Fortress Power DuraRack DC energy storage system-xx.xP4

Name: Fortress Power DuraRack DC energy storage system-xx.xP4
Brand: Fortress Power

21.5 kWh · 13.8 kW · Lithium Iron Phosphate

UL 9540CEC listed · Jun 11, 2025

Overview

CEC Energy Storage System List

DuraRack DC energy storage system-xx.xP4: 21.5 kWh nameplate energy; 13.8 kW continuous; lithium iron phosphate.

CEC Energy Storage System List

NLR PVWatts v8 · Cali-Graf calculation · CEC Energy Storage System List

Solar array size that refills the battery from empty in one average day, before the home uses any of it (NLR PVWatts v8, 20° south roof).

CEC Energy Storage System List

UL 9540 certifies the whole storage system; UL 9540A is the fire-propagation test that fire codes ask for indoors and near walls.

CEC Energy Storage System List

CEC Energy Storage System List

Battery	Energy	Continuous power	Chemistry	Warranty	SoCal permits
Generac PWRcell	8.6–17.1 kWh	3.4–6.7 kW	Lithium Ion	—	8
Lunar Energy LE-ESS-xxKWH	15–20 kWh	9.6 kW	Lithium Ion	—	3
Panasonic EVHB-I7-Xxx	9–18 kWh	7.6 kW	Lithium Iron	12 years	2
sonnen SCORE-Pxx	10–20 kWh	4.8 kW	Lithium Iron Phosphate	10 years	2
Qcells Q.HOME+ ESS HYB-G1	13.5 kWh	6–8.6 kW	Lithium Ion	10 years	1
EG4 Electronics PP-100A14-18K1-LP	20.5 kWh	10.4–12 kW	Lithium Iron Phosphate	10 years	—

Same segment, similar capacity; each row from the same sources.

How much energy does the Fortress Power DuraRack DC energy storage system-xx.xP4 store?

21.5 kWh nameplate, per the California Energy Commission list.

Is the DuraRack DC energy storage system-xx.xP4 UL 9540 certified?

Yes — the CEC list shows UL 9540 certification (certified by intertek).

California Energy Commission — Energy Storage System List, data as of Oct 7, 2026. Manufacturer-reported values confirmed by CEC against certificates.
NLR (formerly NREL) — PVWatts v8, NSRDB PSM v3 typical-year weather for Los Angeles, Palmdale, Riverside, Santa Clarita, Chula Vista, Huntington Beach.
Cali-Graf calculations — formulas and inputs are shown next to each calculated value (efficiency from area, temperature-corrected voltages, string sizing, energy estimates).