| Month | kWh/kWp | Unshaded kWh | With shadow kWh | Loss kWh | Loss % |
|---|
Severe, shifting shade throughout the day on a completely off-grid system is one of the toughest solar design problems. A cheap string inverter will let one shaded panel choke the rest of the string. Roof microinverters fix that isolation, but off-grid they add cost and a DC–AC–DC battery penalty. This page answers the hardware question for this roof and this climate, using the live Sumba Roof layout and the moving pyramid shadow — not a generic catalogue answer.
Ranked most practical to most advanced. Click a card to run that architecture through the live shadow model.
| Architecture | Shade isolation | Cost | Battery path | Today kWh | Into battery | Annual into battery | vs best |
|---|
Geometric shade is still the moving pyramid on the Sumba Roof tab. What changed is the electrical use of that shade. Each panel gets a remaining-light fraction f (1 = fully lit, 0 = fully covered). Architectures then combine those fractions differently:
Wiring groups are assigned spatially — north-to-south rows, west-to-east — so neighbouring modules share a string the way they would on the roof. On the Sumba Roof tab, those groups are colour-coded when a string architecture is selected.
| Project | East Nusa Tenggara |
| Location | Pantai Lai Liang, East Nusa Tenggara, Indonesia |
| Coordinates | −9.752674°, 119.504000° |
| Time zone | UTC+08, Asia/Makassar (WITA) |
| Elevation | 24 m |
| Report generated | 05 Jun 2026 |
| System size | 1 kWp |
| Tilt of PV panels | 14° |
| Azimuth of PV panels | 0° (North) |
| Direct normal irradiation (DNI) | 1944.9 kWh/m² |
| Global horizontal irradiation (GHI) | 2080.3 kWh/m² |
| Diffuse horizontal irradiation (DIF) | 691.3 kWh/m² |
| Global tilted irradiation at optimum angle | 2134.4 kWh/m² |
| Air temperature (TEMP) | 26.6 °C |
| Optimum tilt of PV modules | 14° |
| Month | PVOUT specific (kWh/kWp) | PVOUT total (kWh) | DNI (kWh/m²) |
|---|
| Mean air temperature (2 m) | — |
| Mean total cloud cover | — |
| Month | Air temperature (°C) | Cloud cover (%) |
|---|
| Term | Meaning |
|---|---|
| kWp | Kilowatt-peak — rated DC capacity of the array at Standard Test Conditions (1000 W/m², 25 °C, AM 1.5). A measure of system size. |
| kW | Kilowatt — instantaneous power right now (varies with sun and weather; usually below kWp). |
| kWh | Kilowatt-hour — energy = power × time. What is actually generated/billed. |
| Specific yield | Energy per installed capacity, kWh/kWp (usually per year). Size-independent performance score for the site + design. |
| Panel efficiency | Fraction of 1000 W/m² a panel converts to electricity at STC. Here used to turn m² into kWp: 1 m² × 1000 W/m² × eff = eff kWp. |
| System efficiency / Performance ratio (PR) | Combined real-world losses (inverter, wiring, temperature, soiling). Applied in SunCalc mode only — GSA PVOUT already includes it. |
| STC | Standard Test Conditions: 1000 W/m² irradiance, 25 °C cell temperature, AM 1.5 spectrum. |
| Term | Meaning |
|---|---|
| PVOUT | Photovoltaic power output. PVOUT_specific is kWh/kWp; PVOUT_total is kWh for the whole system (AC, after losses). |
| DNI | Direct Normal Irradiation — beam sunlight on a surface pointed straight at the sun (kWh/m²). |
| GHI | Global Horizontal Irradiation — total (beam + diffuse) on a flat horizontal surface. |
| DIF | Diffuse Horizontal Irradiation — scattered sky light (no direct beam). |
| GTI / GTI_opta | Global Tilted Irradiation on the panel plane; GTI_opta is at the optimum fixed tilt. |
| Solar altitude (α) | Angle of the sun above the horizon (0° at horizon, 90° overhead). |
| Solar azimuth / bearing (β) | Compass direction of the sun: 0° = N, 90° = E, 180° = S, 270° = W. |
| Zenith angle (z) | Angle from straight up: z = 90° − α. |
| Air mass (AM) | Relative path length of sunlight through the atmosphere (1 at the zenith, larger when the sun is low). |
| Incidence angle | Angle between the sunbeam and the panel's normal (perpendicular). 0° = sun square-on. |
| Azimuth / Tilt (panel) | Compass direction the panel faces / its slope from horizontal. |
| Sky factor | Manual clear-to-overcast multiplier (100%–20%) used only in SunCalc mode. |
Sun position comes from the SunCalc library for this site's latitude/longitude. SunCalc gives azimuth measured from south; it is converted to a compass bearing:
A direction bearing is turned into an (x = east, y = north) vector with x = sin(bearing), y = cos(bearing).
When the model is set to SunCalc, beam irradiance is estimated from sun geometry and a clear-sky atmosphere:
Note: this is a beam-only clear-sky estimate. It does not add diffuse or ground-reflected light, so SunCalc mode is a geometric comparison rather than a climate measurement — use GSA mode for realistic energy.
GSA mode uses the Global Solar Atlas monthly-hourly PVOUT profile for this exact site (1 kWp reference, azimuth 0° N, tilt 14°). The hourly value is average AC power output (Wh per kWp per clock-hour), already including climate and system losses.
The Annual tab uses the full Sumba Roof configuration and the GSA monthly profile.
Reference loss chain from the AUS/PVsyst EPC proposal for this site (Astronergy 635 W bifacial, Deye 80 kW hybrid inverter, 257 kWh battery). It shows where energy is lost between the available sunlight and the electricity finally delivered. Green = gain, red = loss; the bar shows the energy remaining at each step.
PR (Performance Ratio) is the fraction of the theoretical STC energy that is actually delivered — it bundles every loss below into one number. The dominant loss here is temperature (−8.2%), typical for a hot tropical site. Battery round-trip losses (~5%) only apply to off-grid/stored energy. The Off-grid tab adds shade-mismatch and DC-vs-AC battery-path losses on top of this chain.
The Off-grid tab models how wiring topology uses the same geometric shadow. Default is DC Optimizers (Tigo / SolarEdge) on a 48 V or HV hybrid — panel-level isolation without leaving DC. Parallel micro-strings (2-panel groups) are the low-cost alternative. AC-coupled Enphase is panel-level but pays an extra ~10% into the battery. A single long string inverter is shown only as the failure case.