and for EV supporters, it’s pretty good news. The massive Southern California utility found relatively minor impacts from the roughly 12,000 plug-ins now within its service territory, both in terms of grid stability and infrastructure costs for itself, and for the driving habits and “range anxieties” of the customers who own them.
That doesn’t mean that the plug-in EV experience has been trouble-free for SCE. For example, it has taken years for it to work out a more smooth-running process with the 180 cities within its service territory for permitting and installing charging systems in PHEV owners’ homes. And multi-family housing remains a challenge, with lots of apartment and condo dwellers interested in buying plug-ins, but very few property owners wanting to pay for the public charging infrastructure to support them.
Even so, there’s plenty in the report to give the utility some confidence in managing the projected 350,000 plug-in vehicles it expects to be in its service territory by 2020. “None of us are sitting there saying, 'The sky is falling,'” is how Ed Kjaer, SCE’s director of plug-in electric vehicle readiness, put it in an interview this week.
“The grid is constantly evolving; there’s billions of dollars of investment being made into the grid in California today,” Kjaer said. And while all that investment is “not being made specifically for electric transportation’s benefit, electric transportation is benefiting,” he said.
Here are some of the report’s key findings.
1) Plug-in EVs make up a tiny fraction of the utility’s grid infrastructure upgrade needs. It’s been a truism in the utility industry for some time that plug-in vehicles, which can represent a power draw equal to one-quarter to nearly the equivalent of a full household load, will be a major strain on local distribution grids. But SCE’s report found that, of the 400 or so grid circuit improvements made in neighborhoods where plug-ins are located since 2010, only 1 percent were made specifically to address those EV loads themselves.
That’s because today’s relatively small number of plug-in EVs, even when concentrated in certain neighborhoods, still fit well within the utility’s plans for upgrading the grid in general, the report found. “Just as we now size our transformers to serve plasma TVs, we integrated the expected load from PEVs into standards applicable to our 'grid modernization' efforts,” is how the report put it.
2) Certain key charging management methods can mitigate the impacts of plug-in charging on a mass scale. Despite the findings of almost no grid infrastructure costs associated with EVs at present, the proliferation of thousands of grid-connected cars can still cause stability problems, Kjaer noted. But with a few tweaks to the way those cars are programmed to charge, many of those problems can be avoided, he said.
Such is the case with so-called “end charge” time programming. Everyone knows that cars should be charged overnight, when off-peak power is cheap and available. But just how should that nighttime charging routine be scheduled? It turns out that setting a “start charge” time for lots and lots of plug-in EVs is a problem, because the resulting spike in power use at that moment could disrupt grid stability and power pricing.
But setting the cars to all end their charging at the same time -- usually in the morning, before their owners drive them to work -- neatly solves that problem, he said. That’s because, when they’re plugged in for the night, some only need to be filled up a little, while others need to be recharged almost completely. Since each car knows just how long it takes to top off its battery, each will start at a much more randomized time, and yield a far less “spiky,” charging profile overall.
3) Plug-in owners are driving and charging their cars in predictable and manageable ways. SCE has been a bit lucky in the pattern of plug-in ownership in its service territory. First of all, while about half of the EVs in its territory are being charged with more powerful 240-volt Level 2 chargers, the rest are still being charged with Level 1 chargers, which use 120-volt household current, making for a much less hefty power draw.
Even for those customers who do have Level 2 charging available, less than half report they’re using it on a regular basis, the report found. Fast-charging systems, which use high-voltage direct current to replenish EV batteries in as little as half an hour, require a lot more power, but so far they’re quite rare, and will be concentrated in public locations where they can be planned and accounted for, Kjaer noted.
4) Multi-family housing is a challenge for plug-in vehicles. If almost every plug-in EV out there today is being charged at the home garage, what do you do about people who don’t own their own garages? According to SCE’s research, fewer than 5 percent of owners of multi-family properties such as apartment and condos are even considering installing EV charging infrastructure that could be used by residents in common. That’s a lot lower than the number of multi-family dwellers who say they’re interested in buying a plug-in.
5) Tracking just how many plug-in cars are out there can raise tricky privacy concerns. Kjaer also raised an interesting side note, not covered in the report: of all the EV owners SCE estimates live within its service territory, only about 40 percent have actually reported that fact to their utility. That means that the majority of plug-ins out there are being charged at home without the utility knowing about them. That could grow to be a significant issue, if the overall number of plug-ins keeps growing as quickly as SCE estimates.
Luckily for it and other California utilities, a state law passed in 2012 provides for the Department of Motor Vehicles (DMV) to let utilities know when and where new plug-in cars have been registered for ownership, which gives each utility a better understanding of where those cars will be getting charged, Kjaer said.
The same law also restricts the utilities to using that information only for grid-planning purposes, while barring them from using any personal data, he added. In other words, utilities can’t even share that information with its customer service or billing departments, let alone call up those EV owners to ask them to sign up for special plug-in charging rate plans or other such offers.