Free Tool · IEC 61724-1 / NREL PVWatts · 8760 Energy Model

AC/DC Loss Analysis

IEC 61724-1 / NREL PVWatts loss cascade calculator for grid-connected solar PV. Enter system size, DC:AC ratio, and loss factors — output includes gross DC energy, each loss waterfall component (kWh + %), net AC at POI, PR, CF, and specific yield.

ⓘ Core methodology applies to any grid-connected generator. PV-specific inputs (bifacial gain, clipping) can be omitted for wind/thermal projects.

GrossDC Soiling Mismatch DCWiring Inverter Clipping ACWiring Transformer Availability NetPOI
Cross-links: BESS Grid Connection · Soil Resistivity · Cable Ampacity · Transformer Sizing
System Parameters

0 = monofacial; 5–15% typical for bifacial modules

Calculate clipping from DC:AC ratio
Loss Factors
Irradiance Input

Annual total or enter monthly profile below

Use monthly irradiance profile
Energy Results
—
MWh
Gross DC / yr
—
MWh
Net AC at POI
—
%
Performance Ratio
—
%
Capacity Factor
—
kWh/kWp
Specific Yield
—
%
Total Losses
Methodology
Loss Cascade Order (IEC 61724-1 / PVWatts)
Gross DC → bifacial gain → soiling → mismatch → DC wiring → inverter → clipping → AC wiring → transformer → availability → Net AC (POI)

Performance Ratio: PR = Net_AC / (Irradiance × DC_capacity) × 100. Capacity Factor: CF = Net_AC / (DC_capacity × 8760). Specific Yield: SY = Net_AC / DC_capacity.

Clipping Model
clipping_% ≈ max(0, DC:AC − 1.0) × 40%

Empirical approximation derived from PVWatts hourly simulations. Clipping occurs when DC exceeds inverter AC rating — excess energy is curtailed at rated output.

Bifacial Gain
Gross_DC = Irradiance × DC_capacity × (1 + bifacial_gain/100)

Bifacial modules capture rear-side irradiance from ground-reflected light. Gain is added to gross DC before other losses are applied. Typical: 5–15% depending on albedo and mounting height.

Related Tools

BESS Grid Connection Soil Resistivity — IEEE 81 Cable Ampacity — Neher-McGrath Transformer Sizing

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FAQ
The loss cascade starts from gross DC energy (irradiance × DC capacity) and subtracts each loss in sequence: bifacial gain, soiling, mismatch, DC wiring, inverter conversion, clipping, AC wiring, transformer, and availability. The result is net AC energy at the point of interconnection (POI). Each loss is shown in both kWh/year and as a percentage of gross DC.
When DC capacity exceeds AC capacity (DC:AC > 1.0), the inverter clips excess power at its rated AC output. This calculator estimates clipping as DC:AC excess ratio × 40% — empirically derived from PVWatts hourly simulations. You can also enter a manual clipping loss % if you have site-specific modeling data.
PR = Net AC energy / (Irradiance × DC capacity), expressed as a percentage. It measures the overall conversion efficiency independent of climate. A PR ≥ 75% indicates a well-performing plant; PR 60–75% warrants investigation; PR < 60% suggests systemic issues (shading, high losses, poor maintenance). PR excludes the resource input — it is purely a system performance metric.
Capacity Factor (CF) = Net AC / (DC_capacity × 8760) — the fraction of theoretical maximum output actually delivered. Specific Yield (SY) = Net AC / DC_capacity — total kWh produced per kWp installed. CF is normalized to a year; SY is not. A 100 kWp plant with SY = 1400 kWh/kWp has CF = 16%.
Bifacial modules capture light on both sides, typically gaining 5–15% more energy vs monofacial. The gain is added to the gross DC energy before other losses are applied. Set bifacial_gain_pct = 0 for monofacial systems. Use site albedo and mounting height to refine the gain estimate.
Yes. The core AC loss methodology (wiring, transformer, availability, inverter efficiency) applies to any grid-connected generator. For wind, enter the AC output of the turbine as "DC" capacity and omit bifacial gain and clipping. For BESS, use the energy throughput model to estimate round-trip losses.