Solar Lattice

Function

Volt-Watt

ID
func:volt-watt
IRI
https://solarlattice.org/kb/func/volt-watt
Status
active
Also known as
voltage-active power mode, P(U), P(V), DVWC
Category
Grid support
Function kind
grid-support

Volt-Watt lowers the active power output of an inverter or battery system as grid voltage rises, following a programmable voltage versus power curve. On the Tesla commercial controls the response is open-loop, based on overvoltage measured at the POI meter. The curve is set with an enable flag, high voltage setpoints V1 and V2, a power limit P2 and a response time constant, and the resulting power limit can be read back over Modbus. Tesla project engineers can program the curve during commissioning, or it can be changed in real time over Modbus or DNP3 points. IEEE 1547-2018 defines a voltage-active power mode that can be switched on or off. Category A DER do not have to provide it, and the default settings guidance leaves it off. Volt-Watt is listed as a feature of the CPS SCA25KTL-DO/US-208 and SCA36KTL, the Solectria PVI series and Generac PWRmicro equipment. On the CPS SCA25KTL it is enabled for IEEE 1547-2018 and Rule 21 and disabled for ISO-NE.

<!-- review notes

Claims

setting_range

c1 verified · fact 240–288 V

Scope: products Solis RHI-1P(5-10)K-HVES-5G-US; standard CA Rule 21 proposed

Conditions: Volt-Watt V2 (Vstart), Rule 21 settings, 240 V rated grid

verified by: review-workflowverified on: 2026-10-24

c3 verified · fact 240–288 V

Scope: products Solis RHI-1P(5-10)K-HVES-5G-US; standard CA Rule 21 proposed

Conditions: Volt-Watt V3 (Vstop), Rule 21 settings, 240 V rated grid

verified by: review-workflowverified on: 2026-10-24

c5 verified · fact 221–304 V

Scope: products CSI-25/30/36/40K-T480GL01-UB; standard CA Rule 21 proposed

Conditions: Volt-Watt V2 (Vstart), Rule 21 settings, 480 V rated grid

verified by: review-workflowverified on: 2026-10-24

c7 drafted · lead 277–332 V

Scope: products CSI-25/30/36/40K-T480GL01-UB; standard CA Rule 21 proposed

Conditions: Volt-Watt V3 (Vstop), Rule 21 settings, 480 V rated grid

default_value

c2 drafted · lead nominal 254 V

Scope: products Solis RHI-1P(5-10)K-HVES-5G-US; standard CA Rule 21 proposed

Conditions: Volt-Watt V2 (Vstart), Rule 21 default, 240 V rated grid

review note: possible conflict with c4 (same source; check the conditions)

c4 verified · fact nominal 264 V

Scope: products Solis RHI-1P(5-10)K-HVES-5G-US; standard CA Rule 21 proposed

Conditions: Volt-Watt V3 (Vstop), Rule 21 default, 240 V rated grid

verified by: review-workflowverified on: 2026-10-24review note: possible conflict with c2 (same source; check the conditions)

c6 drafted · lead nominal 293 V

Scope: products CSI-25/30/36/40K-T480GL01-UB; standard CA Rule 21 proposed

Conditions: Volt-Watt V2 (Vstart), Rule 21 default, 480 V rated grid

review note: possible conflict with c8 (same source; check the conditions)

c8 drafted · lead nominal 304 V

Scope: products CSI-25/30/36/40K-T480GL01-UB; standard CA Rule 21 proposed

Conditions: Volt-Watt V3 (Vstop), Rule 21 default, 480 V rated grid

review note: possible conflict with c6 (same source; check the conditions)

Referenced by

Data