Net Metering Banking: How Your Bill Is Actually Calculated

Your customer calls you two months after commissioning. "Bhai, my bill is not zero. You said solar means zero bill." You open the bill, and there it is: 214 units imported, 168 units exported, and a payable amount nobody explained to the customer. This is the single most common after-sales dispute for Indian rooftop EPCs, and it happens because nobody sat the customer down and explained how the meter actually talks to the bill.

This post is the explanation you can send to every customer, and the math your sales team should put inside every proposal. If you need the basics first, read our explainer on what net metering is and how the bidirectional meter records both directions of flow.

Every number in this post uses published tariff orders and regulations. Where rules differ by state, we say so. Where we run an example, we label it as an example.

Import, export and net units: the three numbers on the bill

Your bill is built from exactly three meter readings: import units (grid to home), export units (solar to grid), and the net of the two. The net metering meter, called a bidirectional or net meter, records import and export in separate registers. Your DISCOM (Distribution Company) bills you on the net figure, not on gross consumption.

Here is the part most customers never hear. Solar self-consumption never appears on the bill at all. If your 3 kW system generates 360 units in a month and your home uses 200 of those directly while the sun shines, the meter never sees those 200 units. They are free in the purest sense. Only the surplus, the 160 units that flowed out to the grid, shows up as export.

So the monthly math is: billable units = import minus export. If you imported 214 and exported 168, you pay for 46 units at your slab tariff, plus fixed charges. That is the 46-unit bill your customer did not expect.

What banking of surplus units actually means

Banking is a credit ledger, not a savings account with interest. When your export exceeds your import in a billing month, the surplus units are "banked" with the DISCOM and carried forward to the next bill. Next month, if you import more than you export, the banked units are drawn down to reduce what you pay.

Think of it like a prepaid balance measured in units, not rupees. A home that exports 120 extra units in February carries 120 units forward. If March sees 80 more imported than exported, 80 banked units are consumed, and 40 stay in the ledger.

Two rules make or break the value of banking. First, banked units are valued in energy terms (kWh), so a unit banked in a cheap month offsets a unit in an expensive month at par. That works in the customer's favour. Second, whatever is left in the ledger at the end of the settlement year gets converted to cash at APPC, which is where the value collapses. We will come to APPC shortly.

Settlement cycles and APPC: when banked units become money

The settlement cycle is the period after which the DISCOM closes the banking ledger and pays out or lapses what remains. In most states the cycle is the financial year, closing on 31 March. Some states settle monthly. The rules come from the State Electricity Regulatory Commission (SERC), not the DISCOM, as explained in the state-by-state DISCOM net metering process guide by Heaven Designs.

APPC stands for Average Power Purchase Cost. It is the average price the DISCOM paid to buy power from generators in the previous year, excluding renewable and short-term purchases in most definitions. Each SERC publishes its APPC figure in tariff orders. Current working numbers installers quote in 2026: roughly ₹2.85 per unit for Gujarat DISCOMs, ₹3.00 in Andhra Pradesh (APERC 2024 tariff order), ₹3.20 in Telangana (TSERC tariff order 2024-25), and ₹3.35 in Rajasthan (RERC 2024 tariff order), per Heaven Green Energy's DISCOM process guides, 2026.

The tradeoff is real and worth stating plainly. Banking protects the customer from paying retail in low-generation months, which is genuinely useful through monsoon. But every unit still sitting in the ledger on 31 March gets converted at APPC, roughly one-third of retail value. An oversized system that banks 1,500 units a year is gifting the DISCOM cheap power. Sizing to actual consumption beats oversizing for export.

Billing math with real tariff numbers

Now for two worked examples. These are hypothetical examples using real published tariff slabs, labelled so your team can redo the math with your own DISCOM's numbers.

Example 1, Surat (DGVCL), 3 kW residential, a normal month. The home consumes 380 units total. Solar generates 360 units, of which 150 are self-consumed and 210 exported. Import from grid is 230 units (380 minus 150 self-consumed). Billable units = 230 import minus 210 export = 20 units. Under DGVCL domestic slabs, energy charges on 20 units sit in the lowest slab around ₹3.05 per unit (GERC tariff order FY2024-25), so the energy charge is about ₹61, plus fixed and meter charges. Without solar, 380 units would have cost roughly ₹1,900 in energy charges. The customer saves over ₹1,800 that month, but not the "zero bill" an oversold pitch promised.

Example 2, Pune (MSEDCL), 5 kW residential, the annual settlement. Across the year the home banks a net 900 surplus units by 31 March because the family was away for three months. At an APPC near ₹3 per unit, the year-end credit is roughly ₹2,700. Had those 900 units been self-consumed at MSEDCL's upper residential slabs (around ₹9 to ₹12 per unit under the MERC tariff order FY2025-26), they would have been worth ₹8,000 or more. Same electrons, one-third the value. That is the banking tradeoff in one number.

If you want this math rendered automatically inside your quotes, our guide on showing ROI in a solar proposal covers the exact fields to include.

The Meter Ledger Method: a 4-step way to explain any bill

We use a simple proprietary frame at QuickEstimate called the Meter Ledger Method. It turns any confusing net metering bill into four lines a customer can verify themselves. Teach it to every sales rep.

1. 1

   Read import and export from the bill

   Find the two registers the DISCOM prints: import (grid to home) and export (solar to grid). These are the only two raw numbers that matter.

2. 2

   Compute the net for the month

   Net = import minus export. Positive means you pay for the difference at slab tariff. Negative means the surplus is banked and carried forward.

3. 3

   Track the banked balance across months

   Keep a running ledger: opening banked units plus this month's surplus, minus this month's drawdown. The balance is what rides into the settlement date.

4. 4

   Apply the settlement rule at year end

   On 31 March (in most states), multiply remaining banked units by your DISCOM's APPC. That credit, not retail tariff, is what an oversized system actually earns.

Run this four-line ledger with the customer at proposal time, using their last 12 months of bills. It takes ten minutes and kills the "zero bill" objection before it is born.

Net metering vs gross metering

Under gross metering, every unit your solar generates is exported and bought by the DISCOM at a feed-in tariff, while you buy 100% of your consumption at retail. Under net metering, you self-consume first and only the surplus is exported. Our full comparison lives at net metering vs gross metering, and the gross metering glossary entry defines the term.

State variations you must check before quoting

Banking rules are SERC territory. The same 3 kW system behaves differently on paper in Surat than in Jaipur. This table is a working summary; always confirm against the current SERC order, and our net metering DISCOM list and net metering charges guide carry the per-state application detail.

What most installers get wrong

Here is our opinionated take, held firmly: the industry misconception that "a bigger system means a bigger saving" is wrong under net metering banking, and installers who sell oversized systems to inflate ticket size are quietly destroying their customers' returns. Every exported unit that never gets drawn down is worth ₹3, not ₹8. A 5 kW system on a home that needs 3 kW is not generosity. It is bad engineering.

The "what most installers get wrong" moment we see constantly: reps quote savings as generation multiplied by retail tariff. That assumes 100% self-consumption, which almost no home achieves. Typical residential self-consumption without batteries runs 30% to 60% depending on daytime occupancy. A Rohini family (hypothetical example) with a 3 kW system and everyone at office or school till 6 pm will export half their generation. Their honest annual saving is closer to ₹22,000 than the ₹32,000 a lazy proposal showed. When the real bill arrives, the customer blames you, not the math.

The fix is boring and it works: pull 12 months of bills, model self-consumption honestly, size to consumption, and show the APPC line for the surplus. State-wise payback differences are covered in our solar payback period by state analysis, and the subsidy side of the math is in the PM Surya Ghar subsidy slabs post (₹78,000 central grant for 3 kW and above, per the PM Surya Ghar National Portal, 2026, and MNRE).

How QuickEstimate fits

Explaining banking math customer by customer does not scale past five site visits a day. QuickEstimate builds the consumption-based savings estimate, the subsidy deduction, and the honest payback line directly into the proposal your rep sends from the field, so the "zero bill" myth never enters the conversation and the first bill never becomes a dispute call.

• Proposal Generator, 60-second branded PDF with system size, PM Surya Ghar subsidy and savings math pre-filled from the customer's bill data.
• Quotation System, standardised pricing and payback assumptions across your whole team, no rep inventing his own tariff math.
• WhatsApp Follow-up, send the proposal and a banking explainer to the customer's WhatsApp and track when they read it.
• Sales Reports, see which reps oversize systems and which close honest, consumption-matched deals.

What to do this week

Three concrete actions for your EPC in the next seven days.

1. Pull the APPC figure for every DISCOM you operate in from the latest SERC tariff order, and pin it in your team's WhatsApp group.
2. Rewrite your proposal template's savings section to show import, export, banked units and the APPC settlement line separately. Kill any line that promises "zero bill".
3. Teach your reps the Meter Ledger Method on one live customer bill this week. Ten minutes per bill, and the after-sales dispute calls drop.

If you want the math automated instead of memorised, book a demo and we will walk you through a live proposal with your own DISCOM's numbers.

Frequently asked questions

What is net metering banking in simple terms?

Net metering banking is a unit ledger with your DISCOM. When your solar system exports more than you import in a billing month, the surplus units are credited and carried forward to offset future bills. Whatever remains unadjusted at the end of the settlement period, usually 31 March, is paid out at the Average Power Purchase Cost, roughly ₹3 per unit in most states.

How is my net metering bill calculated each month?

Your billable units equal imported units minus exported units for that month. If the result is positive, you pay for the difference at your slab tariff plus fixed charges. If negative, the surplus is banked. Energy you self-consume from solar never appears on the bill at all, which is why daytime usage is the most valuable.

What is APPC and who decides it?

APPC is the Average Power Purchase Cost, the average price your DISCOM paid generators for power in the previous year. Each State Electricity Regulatory Commission publishes it in tariff orders. Working figures in 2026 range from roughly ₹2.85 per unit in Gujarat to ₹3.35 in Rajasthan, well below residential retail tariffs.

Do banked units expire?

In most states, banked units do not expire during the financial year but lose value at settlement. On the settlement date, typically 31 March, remaining units are converted to a monetary credit at APPC rather than carried as units. Some states lapse or devalue them instead, so check your SERC's current net metering regulations.

Is net metering better than gross metering for homes?

For almost every Indian home, yes. Net metering lets self-consumed units offset retail tariff worth ₹4 to ₹12 per unit, while gross metering sells all generation at a feed-in tariff near ₹3 to ₹4 and you buy everything back at retail. Gross metering suits generation-first investors or where the SERC mandates it above a threshold.

What is the maximum system size allowed under net metering?

Under the Ministry of Power's Electricity (Rights of Consumers) Amendment Rules 2021, net metering is permitted up to 500 kW or your sanctioned load, whichever is lower. Individual SERCs can set tighter caps, and several states apply lower limits for specific consumer categories, so confirm with your DISCOM before sizing.

Why is my bill not zero after installing solar?

Because you still import units at night and on cloudy days, and those imports are only partly offset by your exports. Fixed charges and meter charges also continue regardless of generation. A correctly sized 3 kW system on a 380-unit monthly consumption typically cuts the energy charge by 90% or more, but rarely to an absolute zero.