Solar Lattice

Function

PV-only backup outlet

ID
func:pv-only-backup
IRI
https://solarlattice.org/kb/func/pv-only-backup
Status
active
Also known as
Secure Power Supply, SPS, Sunlight Backup, opportunity power, Secure power supply operation, SMA Backup Secure, Backup Secure
Category
Energy management
Function kind
energy-management

PV-only backup lets a grid-tied inverter power a dedicated outlet from the PV array during a grid outage. While it does this, the inverter is disconnected from the grid and does not export. The power available follows the irradiation. If there is an overload, an underload or too little sun, the outlet drops out and the inverter retries 20 seconds later, so loads that need a stable supply must not be connected. On the Sunny Boy Smart Energy, SMA Backup Secure needs SMA Backup Start in the inverter. To set it up, set Configuration of the backup type to Emergency Power Mode and set Backup Voltage to 120V. Enphase calls this function Sunlight Backup. These sites must be set to Load with Solar production, and installers need IQ Battery certification to commission them.

<!-- review notes

Claims

subclass_of

c1 drafted · lead Backup power

During a grid outage, loads are supplied from PV alone, without a battery.

requires

c2 drafted · lead SMA Backup Start proposed

Scope: products Sunny Boy Smart Energy US-50

SMA Backup Secure works only when SMA Backup Start is installed in the inverter.

review note: support check: partial - Passage says Backup Secure requires Backup Start, but it does not mention the SBSE-US-50 scope, and it says Backup Secure can use battery or PV.; review: partial - The passage confirms SMA Backup Secure works only if SMA Backup Start is installed, but it says the outlet can draw from the battery or the PV system, so it does not support framing this as a PV-only function.

reconnect_delay

c3 drafted · lead nominal 20 SEC

Scope: products Sunny Boy 3.0-7.7-US-41 proposed

Conditions: Automatic attempt to restore the outlet voltage after a brief interruption caused by overload, underload or insufficient irradiation

c4 drafted · lead nominal 20 SEC

Scope: products Sunny Boy 3.0-7.7-US-40 proposed

Conditions: Automatic attempt to restore the outlet voltage after a brief interruption caused by overload, underload or insufficient irradiation

c6 drafted · lead nominal 30 SEC

Scope: products Solis S6-EH3P(75-150)K10-NV-YD-H-US

Conditions: Recovery after the first overload fault while backing up loads from PV only

c7 verified · fact nominal 3 MIN

Scope: products Solis S6-EH3P(75-150)K10-NV-YD-H-US

Conditions: Recovery after the second overload fault while backing up loads from PV only

verified by: review-workflowverified on: 2026-10-24review note: possible conflict with c8 (same source; check the conditions)

c8 drafted · lead nominal 10 MIN

Scope: products Solis S6-EH3P(75-150)K10-NV-YD-H-US

Conditions: Recovery after the third, fourth and fifth overload faults while backing up loads from PV only; after the sixth fault a hard reset is needed

review note: possible conflict with c7 (same source; check the conditions)

trip_time

c5 verified · fact ≥ 5 SEC

Scope: products Sunny Boy 3.0-7.7-US-40 proposed

Conditions: The 'Short circuit in the SPS power outlet' event is raised when the starting current stays above the permitted load current of the SPS connection for more than this time

verified by: review-workflowverified on: 2026-10-24review note: support check: partial - The passage gives more than 5 s for the overshoot, but it does not state the 'at least' framing or the trip-time classification beyond the event text.

Data