Solar Generation Per Day: Is Your Kerala Plant Producing Enough?
Solar generation per day on a Kerala rooftop is never the same two days running, so the useful question is whether your plant is doing its job over weeks and months. Here is where to read your units, the official planning yardstick, how fast panels are allowed to age, and who must fix a plant that falls short.
Quick answer: Read the generation line on your KSEB bill or the RG meter, keep a monthly log, and compare each month with the same month in earlier years. KSERC plans net-metered plants at a 19% capacity utilisation factor, about 4.6 units per kW a day averaged over a year. For PM Surya Ghar plants, the vendor must repair or replace under-performing parts free during the 5-year maintenance period.
Where to read your plant's units
Your plant's output is counted on the renewable generation meter, or RG meter, which KSERC defines as the energy meter installed and used to measure the renewable energy generation from your system (Regulation 3(82)). KSEB reads it together with the net meter on the regular billing cycle (Regulation 28.2). Each prosumer bill must then show the units the RG meter recorded in that billing period, with the opening and closing readings (Regulation 28.3(i)). That printed figure is the official count of what your roof produced.
For plants installed under PM Surya Ghar, MNRE's minimum technical specifications say the inverter should have a built-in facility to send system data through a SIM or dongle, and it may also offer Wi-Fi (Annexure 3, clause 2.7(xiv)). Among planned portal upgrades, the scheme guidelines say the National Portal will receive generation data from connected inverters or smart meters, and that a vendor who receives your plant's data through a SIM, dongle or Wi-Fi must give the portal access to it (Section 8(a)(ix)).
The inverter screen or phone app is handy for a quick look in the evening, but the meter and the bill are the figures KSEB works from. If the app and the meter drift far apart over a whole billing period, write both down and ask your installer to check the inverter's settings and its data connection.
How those two meter faces look in person is covered in our guide to reading solar net meter displays.
What solar generation per day looks like in Kerala
No official figure says what one particular roof must produce, because shade, tilt, dust and weather differ from house to house. The closest official yardstick is a planning figure. To estimate the storage that larger net-metered plants need, KSERC reckons a solar plant's generation potential at a capacity utilisation factor (CUF) of 19% (Regulation 16.9). CUF is the plant's actual output as a share of what it would make running at full rated capacity every hour of the year, and plant capacity here means the inverter's AC rating in kW (Regulation 3(73)). As an example of the arithmetic only: 19% of 24 hours is about 4.6 hours, so a 1 kW plant at that CUF averages about 4.6 units a day across a full year, or roughly 1,660 units a year. It is a yardstick for a whole year, not a target for any single day or a guaranteed output for your roof.
Day-to-day numbers swing with the weather. A spell of heavy monsoon cloud can pull a whole week down, and bright dry weeks lift it again. Judge the plant on complete months, and compare a month with the same month in an earlier year rather than with the month just before it.
If your installer's proposal listed an expected yearly or monthly output, keep that page with your log. It was worked out for your roof, your shade and your equipment, so it is a fairer comparison than any general figure.
Keep a simple monthly generation log
- Pick one day each month and note the RG meter reading, or copy the generation figure printed on each KSEB bill.
- Write the inverter or app total beside it, so you can see whether the two move together.
- Add a short note on the weather, any power cuts, panel cleaning, and new shade from trees, water tanks or nearby buildings.
- Compare each month with the same month in earlier years.
- Keep the log with your installation papers and warranty cards, so you can show it to your installer if output falls.
A log turns a vague feeling that the plant seems weaker into dates and readings an installer can act on. It also shows slow problems early, such as a coconut palm or a neighbour's new floor creeping into the afternoon sun.
How much output loss is normal as panels age
Some decline over the years is built into every panel. MNRE's minimum technical specifications for PM Surya Ghar set the limits below for nominal power output at standard test conditions (STC), the fixed laboratory conditions used to rate panels (Annexure 3, clause 1.9). A small drop from one year to the next is expected; a sudden fall is a fault to report, not ageing.
Minimum panel output allowed by MNRE's PM Surya Ghar specifications
| Period | Nominal power output at STC |
|---|---|
| First year after installation | More than 97% |
| First 10 years | More than 90% |
| Next 15 years | More than 80% |
| Yearly degradation | Below 0.5% per annum |
Separately, the module manufacturer should warrant the panels for not less than five years from commissioning against defects and failures due to manufacturing or quality of materials, and against non-conformity to specifications caused by faulty manufacturing or inspection. A failed module is to be repaired or replaced, and replaced without any cost to the end consumer during that warranty period (Annexure 3, clause 1.10). The vendor must hand you the warranty cards of the solar panels and the inverter (Annexure 2, clause 7). Those cards are the papers you claim against.
The 75% performance ratio rule for PM Surya Ghar plants
MNRE's model consumer-vendor agreement for PM Surya Ghar sets a performance test for the plant. The performance ratio (PR) must be 75% when the DISCOM, which is KSEB in most of Kerala, or its authorised agency commissions the plant. The vendor must bring a radiation sensor with a valid calibration certificate from an NABL or international laboratory for commissioning or testing, and must maintain that PR until the end of the project warranty, which is 5 years from commissioning (Annexure 2, clause 18). Because PR is checked against sunlight measured on site, it tells a weak plant apart from a cloudy month.
The guidelines call Annexure 2 a suggested sample and say the actual agreement may vary case to case (Section 6(d)), so read what your own signed agreement says. The main guideline text is firmer. Registered vendors must provide repairs and maintenance free of cost for the 5-year Comprehensive Maintenance Contract (CMC) period from commissioning, and non-performing or under-performing system components are to be replaced or repaired free of cost in that period (Section 7(d)).
If your plant was not installed under PM Surya Ghar, or those first years are over, the same habit still helps. Compare your log with the output your installer estimated, and raise a clear, dated complaint with the installer when the gap stays for several months. The subsidy path itself is covered in our PM Surya Ghar Kerala guide.
What to do if your solar output drops
- Rule out the simple causes first: a cloudy spell, a recent power cut, or new shade on the panels.
- Look at the inverter screen or app for a warning or fault message. Do not open the inverter cover.
- Never climb onto a wet, mossy or sloping roof to look at the panels, and never touch the DC cables or connectors.
- If the panels look dirty, follow the cleaning method in your manual or ask the installer to clean them.
- Switch the system off only in the way the installer or the manufacturer's manual describes.
- Call the installer for any burning smell, sparking, tripping or a dead inverter, and keep everyone away from the equipment until help arrives.
MNRE's specifications say an operation and maintenance manual, with the do's and don'ts of the plant and step-by-step maintenance and troubleshooting procedures, should be supplied with the plant (Annexure 3, clauses 10.1 to 10.4). The model agreement asks the consumer to report any malfunctioning of the plant to the vendor during the warranty period (Annexure 2, clause 5). Report it in writing and attach a few months of your log.
If a PM Surya Ghar vendor does not respond, you can raise a grievance through the National Portal, the Portal app or the National Call Centre. Each grievance gets a unique tracking ID, updates come by SMS, email and other channels, and the guidelines say grievances will be resolved within 30 days (Section 11). Meter faults are a KSEB matter: KSERC makes the distribution licensee responsible for the testing, installation and maintenance of the metering equipment and its adherence to applicable standards (Regulation 15.5).
Cleaning and servicing steps are covered in more detail in our solar panel maintenance guide.
Check this against your bill
FGE Solar can review your latest KSEB bill and tell you which system size is worth pricing.
Frequently Asked Questions
How many units should a 1 kW solar plant make in a day in Kerala?
No official figure is fixed for an individual roof. For storage planning, KSERC reckons generation potential at a 19% capacity utilisation factor (Regulation 16.9). As an example, that is about 4.6 units per kW a day averaged over a year, with lower days in the monsoon.
Where does my KSEB bill show what my plant produced?
Look for the renewable generation line. Regulation 28.3(i) requires each prosumer bill to show the units recorded on the RG meter during the billing period, with opening and closing readings. Subtract the opening reading from the closing reading to check the figure yourself.
Is it normal for solar output to fall a little every year?
Yes, within limits. MNRE's PM Surya Ghar specifications require module degradation below 0.5% per annum, with output above 90% of nominal in the first 10 years and above 80% in the next 15. A sharp drop is a fault to report, not normal ageing.
Who pays to fix an under-performing PM Surya Ghar plant?
The registered vendor, during the 5-year CMC period from commissioning. Section 7(d) of MNRE's guidelines says non-performing or under-performing components are to be repaired or replaced free of cost in that period. Keep your agreement, warranty cards and readings ready when you call.
Should I climb up and clean the panels when output drops?
No. Check the weather, shade and the inverter display from the ground first. If cleaning is needed, follow the method in your manual or ask the installer to do it. Never step onto a wet or sloping roof.
Official Sources and Accuracy Note
- 01KSERC (Renewable Energy and Related Matters) Regulations, 2025 (gazette PDF)
RG meter definition and bill generation line, 19% CUF planning yardstick, and licensee duty to maintain metering equipment (Reg 3(82), 3(73), 15.5, 16.9, 28.2, 28.3).
govt source · opened 2026-10-16 - 02MNRE Guidelines for PM-Surya Ghar: Muft Bijli Yojana (CFA to Residential Consumers)
Module output floors and degradation, 75% performance ratio, 5-year CMC, inverter data link and grievance route (Annexures 2 and 3; Sections 7 and 11).
govt source · opened 2026-10-16
Accuracy note: This guide is built from government pages, regulator orders, and news sources on the web. Rules and amounts change. Some details may be outdated or wrong. Check the official links below before you pay, apply, or complain to KSEB.