Cellular vs Wi-Fi: Which is best for smart EV charging?

Gone are the days where EV chargers were merely dumb devices that only served the simple task of “plug-in and charge”. If you run an EV charging business, then you already know all too well the importance of networked charging infrastructure for load management, billing, maintenance, EV driver services and so much more.

The communication interfaces from EV chargers to the charging management backend often revolve around three options: cellular, Wi-Fi, and Ethernet / LAN. Ethernet provides highly stable and secure data communications. Yet, all too often, the cost and complexity of running, tracing, and fire-proofing cables limit its applicability. Either the Ethernet connection is easily accessible where the chargers are (which in most cases, it isn’t), or the deployment takes place in new buildings where Ethernet connections are taken into consideration during construction.

Between cellular and Wi-Fi, it might not always be straightforward which is the better option for your charging solution, given the different charging use cases – private, semi-public, and public. To help you with your decision, in this blog, we will take a deep dive into how these two technologies compare in terms of:

1. Communication reliability
2. Security
3. Remote access
4. Charger positioning

1. Communication reliability

Uninterrupted data communication is fundamental in smart charging. In public and semi-public scenarios, real-time transmission of user command and authorization data is a must-have to initiate charging sessions and handle billing. Likewise, accurate and up-to-date information on charger availability enables value-add digital services like queuing prediction and smart navigation. In home contexts, reliably connected chargers enable dynamic, intelligent management of charging schedules to reduce energy costs and carbon intensity on the grid.

Wi-Fi is readily available on most, if not all residential and commercial premises. But depending on the customer’s WLAN infrastructure also means you have little control over the connection quality. Besides unexpected network outages, Wi-Fi is prone to interference issues as multiple devices vie for bandwidth usage in the unlicensed frequency bands (2.4 GHz and 5 GHz). In addition, Wi-Fi’s short range often poses coverage problems and requires the installation of repeaters.

Already deployed all over the world, cellular networks using the licensed spectrum are ubiquitous and highly reliable. While some might be concerned about the mobile coverage in indoor and underground garages or on remote roadways, IoT-focused cellular solutions address this challenge using a multi-network SIM card and multiple redundant data routes. Newer cellular technologies like LTE-M and NB-IoT are also better optimized for range and coverage at difficult locations.

2. Security

Security threats for EV charging are real, and they pertain to not only an extensive network of public chargers but even on the small scale of private and home charging. There exists a wide range of potential attacks - from electricity theft, cable theft, and Denial-of-Service to network infiltration for ransomware and nefarious grid disruption.

Connecting your EV chargers to end users’ Wi-Fi networks opens two-way security risks for both you and your customers. An EV charger can be used as a backdoor to the users’ home or workplace network to steal their Wi-Fi credentials and eventually access private and sensitive information.

Vice versa, your chargers could be hackers' targets with the perilous intention to manipulate the maximum charging current and destabilize the local electrical system. When enough chargers are affected, the larger energy grid can be at stake. Security threats of public Wi-Fi networks are nothing new. But even with private Wi-Fi, proper measures to protect the local network and its connected devices are often neglected. Using default Wi-Fi passwords, failing to update device firmware/software, or leaving recent bugs unattended are just a few examples.

With cellular connectivity, you can separate the EV charging network from the customer’s local Internet infrastructure, eliminating unnecessary attack points. Versatile cellular IoT solutions further provide a virtual private network where all data is encrypted and two-way communications with EV chargers are highly secured – a critical requirement that is missing in previous versions of OCPP (OCPP 1.6 backwards) and other charging communication protocols.

3. Remote access

For charge point operators and manufacturers, being able to access and log into remote chargers makes troubleshooting and customer support a lot faster and more cost-effective. Instead of having to travel to the site, your technicians can get charger logs for diagnostics, reboot the charger, and modify its settings easily from afar – saving time and costs and reducing issue resolution time. Remote access also helps you streamline your commissioning process by enabling remote configuration of new chargers, for example, their OCPP parameters.

When it comes to Wi-Fi-connected charge points, creating remote sessions requires the public IP address of the local network to be static or dynamically traceable. This comes with multiple problems. On one hand, it involves a reconfiguration of the Wi-Fi router and firewall rules as well as access to administrator passwords – which demands network engineers and users’ consent. On the other hand, making customers’ IoT routers visible to external traffic can expose their networks to more security vulnerabilities.

Equipping your chargers with IoT SIM cards that use static private IP addresses helps you bypass these issues. Fixed private IP addresses simplify remote access as they remove the need to install extra applications like dynamic DNS and port forwarding on the device to trace the constantly changing IP. On top of that, a virtual private network enhances security by ensuring your chargers are not reachable from external points.

4. Charger positioning

For public charging stations or those that are deployed on private and commercial premises but open to public use, charger positioning is vital for EV roaming and optimal service delivery. EV roaming allows drivers to use chargers managed by multiple charge point owners and operators even if they are only a customer of one e-mobility service provider. Drivers can locate, book and access all charging stations within the roaming network – conveniently from a single mobile app.

Cellular modules often come with integrated GNSS and GPS capabilities or at least cell-level positioning, allowing you to immediately locate the chargers the moment they are installed and go online. With Wi-Fi, this is most likely not an option.

Conclusion

Many often see Wi-Fi as the inherent choice for home and private charging while cellular connectivity is more relevant for public chargers. However, this is not always the case. Wi-Fi is attractive because you can bypass connectivity costs, but it also limits your control over product/service reliability while incurring more security risks and operational costs – be it residential, workplace, or commercial charging use cases.

What’s more, with the emergence of new cellular IoT providers, connectivity costs have decreased over recent years, and there are also more flexible data plans that are tailored to the consumption needs of EV chargers. At the end of the day, it all depends on how you weigh your business and technical requirements.

About emnify

From reliable connectivity and a one-stop portal for complete network visibility and control to powerful APIs, automated cloud integration and advanced security features, emnify provides you with all the tools you need to deploy and operate your EV chargers anywhere and at any scale. Learn more about how we can help your EV charging business here or contact our cellular IoT expert to book a demo and free consultation today.