Building a retail EV charging site is a great opportunity for retailers to boost revenue potential from their existing customer base by providing EV charging as an additional service. To ensure the success of retail EV charging, there are a few key decisions that need to be made, and choosing your charging power wisely is at the top of this list.
This blog post provides forward-thinking retailers with a guide to making informed decisions about the amount of EV charging plugs and power they should offer at their sites to optimize customers’ shopping experience and maximize return on investment.
Why is power important in EV charging?
Before delving into the selection and deployment stage of EV charging stations, it’s essential to understand what we mean when we talk about the power rating of an EV charger, and how power influences key metrics like charging times.
Power, measured in kilowatts (kW), determines the speed at which a car charges. Every charger is given a power rating to indicate how much power it can deliver. This is different to energy, measured in kilowatt-hours (kWh), which is used to describe EVs batteries or capacity and determines the vehicle’s range.
Figure 1 shows how power and energy (kW and kWh) are linked, as, in general, the higher the power of a charger, the faster a car battery charges. More power delivered by a charger means more range added in a shorter period of time.
So do more powerful charges = faster charging times = happier customers? Not exactly. Contrary to common belief, power isn’t constant throughout the charging process. As a battery fills up, charging speed decreases due to the charging curve. This means that advertised charging speeds may only be achievable with nearly empty batteries.
As Figure 2 illustrates, in practical terms, unless drivers arrive with nearly depleted batteries, they won’t receive the maximum power as advertised by the car manufacturer, but rather a reduced amount.
Since accessing higher power also incurs significant costs, it’s prudent to base your charging hub design on average charging power (speed) rather than maximum power. In the absolute worst-case scenario, this might slightly prolong the overall charging session by a few minutes. However, the savings gained from opting for lower available power far outweigh any inconvenience.
Choosing the right power for your scenario is therefore a more complex issue than it first seems. Finding the optimal balance between meeting customer needs and maximizing your profit requires an understanding of your customer to help you find the sweet-spot for the amount of chargers and power at your site.
How to choose the right power for your EV charging site needs
When designing an EV charging site for your retail customer, the most important thing to consider is average customer dwell time. The expected dwell time of EV drivers using your chargers will align with typical customer visit durations. It is crucial to know your average customer’s dwell time, because customers prefer not to be inconvenienced when shopping by having to relocate their vehicle once it’s fully charged. They also want to receive the power they need without having to wait longer than planned.
It’s also important to understand whether EV charging will be a primary activity or a secondary convenience at your site. Most retailers fall into the latter category, where EV charging complements the primary activity of shopping. EV drivers never want to wait to charge, but their tolerance is even lower at retail sites if the driver is charging opportunistically. If an EV driver sees a full charging bay when shopping at a retail site, instead of waiting they are likely to charge at another time, or even shop at a different retail site with better charging availability. Therefore it’s essential to offer enough plugs and make waiting times rare.
Power also needs to be adjusted to a secondary charging scenario. If power is too low, charging at the site for a short time during a shopping session is not worth it for EV drivers. On the other hand, if the power offered is too high, meaning the EV is fully charged before the customer finishes their shopping session, the customer’s charging session will end earlier than expected. In addition to the inconvenience this causes EV drivers, it negatively affects ROI for CPOs as it leads to charging spaces being occupied by inactive charging sessions.
To determine the optimal power per plug to provide customers at a site, operators should calculate the average customer dwell time. Kempower can help retailers carry out the calculations to determine this level.
For example, if a customer with a 40 kWh EV battery arrives with a 30% charge and plans to charge during a typical 25-minute shopping trip, and assuming a good ending state of charge of at least 70%, the minimum power offered by a charger should be approximately 38kW. Of course, retailers don’t need to provide exactly 38kW, but it should be in the range: A charging time that is too long or too short will dampen customer experience, so it’s important to match charging time to dwell time accurately.
What if your average customer dwell times vary? While there will be an overall average, there will always be anomalies among your customers. To cater to a range of customers with varying charging needs, it’s wise to seek flexible solutions capable of redistributing available power between plugs as required, all while avoiding the need for excessive installation sizes.
How to meet customer needs with optimized EV charging infrastructure
Ensuring customer satisfaction and maximizing revenue involves more than just choosing the right power. Other ways you can make the most of the power you offer include:
- Increasing plug availability: EV drivers have little patience for waiting, especially during secondary charging activities like shopping. Offering more charging plugs is a good alternative to providing more power across multiple plugs, reducing wait times and preventing potential revenue loss.
- Offering dynamic power sharing: Distributing available power across charging points based on the charging curve of each EV model prevents overloading individual stations and ensures optimal charging speeds for all customers.
Using modular charging solutions: Investing in scalable charging solutions will help you to adapt to evolving customer behaviors and increasing battery capacities as your retail charging business grows.
Implementing a retail EV charging site
Once you have done your customer research and know how much power to offer, the final step is to determine the availability of power at your site. The power offered by the grid at your site can significantly impact site design and how quickly a charging hub can start operation.
To assess the available power on their site retailers should:
- Determine the site’s power capacity during peak operational hours.
- Evaluate the site’s power availability during off-peak hours or when the main activity is less busy.
If there is sufficient available power (i.e. enough to deliver the optimal power calculated using your research into customer behavior) your priority should be matching this capacity. When determining whether power is sufficient, remember that a flexible and dynamic solution can assist in maintaining power commitments across multiple plugs, utilizing less input power by efficiently adjusting to charging curves and redistributing power between plugs as necessary.
However, if there isn’t sufficient power available, retailers should begin contemplating ways to expand their power capacity through a new point of connection and may consider constructing a separate EV charging hub or introducing energy storage to make up for insufficient levels of grid power during times of peak demand.
The Kempower team can advise you on the optimal numbers of plugs and level of power you should be offering at your site. Get in touch to discuss your options.
