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Will My EV Crash the Grid?

Written by: Pete Westlake
ecoPreserve is pleased to bring you this guest article from Pete Westlake, Manager of New Products and Services at the Orlando Utilities Commission (OUC). OUC is Florida’s second-largest municipal utility, providing services to Orlando and parts of Orange County for almost a century.

As we ponder the transition to Battery Electric Vehicles (BEVs), pressing questions arise:

Will the widespread adoption of BEVs strain our power grid beyond capacity? Could plugging in my BEV be the tipping point for our beloved electric grid, upon which we rely for countless daily activities?

While personal BEV owners voice those concerns, they loom even larger for commercial fleet operators. Let’s explore this issue in greater detail.


First, let’s examine a few energy concepts as they apply to BEV charging. Utilities can flex up and down to meet customer demand. However, we must maintain the capability to always serve our peak demand plus 15% to 20% reserve. Demand fluctuates based on consumer needs, with peak power demand usually occurring between 4 p.m. and 7 p.m. in the summer—when people return home, use appliances, and charge their cars. As night falls, electricity usage decreases.

When our demand peak is lower, we can use the excess capacity to serve higher loads for our customer base, sell that capacity on the open market, or reduce our electricity generation.

The graph at right shows the demand peak for July 5, 2017, before many EVs were added to the grid. As you can see, we can generate more than we need throughout the day. We have assessed vehicle registration data in Orange County, Florida, revealing 1.2M registered vehicles. This represents a total demand of 15,600 MWh/day. OUC’s current daily capacity is 39,840 MWh/day, and our current load is 19,785 MWh/day. If we can control when this demand happens during the day, we will have more than enough capacity for EV charging in the foreseeable future.


How much energy does the average BEV consume? Typically, an individual drives around 13,000 miles annually[1], averaging roughly 35 miles per day. Although this figure may double or triple for certain commercial applications, let’s stick to a conservative average of 40 miles daily. With typical vehicle efficiency at around three miles per kWh[2], this equates to an average requirement of about 13 kWh per day per vehicle.


The fuse box can be rated anywhere from 100 to 400 amps in a typical home. For this example, we will use a standard 200-amp panel. This panel can handle up to 48 kW of demand at any time. The average household typically uses two to 20 kW/hour depending on what appliances are active during that hour.

Over the full day, a home will use between 30 and 100 kWh. Panel capacity could theoretically reach up to 1,000 kWh/day (assuming full load throughout the day; this is not the case for a typical home). So, while adding four BEVs (52 kWh/day) might double a home’s daily usage, it shouldn’t cause significant issues. However, simultaneously charging all vehicles at peak demand could overload the panel with dire results. For example, plugging in four BEVs may add as much as 36 kW, leaving 14 kW for the home. If this were to occur at a peak time, this could cause the fuse panel to overload.

The grid is designed to accommodate such loads for residential usage, provided consumers charge their cars during off-peak hours. Time-of-use (TOU) rates incentivize this behavior. TOU is where prices vary based on the time of day, highest when electricity demand is high and low when it is not. Homeowners, however, should assess their breaker panel’s capacity, especially with multiple electric cars. As highlighted above, charging several vehicles simultaneously without safeguards could overload the panel. We do not feel that residential load due to BEV adoption will adversely affect the grid.


Commercial fleets pose a more intricate challenge. Despite representing only 1% of total vehicles, their mileage can be significant, though unlikely to exceed 10-15% of the total miles driven in the US. According to estimates from the alternative fuel database, out of the 2.8 trillion miles driven, only 3 billion miles are attributed to commercial vehicles. The same applies to commercial settings as we examine local infrastructure for residential needs. We probably won’t have sufficient power available at fleet sites than the fleets outpacing our generation capability. This is why we ask our customers to engage the utility when electric vehicles are starting to be considered, not after they are purchased.

To appropriately analyze commercial fleets, we must consider more than just range. We must also consider factors like mileage, duty cycle, and rapid charging. However, for this analysis, we can assume most vehicles will charge overnight during off-peak hours, aligning with residential load patterns. So, just as residential charging is not likely to adversely impact the grid, so it is for commercial customers. But, just as with residential charging, the biggest potential issue is, “How much power do I have at my disposal?” If it is less than the fleet needs, the utility will take time to provide that additional power. The time needed to address the issue depends on the constraint and whether a transformer, secondary, or substation must be added.

A few fleets will require rapid charging due to the need for quick turnaround vehicles such as emergency response, long-haul trucking, and truck rentals. For rapid charging, we may need to consider onsite battery storage. Battery storage allows us to flatten demand, ensuring a consistent draw from the grid while supplying the charging equipment during peak times. This is an important factor because, for OUC, the peak demand is a fixed charge based on the highest peak demand for any 15-minute interval during the billing period. This makes managing demand peak a critical part of the electrification of transportation.

So, what does all this mean? We have some good news: Long-haul fleet electrification isn’t likely to occur soon, except for specific routes where infrastructure is available. This means that most charging will likely occur “behind the fence,” overnight. Consequently, it’s unlikely to strain the grid, except for concerns about the power capability at specific fleet locations. This issue may be problematic and is likely to take time to resolve. For example, it can take months to replace a transformer and years to provide additional power capacity at the location. There may be some very densely populated areas like Manhattan, where this is even more difficult to address. However, providing power is achievable for the lion’s share of cities, assuming we have the appropriate time to prepare. This highlights the need for fleets considering electrification to engage their utility as soon as possible.


We will have even more good news if we successfully pair solar with EV charging. In OUC territory, solar is growing at 1,500 kW per month and currently has a capacity of 90 MW at peak during the day. Charging predominantly occurs at home or work. Home charging will take up excess capacity overnight, while workplace charging presents an opportunity to leverage excess solar energy produced during the day. The pairing of charging solar during the day and excess capacity overnight makes BEVs a great benefit to the grid, not a risk.


I wish I could say that this is the end of the story. Unfortunately, the electrification of the transportation market isn’t the sole concern. This issue needs to be viewed from a higher level.

We’re experiencing unprecedented growth in the utility industry, including data centers, cryptocurrency mining, and indoor grow farms. The convergence of these new load growth industries will directly impact our ability to supply power. Additionally, our traditional method of power generation, in part, involves burning fossil fuels. Most utilities have 2030 and 2050 net-zero carbon emissions goals, meaning we’re transitioning toward greener energy sources like solar and wind.

The good news is that transportation offers the best pairing between supply and demand. Typical charging occurs overnight when grid demand is lower or can be paired with solar production during the day using workplace charging. This makes transportation an ideal candidate for managing load growth.

In essence, the impact of electric vehicles on the grid depends on our current decisions and processes. Thoughtful charging practices and innovative solutions like storing solar energy in car batteries can alleviate grid strain. Conversely, haphazard growth without load management could necessitate significant grid expansion. To optimize this transition, we must strategically pair electricity production with consumption, which presents a historic opportunity that can potentially drive down rates by maximizing asset utilization.

So, to answer the original question, will my EV take down the grid? The answer is no… presuming we expand this new growth thoughtfully.