Back to News

Why is Bi-Directional Charger Operation So Important for EV Fleets?

(Joseph Gottlieb, CTO, Thursday, January 30, 2020)

One of the often-cited positives of electric vehicles (EVs) for fleet operators is their reduced operational expense (OpEx) relative to fossil fuel powered vehicles. Obviously, one of the key components in the EV fleet OpEx equation is the cost of electricity. A few decades ago, electric utilities started using “time of day” (also known as “metered”) pricing , where the price of power varied based on the demand. When metered pricing began, the peak rate period tended to be during the daytime (9am-5pm). As solar photovoltaic (PV) power became more commonplace, peak hours have shifted in many metropolitan areas from daytime to the period of 5pm to 9pm – when PV is no longer producing energy. This is an issue for operators of EV fleets, since most of their vehicles come off of duty and need to be charged during this time.

Bi-directional charging infrastructure significantly changes this equation. Most fleet vehicles do not return to their charging location “empty” – they still have energy in their batteries. Bi-directional chargers allow this energy to be returned to the utility grid (also known as vehicle-to-grid, or V2G). Most utilities that have implemented metered charging have also implemented the concept of “net metering”, which means that power that they put back on the grid reduces their bill, and does so at the rates in place when they put the power back on the grid. This means that the energy still in the vehicle batteries could be returned to the grid during peak hours, and the vehicles can be recharged at a lower rate after peak hours end (for instance, during 9am to 6am). This can significantly reduce the utility charges that are one of the critical components of EV fleet OpEX.

Rhombus Energy Solutions is an expert in the development and manufacturing of high-power bi-directional DC charging systems, with a power range from 60kW to 500kW. We apply our expertise to build chargers that thrive in continuous operation scenarios – we have shipped hundreds of high-power chargers with vehicle-to-grid capabilities to a variety of customers. Rhombus chargers are also designed from the ground up to be integrated with energy storage solutions and renewable power sources such as PV panels to minimize grid demand. Our VectorStat® software provides intelligent demand management capabilities, including peak shaving, to reduce energy costs. Rhombus looks forward to playing our part in the electrification of the transport infrastructure. Find out how we can help you by contacting us at

Back to News