Rooftop solar installation in Thailand is growing rapidly, but many projects underperform because of inaccurate yield calculations, unanalysed shading from adjacent structures, and incomplete understanding of EGAT/MEA regulations. Combining BIM with solar simulation resolves all these issues before investment.
BIM Roof Modelling for Solar Analysis
The first step is creating an accurate BIM roof model in Revit or ArchiCAD, including: roof orientation and pitch angle, obstruction positions (water tanks, vents, aerials), and adjacent buildings that may cast shading.
Solar3D or Autodesk Revit Solar Analysis (via the Insight add-on) generates annual solar irradiance maps across the roof surface as colour-coded kWh/m²/year overlays, identifying optimal panel placement zones.
PVsyst: Industry-Standard Solar Simulation
PVsyst is the P50/P90 Energy Yield Simulation standard for Solar PV. Key inputs: location (Bangkok: GHI approximately 1,600–1,800 kWh/m²/year), panel type (monocrystalline, efficiency 20–23%), configuration (string inverter vs. microinverter), and 3D shading scene.
Outputs: Annual Energy Yield (kWh/year), Performance Ratio (PR target >75% for Thai climate), and Specific Yield (kWh/kWp/year, target 1,250–1,450 for Bangkok).
Battery Sizing: Determining Optimal Capacity
Battery capacity selection depends on use case: Self-Consumption Maximisation (storing daytime solar for evening use), Backup Power (supporting 4–8 hour outages), or Peak Shaving (reducing peak demand 17:00–22:00).
Basic sizing formula: Battery Capacity (kWh) = (Nighttime Load kWh × Backup Hours) ÷ (DOD × Round-trip Efficiency). DOD of 80% applies to LFP (LiFePO4) chemistry — recommended for Thailand due to high heat tolerance.
Popular LFP batteries in Thailand: Tesla Powerwall 3 (13.5 kWh, ~USD 10,000), BYD Battery-Box Premium LFP (5–10 kWh, better value), CATL Verge (locally assembled, most cost-effective).
Thai Solar Regulations: VSPP and Net Metering
VSPP (Very Small Power Producer) regulations apply to Solar PV systems up to 1,000 kW, allowing grid connection and excess electricity sale to MEA/PEA at Feed-in Tariff rates set by NEPC.
Net Metering rates (2023–2024): MEA purchases excess residential solar (≤10 kWp) at 2.20 THB/kWh — significantly below the retail purchase rate of 4.50–5.00 THB/kWh. This makes Self-Consumption Maximisation with battery storage a far better strategy than grid export.
ROI Calculation with BIM Data
Example: 200 sqm Bangkok home, 10 kWp monocrystalline plus 10 kWh LFP battery. Installation cost: THB 350,000–500,000. PVsyst P50 annual yield estimate: 14,000–16,000 kWh. Annual electricity bill saving: THB 63,000–72,000 (at 4.50 THB/kWh). Payback period: 5–8 years (before further panel price reductions).