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Solar Power System Design & Pricing Calculator

Size the PV array, inverter, battery and cables for residential or C&I solar — with map-based solar resource, P50/P75/P90 probability yield, and full-cost economics (LCOE, payback, IRR, NPV).

Start Calculating

Standard

Application *

System AC capacity (kW) *

Daily energy / backup (kWh)

Module power (Wp)

Peak sun hours (kWh/m²/day)

Search city / place

Search a place or click the map — fills latitude and solar resource automatically.

Site latitude (°)

Grid tariff ($/kWh)

Backup days

Storage duration (h)

Grid voltage

Installation (% of equipment)

Probability basis

P50 = median year; P75/P90 are bankable exceedance levels from interannual solar variability.

Advanced parameters

Defaults match the standard design baseline — adjust for site-specific conditions.

DC cable length (m)

DC cable start section (mm²)

Module length (mm)

Module width (mm)

Min design temperature (°C)

Max design temperature (°C)

Battery C-rate limit (0.5–1.0)

Estimate CO₂ savings

Discount rate (WACC)

O&M cost ($/kW/yr)

EPC / soft cost (%)

Project lifetime (yr)

Inverter replacement year

Inverter replacement ($/W)

Module degradation (/yr)

How it works

Pick the application and enter the system size. The calculator designs the string, inverter and battery, sizes the DC cable for voltage drop, and estimates annual yield — then prices the BOM and runs a full-cost economic model.

Worked Examples

Example 1 — 200 kW C&I Grid-Tie Solar (10 kV) · FOB $78,739

Solar system · iec standard · P50/P75/P90

333,461 kWh/yr (P50)

PR 0.846 · P75 324,471 · P90 316,361 kWh/yr

LCOE (full-cost)

$0.0620/kWh

Payback

4.9 yr

Est. total (FOB)

$78,739

💰 Full-cost economics (P50)

Parameter	Value
LCOE	$0.0620/kWh (O&M + WACC + inverter replacement + degradation)
Simple payback	4.9 yr
IRR / NPV	19.8% / $165,229
DSCR	2.31

☀️ Generation (P50/P75/P90)

Parameter	Value
P50 yield	333,461 kWh/yr
P75 yield	324,471 kWh/yr
P90 yield	316,361 kWh/yr (bankable)
Interannual CV	4.0% · climatology (typical interannual CV assumption)

📦 Bill of Materials (example)

Equipment	Model	Spec	Qty
PV Modules	—	550Wp Mono	437
String Inverter	—	110kW + 100kW	2
DC Combiner Box	—	17 inputs	1
DC Distribution Panel	—	QDTB	1
PV Mounting	—	color-steel / flat roof · tilt 25.9°	1
DC Cable PV1-F 6mm²	—	ΔU 0.2% @ 30m	525
MC4 Connector	—	male/female pair	471
AC Cable	—	YJV 4x150	180
Cable Tray	—	hot-dip galvanized	30
DC Surge Protector	—	40kA 1000V	4
Protection Relay	—	OC/instantaneous/anti-islanding	1
SCADA Monitoring	—	plant-level	1
Earthing System	—	flat bar + rods	1
Step-Up Box Substation	—	250kVA 10kV	1
HV Switchgear	—	KYN28-12	1
Ring Main Unit	—	SF6 630A	1

Summary
Estimated total (FOB Qingdao, EXW) — priced equipment			$78,739

📐 Single-line diagram

⚙️ Electrical schematic (protection & metering)

⛳ Grounding grid layout

🔌 Cable schedule & routing

🗄 Switchgear arrangement

🛡 Protection configuration

📋 Protection settings

Circuit	Protection	Setting	Time	Standard
PV string (DC)	gPV fuse	20 A	inst	IEC 60269-6
DC side	SPD (surge)	Type 2 - 40 kA	inst	IEC 61643-11
Inverter AC output	50/51 + anti-islanding	318 A	0.1 s	IEEE 1547 / IEC 62116
Step-up transformer 250 kVA	87 differential	58 A	inst	IEEE C37.91 / GB/T 14285
Step-up transformer 250 kVA	50/51 overcurrent	347 A	0.3 s	IEC 60255-151
Grid interconnection (POI)	anti-islanding / ROCOF	per grid code	per grid code	IEEE 1547 / IEC 61727

Settings are illustrative starting points — confirm with a protection coordination study per IEC 60255 / IEEE 242.

📚 Calculation book

CALCULATION BOOK

Solar cni-grid - 240 kWp - iec - illustrative

1. PV array

Standard: IEC 62548 (PV array design)

Parameter	Formula	Value
Array capacity	Ppv = kW x oversize	240 kWp
Modules	N = Ppv / Wmodule	437 pcs
Strings	S = N / ns	17 strings

2. String design (temp-corrected)

Standard: IEC 60364-5-52

Parameter	Formula	Value
Modules/string range	nMin - nMax	6 - 27 modules
Cold Voc	Voc x ns @ Tmin	55.4 V
Hot Vmp	Vmp x ns @ Tmax	36.6 V

3. DC voltage drop

Standard: IEC 60364-5-52

Parameter	Formula	Value
DC drop	dU = I x L x R / V	0.2% (<= 2%)
DC cable	section	6 mm2 PV1-F

4. AC interconnection

Standard: IEEE 1547 / IEC 61727

Parameter	Formula	Value
Output current	I = P / (sqrt(3) x V)	289 A
Interconnection	voltage level	step-up to 10 kV (250 kVA box sub)

5. Performance & generation

Standard: IEC 61724 (PV monitoring)

Parameter	Formula	Value
Performance ratio	PR = product of losses	0.846
Annual yield (P50)	Ppv x H x 365 x PR	333,461 kWh/yr
P90 (bankable)	P50 x (1 - 1.282 x CV)	0 kWh/yr

This calculation book is illustrative values consolidate the computed results with the referenced standards. A licensed engineer must verify and seal final design documents.

🔧 Secondary schematic (control & signal)

🔩 Terminal strip (typical)

📏 Standard basis (依据标准)

Topic	Standard
Standard basis	IEC
DC cable ampacity	IEC 60364-5-52 Table B.52.2–B.52.5 (copper, 3 loaded conductors, 30°C ambient, PVC) — typical/rounded values, conservative (±3%)
Voltage-drop limit	IEC 60364-5-52 Annex G (DC drop ≤ 2%)
String temp correction	IEC 60364-5-52 (temp -10°C / 60°C)
Units	mm²

🧮 How it was calculated

1. PV capacity: 200kW x 1.2 = 240.0 kWp

2. Inverter: 110kW + 100kW (parallel)

3. String design: 17 strings x ~26 modules (temp-corrected 6-27/string)

4. DC voltage drop: 0.2% (PV1-F 6mm², 30m run)

5. Mounting: tilt 25.9° · row spacing 3.4m

6. Performance ratio (PR): 0.98 soiling x 0.97 mismatch x 0.98 wiring x 0.987 inverter x 0.92 temp = 0.846

7. Output current: ~ 289A (3-ph 400V)

8. Interconnection: step-up 10kV (box sub 250kVA)

9. LCOE (full-cost): $0.0620/kWh over 25 yr (O&M + WACC + inverter replacement + degradation)

10. Turnkey cost: FOB 78,739 → installed 152,048 (42% soft + 12% landing)

11. Payback / IRR / NPV: 4.9 yr · IRR 19.8% · NPV $165,229 · DSCR 2.31

Example 2 — 10 kW Residential Grid-Tie Solar · FOB $3,282

Solar system · iec standard · P50/P75/P90

15,860 kWh/yr (P50)

PR 0.836 · P75 15,433 · P90 15,047 kWh/yr

LCOE (full-cost)

$0.0686/kWh

Payback

5.4 yr

Est. total (FOB)

$3,282

💰 Full-cost economics (P50)

Parameter	Value
LCOE	$0.0686/kWh (O&M + WACC + inverter replacement + degradation)
Simple payback	5.4 yr
IRR / NPV	17.6% / $6,433
DSCR	2.08

☀️ Generation (P50/P75/P90)

Parameter	Value
P50 yield	15,860 kWh/yr
P75 yield	15,433 kWh/yr
P90 yield	15,047 kWh/yr (bankable)
Interannual CV	4.0% · climatology (typical interannual CV assumption)

📦 Bill of Materials (example)

Equipment	Model	Spec	Qty
PV Modules	—	550Wp Mono	24
Grid-Tied String Inverter	—	10kW	1
PV Mounting (rooftop)	—	13kWp · tilt 25.9°	1
DC Cable PV1-F 4mm²	—	ΔU 0.5% @ 30m	36
MC4 Connector	—	male/female pair	28
DC Surge Protector	—	40kA 1000V	2
AC Distribution Box	—	breaker/SPD/anti-islanding	1
Monitoring Module	—	WiFi/4G APP	1
Mounting Accessories	—	clamps/bolts/earthing	24

Summary
Estimated total (FOB Qingdao, EXW) — priced equipment			$3,282

📐 Single-line diagram

⚙️ Electrical schematic (protection & metering)

⛳ Grounding grid layout

🔌 Cable schedule & routing

🗄 Switchgear arrangement

🛡 Protection configuration

📋 Protection settings

Circuit	Protection	Setting	Time	Standard
PV string (DC)	gPV fuse	20 A	inst	IEC 60269-6
DC side	SPD (surge)	Type 2 - 40 kA	inst	IEC 61643-11
Inverter AC output	50/51 + anti-islanding	15 A	0.1 s	IEEE 1547 / IEC 62116
Grid interconnection (POI)	anti-islanding / ROCOF	per grid code	per grid code	IEEE 1547 / IEC 61727

Settings are illustrative starting points — confirm with a protection coordination study per IEC 60255 / IEEE 242.

📚 Calculation book

CALCULATION BOOK

Solar res-grid - 13 kWp - iec - illustrative

1. PV array

Standard: IEC 62548 (PV array design)

Parameter	Formula	Value
Array capacity	Ppv = kW x oversize	13 kWp
Modules	N = Ppv / Wmodule	24 pcs
Strings	S = N / ns	2 strings

2. String design (temp-corrected)

Standard: IEC 60364-5-52

Parameter	Formula	Value
Modules/string range	nMin - nMax	3 - 18 modules
Cold Voc	Voc x ns @ Tmin	55.4 V
Hot Vmp	Vmp x ns @ Tmax	36.6 V

3. DC voltage drop

Standard: IEC 60364-5-52

Parameter	Formula	Value
DC drop	dU = I x L x R / V	0.5% (<= 2%)
DC cable	section	4 mm2 PV1-F

4. AC interconnection

Standard: IEEE 1547 / IEC 61727

Parameter	Formula	Value
Output current	I = P / (sqrt(3) x V)	14 A
Interconnection	voltage level	380 V direct

5. Performance & generation

Standard: IEC 61724 (PV monitoring)

Parameter	Formula	Value
Performance ratio	PR = product of losses	0.836
Annual yield (P50)	Ppv x H x 365 x PR	15,860 kWh/yr
P90 (bankable)	P50 x (1 - 1.282 x CV)	0 kWh/yr

This calculation book is illustrative values consolidate the computed results with the referenced standards. A licensed engineer must verify and seal final design documents.

🔧 Secondary schematic (control & signal)

🔩 Terminal strip (typical)

📏 Standard basis (依据标准)

Topic	Standard
Standard basis	IEC
DC cable ampacity	IEC 60364-5-52 Table B.52.2–B.52.5 (copper, 3 loaded conductors, 30°C ambient, PVC) — typical/rounded values, conservative (±3%)
Voltage-drop limit	IEC 60364-5-52 Annex G (DC drop ≤ 2%)
String temp correction	IEC 60364-5-52 (temp -10°C / 60°C)
Units	mm²

🧮 How it was calculated

1. PV capacity: 10kW x 1.3 = 13.0 kWp

2. Module count: 13000Wp / 550W = 24 pcs

3. String design: 2 strings x ~12 modules

4. String limits: temp-corrected 3-18 modules/string (Voc 55.4V cold / Vmp 36.6V hot)

5. DC voltage drop: 0.5% (PV1-F 4mm², 30m run)

6. Mounting: tilt 25.9° · row spacing 3.4m

7. Performance ratio (PR): 0.98 soiling x 0.97 mismatch x 0.98 wiring x 0.975 inverter x 0.92 temp = 0.836

8. Inverter: nearest rating 10kW

9. LCOE (full-cost): $0.0686/kWh over 25 yr (O&M + WACC + inverter replacement + degradation)

10. Turnkey cost: FOB 3,282 → installed 7,352 (50% soft + 12% landing)

11. Payback / IRR / NPV: 5.4 yr · IRR 17.6% · NPV $6,433 · DSCR 2.08

How it was calculated

Sizing basis

Annual yield = DC capacity × peak sun hours × 365 × performance ratio; P75/P90 = P50 × (1 − 0.674/1.282 × CV) from interannual irradiance; LCOE is full-cost — (CAPEX + Σ(O&M + inverter replacement) discounted) ÷ Σ(generation discounted).

Applicable standards

The design follows IEC 60364-5-52 (or NEC) for DC cable ampacity and voltage drop, with the inverter MPPT window verified by temperature-corrected string voltage; each output is annotated with its standard reference.

Frequently asked questions

What is the difference between P50, P75 and P90 solar yield?

P50, P75 and P90 are exceedance-probability energy estimates accounting for interannual weather variability. P50 is the median year (50% chance of exceeding), P90 is exceeded in 90% of years and is the conservative 'bankable' value lenders require. With a typical interannual CV of 4-6%, P90 is roughly 7-10% below P50. The calculator reports all three plus LCOE.

How is LCOE calculated for a solar system?

LCOE divides lifetime discounted costs (capex, O&M, WACC financing, inverter replacement, module degradation) by lifetime discounted energy. The calculator uses a full-cost model: 25-year life, 0.5%/yr module degradation, WACC around 6-8%, and O&M about 1-1.5% of capex yearly. A 200 kW C&I system in a 4.5 sun-hour site typically lands near $0.04-0.06/kWh.

What tilt angle maximizes annual PV yield?

For a fixed-tilt array, annual yield is near-optimal when tilt equals the site latitude, typically latitude minus 5-15 degrees in low latitudes to favour summer load, or latitude plus 10-15 degrees for winter-heavy or off-grid loads. At 30 deg latitude the optimum is roughly 25-35 degrees. The calculator's yield model accounts for tilt, azimuth and local irradiation.

How many kWh per year does a 100 kW solar system generate?

Annual energy is roughly system kW x peak-sun-hours x performance ratio. A 100 kW array in a 4.5 sun-hour region with a PR of 0.78-0.82 yields about 100 x 4.5 x 365 x 0.80 = 131,000 kWh/yr. In sunnier regions (5.5-6 sun-hours) the same plant reaches 160,000-175,000 kWh/yr. The calculator computes P50/P75/P90 from these inputs.

What battery capacity do I need for night-time backup?

Battery capacity = daily night-time load kWh divided by depth of discharge, times autonomy days. For a 40 kWh nightly load with lithium at 80% DoD and one-day autonomy you need about 50 kWh. Add 15-20% for round-trip losses (AC-coupled ~85-90% efficiency). The configurator sizes the bank, matching PCS and cell chemistry automatically.

Off-grid vs grid-tie — which solar configuration is cheaper?

Grid-tie is 30-50% cheaper because it omits batteries and the backup inverter. A 10 kW grid-tie system runs roughly $8,000-12,000 FOB, while an equivalent off-grid system with 20-30 kWh storage and a hybrid inverter costs $18,000-28,000. Off-grid makes sense only where grid connection is absent or very expensive; the calculator prices both scenarios.

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Results are engineering estimates for reference. Final design must be confirmed by a licensed local engineer against site conditions and applicable codes. Prices are FOB Qingdao (EXW) and do not include freight, duty or installation.

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