Which module datasheet numbers should I check before accepting rooftop solar: tolerance, fill factor and temperature coefficient?

The Ministry of New and Renewable Energy (MNRE) specification for residential rooftop systems sets a power tolerance of up to +3%, a minimum fill factor of 75% and a temperature coefficient of power equal to or better than -0.4% per degree Celsius for crystalline modules. It also lists the test standards a module must pass.

Numbers to find on the datasheet

These are clauses from the technical specification in Annexure 3 of MNRE's guidelines for its residential rooftop solar scheme, Pradhan Mantri Surya Ghar: Muft Bijli Yojana. A factory is not bound by them, but they are a published checklist to hold a quotation against.

• Clause 1.3: the rated power of a solar photovoltaic (PV) module shall have maximum tolerance up to +3%.
• Clause 1.8: solar PV modules of minimum fill factor 75%, to be used.
• Clause 1.6: the temperature coefficient of power shall be equal to or better than -0.4% per degree Celsius for crystalline modules and -0.3% per degree Celsius for thin film modules.
• Clauses 1.4 and 1.5: the peak-power point current of any supplied module string shall not vary by 1% (printed as +1%) from the arithmetic mean, and the voltage by 2% (printed as + 2%), for all modules or strings connected to the same maximum power point tracker.

Test standards the specification names

• IEC 61215 or IS 14286 for design qualification of crystalline silicon modules (International Electrotechnical Commission, IEC; Indian Standard, IS).
• IEC 61853 Part 1 or IS 16170 Part 1 for performance testing and energy rating.
• IS/IEC 61730 Parts 1 and 2 for module safety.
• IS 17210 Part 1 or IEC 62804-1 for the test that detects potential-induced degradation.
• For thin film modules, IS 16077:2013 or IEC 61646:2008.

Labels you can check on the roof

• Clause 1.12: the actual power output, Pmax (maximum power at standard test conditions), is on the label on the back of the module; the maximum system voltage is on the back sheet.
• Clause 1.13: unique serial number, model number, maker, manufacturing year, Make in India logo and wattage are displayed inside the laminated glass.
• Clause 1.7: module capacity adheres to the Approved List of Models and Manufacturers (ALMM) order. See the ALMM page on this site for factories.

Why the temperature number matters

Datasheet power is normally quoted at standard test conditions, which use a 25 degrees Celsius cell temperature (general practice, not printed in the cited clauses). A module on a hot factory roof can run far hotter, and the coefficient tells you how much power you lose for each degree above 25. A thin film module with -0.3% loses less than a crystalline one with -0.4% at the same heat.

A hot roof afternoon (example module)

• Datasheet power: 540 watts at 25 degrees Celsius
• Cell temperature on the roof: 65 degrees Celsius (an example, so 40 degrees above 25)
• Crystalline at -0.4%: 40 x 0.4 = 16% loss, so 540 x 0.84 = 453.6 watts
• Thin film at -0.3%: 40 x 0.3 = 12% loss, so 540 x 0.88 = 475.2 watts

Module power and cell temperature are example numbers. The two coefficients are MNRE's limits.

What Senseible does here

Senseible reads electricity bills into monthly records, so the units you import month by month sit in one place. It does not read datasheets or check module quality.

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Sources: Ministry of New and Renewable Energy (MNRE), Guidelines for PM-Surya Ghar: Muft Bijli Yojana, Central Financial Assistance to Residential Consumers, with Annexures 2 to 4

Last reviewed 2026-11-06. Re-check clause numbers and figures against the current version of the guidelines before you rely on them. Clause numbers are from the technical specification in Annexure 3. Standards are revised, so check the current edition.