Monthly NMGG Calculator for Solar PPAs in India
This calculator helps you derive monthly NMGG target generation from the annual contractual NMGG defined in your solar PPA.
The Monthly NMGG target generation figures represent the estimated solar energy generation for each month, helping you analyze your system’s seasonal performance and optimize operations.
How to Use This Calculator:
- Enter Contractual NMGG (kWh): This is the Net Minimum Guaranteed Generation target agreed for your solar plant.
- Input Monthly Estimated POA Insolation (kWh/m²): Enter the designed or expected Plane of Array solar insolation values for each month.
- Submit the form: The calculator will synthesize and display the estimated Monthly NMGG target generation values based on your inputs.
The calculated monthly NMGG target generation values help monitor monthly performance against targets to ensure the annual goal is achieved.
What is NMGG in Solar Projects?
Net Minimum Guaranteed Generation (NMGG) is the minimum annual energy generation commitment defined in a solar project’s Power Purchase Agreement (PPA) in India.
It represents the guaranteed net energy output that the plant must deliver over a contract year, after accounting for system design, losses, and site-specific conditions.
NMGG is a contractual metric, not a regulatory mandate. Indian DISCOMs evaluate compliance on an annual basis as per the PPA terms.
Regulatory Context (India)
In Indian solar power projects, Net Minimum Guaranteed Generation (NMGG) is a contractual performance obligation defined inside the Power Purchase Agreement (PPA). It is not specified by MNRE guidelines or CERC regulations.
DISCOMs assess compliance only on an annual basis. Monthly NMGG targets are used internally by asset owners, EPC teams, and O&M providers to monitor performance trends, identify seasonal underperformance, and manage liquidated damage risk well before the contract year ends.
This calculator aligns with common industry practice followed in RESCO, captive, and group captive solar projects across Indian states.
Calculation Logic Used
This calculator distributes the annual Net Minimum Guaranteed Generation (NMGG) across months in proportion to the designed or estimated Plane of Array (POA) insolation profile for the project site.
Monthly target generation is derived by weighting the annual NMGG according to each month’s relative contribution to the total annual POA insolation.
This proportional allocation approach reflects common industry practice followed in Indian solar projects for internal forecasting, performance tracking, and early identification of annual NMGG compliance risk.
Contractual NMGG compliance, however, is evaluated by the DISCOM only on an annual basis as defined in the project’s Power Purchase Agreement (PPA).
Example: Monthly NMGG Calculation
Suppose your 100kW solar plant has an annual NMGG of 150,000 kWh and the monthly POA insolation (kWh/m²) is as follows:
| Month | POA Insolation | Estimated Monthly NMGG (kWh) |
|---|---|---|
| Jan | 175.63 | 13092.84 |
| Feb | 176.52 | 13159.19 |
| Mar | 206.21 | 15372.52 |
| Apr | 194.89 | 14528.63 |
| May | 192.21 | 14328.85 |
| Jun | 163.11 | 12159.50 |
| Jul | 123.98 | 9242.44 |
| Aug | 112.55 | 8390.36 |
| Sep | 143.28 | 10681.22 |
| Oct | 180.72 | 13472.29 |
| Nov | 174.22 | 12987.73 |
| Dec | 168.81 | 12584.43 |
Note: Values shown are illustrative and depend on site-specific POA insolation distribution.
Monthly NMGG Chart
Important Usage Note
Monthly NMGG values generated by this tool are indicative and meant for performance monitoring only. Indian DISCOMs evaluate NMGG compliance strictly on an annual basis as per the PPA.
Shortfalls in individual months do not constitute contractual default unless the annual NMGG obligation is missed, as defined in the PPA.
Tips for Using Monthly NMGG Data
- Monitor seasonal underperformance to detect issues early (soiling, shading, or inverter problems).
- Use monthly targets for maintenance planning and O&M scheduling.
- Compare actual generation with target to anticipate any annual shortfall well in advance.
- Always cross-check POA insolation data against satellite or on-site measurements for accuracy.
Frequently Asked Questions
How do DISCOMs evaluate NMGG compliance in India?
In India, DISCOMs evaluate NMGG compliance during annual energy settlement strictly as per the terms defined in the project’s Power Purchase Agreement (PPA). The assessment is based on net metered energy recorded at the billing meter, not inverter or SCADA generation values.