# What minimum specification should a rooftop solar inverter meet on overload, harmonics, power factor and losses?

Canonical: https://senseible.earth/answers/rooftop-solar-inverter-minimum-spec-overload-thd

The Ministry of New and Renewable Energy (MNRE) specification asks for an inverter with at least 20% overloading capacity, no-load losses under 1% of rated power, harmonic distortion under 3%, power factor above 0.9 lag or lead, and direct current (DC) injection no more than 0.5% of full rated output.

## The numbers in clauses 2.6 and 2.7

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.

- Overloading capacity of minimum 20%.
- No-load losses: less than 1% of rated power.
- Total harmonic distortion (THD): less than 3%.
- Power factor (PF): more than 0.9, lag or lead.
- Should not inject direct current (DC) power more than 0.5% of full rated output at the interconnection point, and comply to IEEE 519, the standard of the Institute of Electrical and Electronics Engineers (IEEE).
- Inverter efficiency (minimum): more than 90% in the case of 10 kilowatts (kW) or below with in-built galvanic isolation.
- Item 2.7(x) names Indian Standard (IS) 17980 for minimum overall efficiency but prints no values; take them from the standard.

## Build and data features

- A maximum power point tracker shall be integrated in the inverter.
- Protection of enclosure: IP-54 (minimum) for indoor and IP-65 (minimum) for outdoor, where IP is the ingress protection rating.
- Ambient temperature considered: -20 to 60 degrees Celsius.
- The inverter should have the inbuilt facility to communicate system related data through a SIM (subscriber identity module) or dongle. It may also be enabled for Wi-Fi.
- Complete automatic operation including wake-up, synchronization and shutdown.
- For a three-phase connection, a single-phase or three-phase inverter is provided as per the consumer's requirement and the regulations of the State.

## Where it ties to your bill

My reading: a power factor above 0.9 is a floor for the inverter, not a cure for your plant's reactive load. If your bill is on kilovolt-ampere hour (kVAh) units and the power factor drops after solar, see the page on that effect. Check the Quality Control Order for solar inverters (clause 2.1 names the one dated 30.08.2017) and the page on inverters above 200 kilowatts for the current certification route.

## Reading the limits for a 50 kW inverter (example size)

- No-load losses under 1%: 50 x 0.01 = under 0.5 kW
- DC injection of no more than 0.5% of full rated output: 50 x 0.005 = no more than 0.25 kW
- Overloading capacity of minimum 20%: 50 x 1.20 = at least 60 kW capability (the clause gives no duration, so ask the maker for one)

The 50 kW size is an example. The percentages are MNRE's.

## What Senseible does here

Senseible reads electricity bills into monthly records, so the units you import month by month sit in one place. Inverter data is a custom integration on request. It does not check an inverter against a standard.

- [Solar inverters above 200 kW and BIS](https://senseible.earth/answers/solar-inverter-bis-certification-above-200-kw)
- [Rooftop solar lowers power factor on a kVAh bill](https://senseible.earth/answers/rooftop-solar-lowers-power-factor-kvah-bill)
- [Factory harmonic distortion limits](https://senseible.earth/answers/harmonic-distortion-limits-factory-thd)
- [Will rooftop solar run in a power cut](https://senseible.earth/answers/rooftop-solar-during-power-cut-islanding)

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](https://mnre.gov.in/static/uploads/2025/08/f20f6d61628866e66b612810b49abd78.pdf)

Last reviewed 2026-11-06. Re-check clause numbers and figures against the current version of the guidelines before you rely on them. The specification text is in Annexure 3, section 2. Inverter certification rules change, so check the current order.