EPA Rolls Out First Draft of EV Charger Efficiency Specification

Mon, 03/14/2016 - 16:23 -- MrGreen

The U.S. Environmental Protection Agency (EPA) is moving ahead with the first program that drives towards improving energy efficiency in Level 1 and Level 2 Electric Vehicle Service Equipment (EVSE)1. As discussed in a 2015 Mr. Green blog, the EPA has identified a non-charging-state energy savings opportunity of up to 265 kWh per charger over 5 years since a majority of home chargers are in standby mode most of the day.

The first draft specification identifies distinct EVSE functions:

  • Primary - An EVSE’s primary function is to provide current to the connected load (i.e. charge the EV)
  • Secondary - These functions enable, enhance, or supplement a primary function. This includes illumination of a display or indicator lamp, automatic brightness control determining the brightness of a display or lamp, full network capability, occupancy sensing when a human or object is present, wake-up function, public access control, and control pilot signal.
  • Tertiary - Any other function (i.e. EMC filter, area lighting)

EVSE modes of operation include:

  • Off mode - Equipment is connected to external power and is only providing tertiary functions. Intended to be the lowest EVSE power mode and can only be addressed with a manual switch.
  • On mode - Equipment is connected to external power and provides at least one primary function.
  • Idle mode - Equipment is connected to external power and can promptly provide a primary function but isn’t doing so.
  • Partial-on mode - Equipment provides at least one secondary function but no primary one.

Draft 1 introduces requirements that address efficiency in partial-on and idle modes.

Measured partial-on mode power (PPartial_ON) must be ≤ the maximum partial-on mode power requirement (PPARTIAL_ON_MAX) as calculated below:

Where: PPARTIAL_ON_MAX = maximum partial-on mode power requirement, PPARTIAL_ON_BASE = base partial-on mode power allowance for all products (see table below), PWAKE_i = partial-on mode power allowance for each active, in-use networking/control protocol giving remote hosts the capability to wake a product from partial-on mode, for a total of n allowances.

Product Function Partial-On Mode Power Allowance (W)
Base Allowance for All Products
(PPARTIAL_ON_BASE)
2.2
In-use Wi-Fi or Gigabit Ethernet Protocols
with Wake Capability (PWAKE_i)
1.0
In-use Cellular with Wake Capability (PWAKE_i) 1.0
Other In-use LAN (Local Area Network)
Protocol with Wake Capability (PWAKE_i)
1.0
In-use Occupancy Sensor (PWAKE_i) 0.3

Source: ENERGY STAR EVSE Product Specification; Draft 1, Version 1

Measured idle state power (PIDLE) must be ≤ the maximum idle state power requirement (PIDLE_MAX) as calculated below:

Where: PIDLE_MAX = maximum idle state power requirement (W), max current is the nameplate maximum current (A), and PIDLE_BASE = base idle mode power allowance for all products, (see table below), PIDLE_i = idle state power allowance for each applicable product function listed below, for a total of n allowances.

Product Function Idle State Power Allowance (W)
Base (PIDLE_BASE) 2.2
In-use Wi-Fi or Gigabit Ethernet Protocols with Wake Capability (PIDLE_i) 1.0
In-use Cellular with Wake Capability (PIDLE_i) 1.0
In-use LAN (Local Area Network) Protocol with Wake Capability (PIDLE_i) 1.0
In-use Display (PIDLE_i) PON_MAX = (4.0 × 10-5 × ℓ × A) + 119
× tanh (0.0008 × (A – 200.0) +
0.11) + 6.0
Where: A = screen area (in2), ℓ = maximum measured display luminance (candelas per m2), and tanh is the hyperbolic tangent function

Source: ENERGY STAR EVSE Product Specification; Draft 1, Version 1

In addition to the above requirements, an EVSE must incorporate Auto Power Down (APD) functionality, enabled by default. Products may offer users the option (via system menu or physical switch) to modify APD timing in 10 minute intervals, or to disable APD entirely. APD timing default settings can be:

  • ≤ 30 minutes - Acceptable as a compliant default setting. If APD is set by default to ≤ 30 minutes and can’t be disabled or increased to over 30 minutes, EVSE idle state power requirements don’t have to be met.
  • 30 minutes < APD Timing ≤ 2 hours - Acceptable as a compliant default setting. If APD can be disabled or timing can be set to > 30 minutes, EVSE idle state power requirements must be met.
  • > 2 hours 30 minutes, EVSE idle state power requirements must be met.

The EPA will be hosting a webinar on March 16th to discuss the specification and test method drafts. To register, click here. To be added to the distribution list for updates, send your contact information to ElectricVehicleSupplyEquipment@energystar.gov. For more information, visit the ENERGY STAR Electric Vehicle Supply Equipment webpage.

  1. Level 1: a galvanically-connected EVSE with a single-phase input voltage nominally 120 volts AC and maximum output current ≤16 amps AC. Level 2: a galvanically-connected EVSE with a single-phase input voltage from 208 to 240 VAC and maximum output current < 80 amps AC