Solar installed, bill still confusing? Read it line by line.

The bill changes the day net metering starts.

For years your BESCOM bill was one number to pay. After rooftop solar with net metering, it becomes a small ledger. Many owners glance at the amount due, see a low figure and assume everything is fine. That misses the point: the bill is the only place where you can check whether your system is really paying you back. This note walks through what to look for. BESCOM's bill layout can change and differs by tariff category, so treat the headings below as things to find on your own bill, not exact labels.

Five things to find on every bill.

• Units imported from the grid. This is what you drew when the panels were not covering the house, mostly evenings, nights and cloudy spells.
• Units exported to the grid. This is the surplus your panels sent out, mostly through the daytime when the house was using less than the panels made.
• Net units, and any carried-forward balance. Under net metering, exported units are set against imported units. If you exported more than you imported, the extra is normally carried forward to the next bill rather than lost. How long it carries and what happens at the end of the settlement period is covered in our note on export credit settlement.
• Fixed or demand charges. These do not go away because you installed solar. Your sanctioned load, not your consumption, drives them. See sanctioned load.
• Other per-unit and tax lines. Surcharges and taxes can be applied on units or on the total in ways that differ from the energy charge. Ask BESCOM or your installer exactly which lines are calculated on net units and which on gross imports. Do not assume.

Why a Rs 0 energy charge is not a Rs 0 bill.

Owners are often surprised to see a payable amount in a month when net units were zero or negative. The usual reason is the fixed charge, plus any per-unit levy that is not netted off. Our note on the true-up charge shows one example of a per-unit item that changes the sums. Your bill will rarely go to zero, and an installer who promises a zero bill is overselling.

A simple monthly check, with illustrative numbers.

These figures are illustrative, not a tariff or a promise. Suppose a 3 kW system generates about 360 units in a month. The house uses 300 units in total. If, say, 200 of those were used while the panels were running, the house drew 100 units from the grid at night, and the panels exported 160 units. On the bill you would expect to see roughly 100 imported, 160 exported, and a net surplus of about 60 units carried forward. If your bill instead shows imports of 250 and exports of 40, something is off, and the cause could be the meter, a shaded or faulty string, an inverter fault, or a wrong reading.

The check to run each month: generation from your inverter app, minus what the house used directly, should roughly equal exports on the bill. Meters and inverters measure at different points, so expect small gaps, not large ones.

Keep a one-page log.

Write down, for each bill, the reading dates, imports, exports, net balance and amount paid. Add the inverter's generation figure for the same period. After six months you will know your own seasonal pattern and can spot a problem early. Monsoon months will look weaker, as explained in our monsoon note, so compare each month with the same month a year earlier once you have one.

When to raise it with BESCOM or your installer.

• Exports show as zero for a month when the panels clearly worked. Ask about the meter configuration and whether it records export.
• Reading dates jump or the bill is clearly estimated rather than read.
• The carried-forward balance disappears without the settlement period ending.
• Generation is far below expectation. Use our 10-minute underperformance check first, then call your installer, who should respond under the warranty and service terms in your agreement.

Keep photos of the meter display on the day of each reading. If there is a dispute, a dated photo is the quickest evidence you can have.

Quick FAQ.

Is a low bill proof that my solar is working? No. A low bill can come from low usage. Compare generation, exports and imports instead of the rupee amount.