Is your solar system underperforming? Check in 10 minutes.

Installed does not mean working well.

A rooftop system can run for months with a loose connector, a failed string or heavy soiling, and nothing will look wrong. The lights stay on and the BESCOM bill still arrives. You only notice if you compare what the system produces against what it should. That comparison takes about ten minutes once a month.

Step 1: Know your daily number.

Your inverter or its app shows generation in kWh. Look at two figures: today's total and the lifetime total. Write down the lifetime figure on the first of each month. The difference between two readings, divided by the days in between, is your average daily generation.

Step 2: Compare it with a realistic range.

As a rough rule of thumb, a well-sited system in Bengaluru often produces around 3.5 to 4.5 kWh per day for every 1 kW installed on a clear day. Treat this as an estimate, not a guarantee. Your actual range depends on tilt, orientation, shading and season. For a 3 kW system, that would suggest roughly 10 to 13 kWh on a bright day.

Ask your installer to write down the expected monthly generation for your specific roof in the quote or handover document. That figure, not a generic rule, is your benchmark. If you have not seen one, ask for it. Our guide on monsoon generation explains why June to September will always sit lower, so compare like months with like months.

Step 3: Check a clear midday reading.

Between 11 am and 1 pm on a cloud-free day, look at the inverter's live power in kW. A healthy system will usually show a figure somewhat below its rated capacity, because panels rarely hit their label value in real conditions. If a 3 kW system peaks at 1 kW on a clear noon, something is wrong. Photograph the display and share it with your installer.

Step 4: Read the inverter for faults.

Most inverters show a status light or a screen. Green or "normal" is what you want. A steady red light, an error code or a message about grid voltage or isolation means the system is either off or running in a reduced state. Note the code. Do not open the inverter or touch the DC wiring yourself. Send the code and a photo to your installer and ask for a response time in writing.

Step 5: Look at the panels, from a safe place.

You do not need to climb up. From a terrace edge or a neighbouring building, look for visible dust, bird droppings, leaves, or a new shadow from a tree, tank or construction. Soiling and shading are the most common causes of a drop that has no electrical fault. Our cleaning guide and shading guide explain what to do about each.

Step 6: Cross-check against your BESCOM bill.

Your net meter records imports and exports separately. Compare the exported units on the bill with what the inverter says you generated, keeping in mind that you use some of the output at home before anything is exported. The two will not match, but they should move together. If generation looks normal on the app and exports fall sharply while your usage is unchanged, ask whether the net meter reading or the inverter's own meter could be at fault. Our export credit guide shows how those units are settled.

When to call your installer.

Call if output is persistently well below your written benchmark for comparable days, if the inverter shows a fault, or if the monitoring app has stopped reporting. A gap of a few days is often just weather or a Wi-Fi drop. A gap of weeks needs a site visit. Check your warranty terms first: our inverter warranty guide covers what is usually included.

Keep a simple log.

Note the date, lifetime kWh, weather and anything unusual. After three months you will know your system's normal, and a real problem will stand out quickly. It also gives you a clean record if you ever need to raise a warranty claim or sell the property.