Non-charging-state energy savings opportunity could be as high as 265kWh per charger over five years since a majority of home chargers are in standby mode most of the day.
The U.S. Environmental Protection Agency (EPA) has released the first draft programme specification geared to boost the energy efficiency in Level 1 and Level 2 Electric Vehicle Service Equipment (EVSE)1. According to the agency, the non-charging-state energy savings opportunity could go up to 265kWh per charger over five years since for the most part of the day, home chargers are in standby mode.
Three distinct EVSE functions are identified in the draft spec—Primary: An EVSE’s primary function is providing current to the connected load (i.e. charging the EV); Secondary: These functions enable, enhance or supplement a primary function, including 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; and Tertiary: All other functions (i.e. EMC filter, area lighting).
EVSE modes of operation include: 1) 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; 2) On mode: Equipment is connected to external power and provides at least one primary function; 3) Idle mode: Equipment is connected to external power and can promptly provide a primary function but isn’t doing so; and 4) Partial-on mode: Equipment provides at least one secondary function but no primary one. Only requirements that address efficiency in partial-on and idle modes are included in the draft.
Measured partial-on mode power (__P__Partial_ON) must be ≤ the maximum partial-on mode power requirement (__P__Partial_ON_MAX) as calculated below:
Where: __P__Partial_ON_MAX = maximum partial-on mode power requirement, __P__Partial_ON_BASE = base partial-on mode power allowance for all products #P###WAKE_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.
Figure 3: Source: ENERGY STAR EVSE Product Specification; Draft 1, Version 1
Measured idle state power (__P__IDLE) must be ≤ the maximum idle state power requirement (__P__IDLE_MAX) as calculated below:
Where: __P__IDLE_MAX = maximum idle state power requirement (W), max current is the nameplate maximum current (A), and __P__IDLE_BASE = base idle mode power allowance for all products, __P__IDLE_i = idle state power allowance for each applicable product function listed below, for a total of n allowances.
Figure 5: 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: 1) ≤ 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; 2) 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; and 3) > two hours: May only be enabled by end user and not acceptable as a compliant default setting. If APD can be disabled or if APD timing can be set to > 30 minutes, EVSE idle state power requirements must be met.