Some funny math for EV-Charging infrastructure

One of the challenges with EV-Charging is that we would need to provide more charging infrastructure in the busiest locations, e.g. in the office parking lot, so cars could charge while people are at work. However, we know from experience that battery chargers inject a lot of harmonic noise in power circuits.

The following is a stylized example, which assumes that one or more EV chargers are provided on premises in a major building which has a basic harmonic noise load of 20%, this is not uncommon. One example of a building where this level of harmonic noise was found was Caribe Resort, in Orange Beach, AL; harmonic filters saved almost 19% in this case. The following numbers are stylized for the ease of the calculation, but provide an illustration of how this works out:

  • We assume our building has a consumption of 300,000 kWh/mo, with 20% THD.
  • EV-charging increases the load by 30,000 kWh/mo (10%). We know from experience that battery chargers produce a high level of harmonic noise. So let’s assume the harmonics increase by 5% and the total load is now 25%, in short, the power bill goes up by not just 30,000, but by 30,000 plus 25% of 330,000 or 16,500, for a total of 46,500 kWh/mo. I.e, the incremental deterioration of the power quality would drive up the losses in the facility.
  • If instead harmonic filters are deployed simultaneously, they would be 90% effective and reduce the new total of 346,500 kWh by .90 x 25% or 22.5%, ergo, the savings would be or 77,963 kWh/mo, and the new load of the facility would be 268,538 kWh/mo.
  • In short, by making this one project, the net result is a decrease in electrical bills by adding the EV-charging and simultaneously installing harmonic filters.