Calculate the optimal solar panel system size based on your daily energy consumption and location. Supports 50+ global locations with accurate solar irradiance data.
Average household: 10-30 kWh/day
Sets peak sun hours, the monthly irradiance profile and the latitude below from the registered NASA POWER dataset path. The starting selection is the nearest listed city, not your site — change it, or override the figures directly.
Annual average hours of peak sunlight per day
Drives the irradiance model, the reported tilt and the row-spacing sun path. Filled from the selected location; left blank the calculation is refused by name.
Starting position 25% — a generic allowance for cloudy days and load growth, not a rule from any standard. Set the margin your project actually uses.
Starting value 20% — a generic lump figure, not this array's measured losses. Expand SYSTEM LOSSES below to itemise it, or set your own project figure here.
Compass degrees: 0° = North, 90° = East, 180° = South, 270° = West
Using tilt 15°, azimuth 180° compass (manual) — POA = 5.36 kWh/m²/day
From the registered NASA POWER dataset path (artifact verification pending). Hover a bar for exact kWh.
- 01Notice: Monthly GHI profile is from the registered NASA POWER dataset path; artifact verification remains pending.
- 02Notice: Per-month clearness index KT[m] = monthly GHI input ÷ H0 (annual mean 0.540); the Erbs diffuse split uses each month's own KT, so the supplied seasonal pattern is preserved.
- 03Notice: Diffuse split uses the Erbs daily correlation applied to the monthly-mean clearness index; hourly distribution uses Collares-Pereira & Rabl (global) and Liu & Jordan (diffuse). Hourly diffuse is bounded by hourly global (Id ≤ I), so a horizontal plane reproduces the input GHI exactly at every clearness index.
- 04Notice: Transposition uses the HDKR anisotropic sky model with isotropic ground reflection.
- 05Notice: Ground albedo ρg = 0.2 (0.2 ≈ ordinary ground, ~0.7 ≈ fresh snow).
- 06Notice: One representative day per month (Klein 1977); leap years averaged via February = 28.25 days.
- 07Notice: panel efficiency 21.0% and 5 m²/kW are the built-in monocrystalline technology preset, not a module datasheet.
- 08Step 1: Apply safety margin (25%)
- 09Required daily production = 20.00 × 1.25 = 25.00 kWh/day
- 10Step 2: Account for system losses (20%, stated by the caller)
- 11Effective POA = 5.36 × derate 0.8000 (20%, stated by the caller) = 4.29 hours (plane-of-array at tilt 15°, azimuth 0°)
- 12Step 3: Calculate system size
- 13System size = 25 kWh ÷ 4.29 h = 5.83 kW
- 14Step 4: Calculate number of panels
- 15Panels needed = 5.83 kW × 1000 ÷ 400W = 15 panels
- 16Actual capacity = 15 × 400W = 6.00 kW
- 17Step 5: Calculate expected production
- 18Annual production = Σ monthly = 9402 kWh (each month at its own POA and derate)
- 19Average daily production = 9402 ÷ 365.25 = 25.74 kWh
- 20Step 6: Calculate roof area
- 21Area required = 6.00 kW × 5 m²/kW = 30.0 m²
- 22Step 7: Tilt angle = 15° (user-specified)
PSH (Peak Sun Hours): Equivalent hours of 1000 W/m² solar radiation per day
System Losses: Includes wiring, inverter, soiling, shading (~14-20% typical)
Safety Margin: Extra capacity for cloudy days and future consumption growth
| Technology | Efficiency | Area per kW | Degradation/year | Warranty | Best For |
|---|---|---|---|---|---|
| monocrystalline | 21% | 5 m² | 0.4% | 25 years | Limited space, maximum efficiency |
| polycrystalline | 17% | 6.5 m² | 0.5% | 25 years | Budget-friendly, good efficiency |
| thin-film | 13% | 8.5 m² | 0.8% | 20 years | Large areas, hot climates |