Commercial rooftop solar in Vietnam: rules and delivery

The economics of rooftop solar come from self-consumption: every kWh generated and used on site replaces one kWh bought from the grid at the industrial or commercial retail tariff, so returns are highest when daytime load overlaps with solar hours.

Factories, cold stores, textile, plastics and steel plants and shopping centres usually have large roofs, adequate structural capacity and stable daytime load — exactly the conditions for a high self-consumption ratio without relying on exports.

• Lower energy cost at the retail tariff applied to production and commercial customers, especially in daytime peak blocks.
• A hedge against retail tariff increases across the 20–25 year life of the system.
• Verifiable renewable generation data for ESG reporting, GHG inventories and group-level RE100 roadmaps.
• Lower roof surface temperature under the module field, improving working conditions below.

Rooftop solar for self-production and self-consumption is governed by Decree 58/2025/ND-CP (effective 3 March 2025), which details the Electricity Law on renewable and new energy development. Read it before fixing capacity and the grid connection approach.

• Buildings that comply with investment, construction, land, environmental, safety and fire-protection rules may install rooftop solar for self-production and self-consumption.
• Systems connected to the national grid may sell surplus energy, but not more than 20% of the energy generated at the source output (measured at the inverter output, including energy passing through storage if any).
• The surplus purchase price is the previous year's average market energy price published by the system and market operator, capped by the maximum of the corresponding generation price bracket.
• Documentation, development procedures, connection agreements and commissioning follow the Decree and guidance from MOIT and EVN.

Legal content is reference information as of the publication date and does not replace project-specific legal advice.

A common mistake is sizing by available roof area. The correct approach is to analyse 15-minute interval data or 12 months of bills to find the capacity at which almost all generation is consumed on site, minimising exports.

• Collect hourly/daily load data and separate working days, weekends and holiday shutdowns.
• Simulate yield with local irradiation data (PVsyst) and overlay it on the daytime load curve.
• Check roof load capacity, sheet age, orientation and pitch, and shading from stacks, cooling towers and neighbouring roofs.
• Where load is concentrated at night or drops at weekends, consider adding BESS instead of more modules.

Specific yield for rooftop systems in Vietnam typically falls in the range of roughly 1,100–1,400 kWh per kWp per year — higher in the south-central region, the Central Highlands and the south, lower in the north. Reference irradiation data is available from the World Bank Group's Global Solar Atlas.

• Module degradation over time (commonly published at around 0.4–0.55% per year depending on product and warranty).
• Temperature losses, soiling, partial shading and losses in cabling and transformers.
• Output curtailment from zero-export settings when the system is designed purely for self-consumption.
• Downtime for maintenance, grid outages or adverse weather.

These ranges are industry reference values for preliminary studies; committed yields must come from a simulation of the actual site, layout and equipment.

• Step 1 – Survey and data analysis: roof, structure, existing electrical system, load profile, connection point.
• Step 2 – Design and simulation: module layout, single-line diagram, inverter selection, yield and financial modelling.
• Step 3 – Documentation: filings under Decree 58/2025/ND-CP, connection agreement, fire protection, construction insurance.
• Step 4 – Construction and commissioning: installation, testing, trial run, acceptance and energisation.
• Step 5 – O&M and monitoring: remote performance monitoring, module cleaning, preventive maintenance, monthly performance reporting.