Illustration · 60 cells

Solar panelSuntech

Suntech STP305S-A20/Wfb

Name: Suntech STP305S-A20/Wfb
Brand: Suntech

60 cells. Power classes 285–330 W in the CEC list.

CEC listed · Oct 12, 2020UL 61730

Power class

Power (STC)305 WCEC nameplate
Efficiency≈18.7%calculated from area
%/°C Pmax−0.353CEC listing test
PTC / STC92.5%PTC 282 W (CEC)

Power classes

CEC PV Module List (Oct 7, 2026) · Cali-Graf calculation · 10 models

Model	Pmax	Voc, V	Isc, A	Vmp, V	Imp, A	Efficiency	PTC	CEC listed
STP285S-A20/Wfb	285 W	39.10	9.42	31.50	9.05	≈17.5%	263 W	Oct 12, 2020
STP290S-A20/Wfb	290 W	39.30	9.52	31.70	9.15	≈17.8%	268 W	Oct 12, 2020
STP295S-A20/Wfb	295 W	39.50	9.62	31.90	9.25	≈18.1%	272 W	Oct 12, 2020
STP300S-A20/Wfb	300 W	39.70	9.72	32.10	9.35	≈18.4%	277 W	Oct 12, 2020
STP305S-A20/Wfb	305 W	39.90	9.82	32.30	9.45	≈18.7%	282 W	Oct 12, 2020
STP310S-A20/Wfb	310 W	40.10	9.91	32.50	9.55	≈19.0%	287 W	Oct 12, 2020
STP315S-A20/Wfb	315 W	40.30	10.00	32.70	9.64	≈19.3%	292 W	Oct 12, 2020
STP320S-A20/Wfb	320 W	40.50	10.09	32.90	9.73	≈19.6%	296 W	Oct 12, 2020
STP325S-A20/Wfb	325 W	40.70	10.18	33.10	9.82	≈19.9%	301 W	Oct 12, 2020
STP330S-A20/Wfb	330 W	40.90	10.27	33.30	9.91	≈20.2%	306 W	Oct 12, 2020

≈ efficiency = Pmax ÷ CEC-listed area 1.63 m².

Build & dimensions

CEC PV Module List (Oct 7, 2026)

Module area1.63 m² (17.5 ft²)CEC-listed area
Cells60 cells
Back coverBlack backsheet

Heat & cold behaviour

CEC PV Module List (Oct 7, 2026) · Cali-Graf calculation

	CEC listing test
Pmax coefficient γ	−0.353 %/°C
Voc coefficient β	−0.266 %/°C
Isc coefficient α	+0.043 %/°C
Operating cell temperature	NOCT 46.6 °C

Vmp coefficient ≈ γ − α (CEC); used only for the hot-roof voltage estimate.

Away from lab conditions — CEC listing test points

Class	Pmax at NOCT	Vmp × Imp at NOCT	Pmax at 200 W/m²	Low-light efficiency vs STC
285 W	211.3 W	29.95 V × 7.06 A	55.7 W	98%
290 W	215 W	30.14 V × 7.13 A	56.7 W	98%
295 W	218.7 W	30.33 V × 7.21 A	57.6 W	98%
300 W	222.5 W	30.52 V × 7.29 A	58.6 W	98%
305 W	226.3 W	30.71 V × 7.37 A	59.6 W	98%
310 W	230.1 W	30.9 V × 7.45 A	60.6 W	98%
315 W	233.7 W	31.09 V × 7.52 A	61.6 W	98%
320 W	237.3 W	31.28 V × 7.59 A	62.5 W	98%
325 W	241 W	31.47 V × 7.66 A	63.5 W	98%
330 W	244.6 W	31.66 V × 7.73 A	64.5 W	98%

Pmax = Vmp × Imp from the CEC listing; low-light efficiency = Pmax at 200 W/m² ÷ (20% of STC Pmax).

Independent reliability testing

Kiwa PVEL Scorecard

PVEL Scorecards

Suntech named Top Performer, 2014–2024

This exact series is not listed in published PVEL Top Performer tables. Results below are for the manufacturer.

Inverter compatibility & string sizing

CEC PV Module List (Oct 7, 2026) · Cali-Graf calculation · NLR PVWatts v8 · inverter datasheets · NLR SAM inverter library · CEC Grid Support Inverter List (Oct 7, 2026)

CityColdest air, °CHottest cell, °CString inverter

42.3 V

Voc when cold

per panel

26 V

Vmp when hot

per panel

Max panels / string

max DC 600 V

Min panels / string

MPPT from 60 V

Defaults come from NLR TMY weather (coldest hour, hottest modeled cell). Code calculations (NEC 690.7) use the ASHRAE extreme annual minimum, which is usually colder — enter it above. β is the CEC-measured coefficient; NEC 690.7 calculations use the datasheet value.

String inverters most named in SoCal permits

Inverter	Max DC input	MPPT	Window source	Panels per string
Tesla 1538000-xx-y	600 V	60–480 V	datasheet	3–14
Solis (Ginlong) S6-EH1P10K-H-US	600 V	80–520 V	datasheet	4–14
Solis (Ginlong) Solis-1P7.6K-4G-US	600 V	100–500 V	datasheet	4–14
Qcells Q.VOLT H7.6SX	498 V	234–498 V	CEC test window	9–11

Microinverters (one per panel)

Microinverter	Recommended module power	Max DC input	MPPT	Voc cold / Vmp hot	Check	DC/AC
Enphase IQ8PLUS-72-2-US	235–440 W	60 V	29–45 V	42.3 / 26 V	⚠ Works; below MPPT at peak heat	1.05
APsystems (Alt Power System) DS3-L	265–570 W	60 V	28–45 V	42.3 / 26 V	⚠ Works; below MPPT at peak heat	0.39
Enphase IQ8M-72-2-US	260–460 W	60 V	30–45 V	42.3 / 26 V	⚠ Works; below MPPT at peak heat	0.94
Enphase IQ8A-72-2-US	295–500 W	60 V	32–45 V	42.3 / 26 V	⚠ Works; below MPPT at peak heat	0.87

Voltage check against the microinverter datasheets — confirm the pairing on the manufacturer’s module compatibility list. Rows appear only when the panel’s power is inside the microinverter’s recommended module power range.

SolarEdge and other optimizer-based systems size strings by the optimizer rules — use the manufacturer’s designer. Reference inverters: most named in SoCal permits since Oct 2024.

Expected production in Southern California

NLR PVWatts v8 · Cali-Graf calculation

PanelsCity for chartSystem size

City	kWh / kW / yr	kWh / panel / yr	kWh / system / yr	Sun, kWh/m²/day
Los Angeles	1,676	511	11,757	6.08
Palmdale	1,835	560	12,873	6.69
Chula Vista	1,696	517	11,897	6.11
Huntington Beach	1,643	501	11,526	5.89
Riverside	1,696	517	11,897	6.21
Santa Clarita	1,724	526	12,094	6.28

Estimate for comparison, not a quote: shading, roof orientation and local losses change real output. Roof mount, 20° tilt, south, 14% system losses.

Compare with similar 305 W panels

CEC PV Module List (Oct 7, 2026) · JinkoSolar datasheets · Kiwa PVEL Scorecard · building permits

Panel	Pmax	Efficiency	γ Pmax (CEC)	Voc, V	Isc, A	PVEL (product / brand)	SoCal permits (series)
Suntech STP305S-A20/Wfb	305 W	≈18.7%	−0.353	39.9	9.82	brand 6×	—
JinkoSolar JKM310M-60HBL	310 W	≈18.4%	−0.407	40.5	9.92	brand 12× (2014–2026)	45
REC Group REC305NP	305 W	≈18.8%	−0.351	39.9	9.93	brand 9× (2016–2025)	4
Sinotec USA STS-310M3B-60	310 W	≈18.8%	−0.375	40.3	10.04	—	3

Same fields from the same sources for every row; ≈ efficiency is calculated from the listed area. Comparable series: other brands, same product group, power range covering this class.

Questions & answers

How efficient is the Suntech STP305S-A20/Wfb?

Calculated from the panel area (1.63 m²): about 18.7% for the 305 W class. 305 W over 1.63 m² equals about 187 W per square meter.

How much energy does one panel produce in Los Angeles or Palmdale?

PVWatts v8 with typical-year weather gives about 511 kWh per year per 305 W panel in Los Angeles and about 560 kWh in Palmdale (20° roof, facing south, 14% system losses).

How much power does it lose on a hot roof?

With γ = −0.353 %/°C, at a 77 °C cell temperature (hottest modeled hour in Palmdale) output is about 18.3% below the STC rating.

How many panels fit on one string?

With the Tesla 1538000-xx-y (max DC 600 V, MPPT from 60 V, datasheet) in Los Angeles the calculator gives 3–14 panels per string (Voc at 2 °C = 42.3 V, Vmp at 74 °C cell = 26 V). Final design must follow the inverter manual and NEC 690.7.

Has this panel been reliability-tested?

This exact series is not in published PVEL Top Performer tables; Suntech was named a Top Performer in 6 Scorecards (2014–2024).

Sources

California Energy Commission — Solar Equipment Lists, PV Module List, Inverter List (snapshot Oct 7, 2026).
JinkoSolar — datasheet THE MOST DEPENDABLE SOLAR BRAND.
JinkoSolar — manufacturer datasheet “Eagle HC 60M G2 315-335 Watt MONO PERC HALF CELL MODULE”.
Kiwa PVEL — PV Module Reliability Scorecard, Top Performer lists 2014–2024.
NLR (formerly NREL) — System Advisor Model CEC inverter library (version 2026.7.3).
NLR (formerly NREL) — PVWatts v8, NSRDB PSM v3 typical-year weather for Los Angeles, Palmdale, Chula Vista, Huntington Beach, Riverside, Santa Clarita.
Inverter datasheets — APsystems (Alt Power System), Enphase, Solis (Ginlong), Tesla (manufacturer documents).
Building permits — Southern California permit portals. Equipment matched from permit descriptions.
Cali-Graf calculations — formulas and inputs are shown next to each calculated value (efficiency from area, temperature-corrected voltages, string sizing, energy estimates).