Fortress Power Avalon-ESS-5P3-xx.xP1M4

Name: Fortress Power Avalon-ESS-5P3-xx.xP1M4
Brand: Fortress Power

58.8 kWh · 15 kW · Lithium Ion · direct PV input

UL 9540UL 1741 SBCEC listed · Mar 1, 2024

Overview

CEC Energy Storage System List

Avalon-ESS-5P3-xx.xP1M4: 58.8 kWh nameplate energy; 15 kW continuous; lithium ion; accepts solar panels directly (DC-coupled).

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
Sol-Ark L3 HVR	36.9–55.3 kWh	30–60 kW	Lithium Iron Phosphate	10 years	7
EG4 Electronics PP-16/280A3-18K1-AWLL	43 kWh	10.4–12 kW	Lithium Iron Phosphate	10 years	—
EG4 Electronics PP-16/280A3-18K2-AWLL	43 kWh	20.8–24 kW	Lithium Iron Phosphate	10 years	—
Power Center Duracell	14–42 kWh	5 kW	Lithium Iron Phosphate	—	—
Sol-Ark L3 HV-xxKWH-xxK	36.9–55.3 kWh	30–60 kW	Lithium Iron Phosphate	10 years	—

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

How much energy does the Fortress Power Avalon-ESS-5P3-xx.xP1M4 store?

58.8 kWh nameplate, per the California Energy Commission list.

Is the Avalon-ESS-5P3-xx.xP1M4 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).