Import vs Export Units in Net Metering: Your Bill Explained

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 a 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.

Where a rule below comes from a regulation, we name it and its date. Where we run an example, the numbers are assumptions and we label them. We could not verify current APPC figures, so we do not quote any.

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 period is settled under your state's rule, which is where the value can collapse: some states pay a notified rate, and West Bengal's 2025 rules reset leftover units to zero, as our WBSEDCL net metering guide explains. We will come to settlement rates 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 West Bengal the settlement period generally runs from 1 April to 31 March, while Telangana's 2025 regulation settles net exports 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, the average price a DISCOM pays for power. Where a state's rule pays surplus at APPC, the figure comes from that Commission's tariff order, so get it from the latest order for your DISCOM. We could not verify current APPC figures, so we do not quote any. Not every state uses APPC: Telangana's 2025 regulation settles exports above imports at the lowest tariff in solar PPAs the DISCOMs signed in the preceding financial year (notified each year), and West Bengal's net metering resets leftover units to zero. Our partner guide to state-by-state differences is a starting point, not a source for rates.

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 at settlement gets converted at your state's rate, which in some states is a small fraction of retail value and in West Bengal is nothing. An oversized system that banks a large surplus every year is gifting the DISCOM cheap power. Sizing to actual consumption beats oversizing for export.

Billing math with assumed tariff numbers

Now for two worked examples. These are hypothetical, and every rate in them is an assumption, so your team can redo the math with your own DISCOM's current slabs and your state's settlement rule.

Example 1, an illustrative 3 kW home in Surat (DGVCL), 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. Assume the first domestic slab is ₹3.05 per unit, so the energy charge on 20 units is about ₹61, plus fixed and meter charges. Assume an average of ₹5 per unit across slabs, so 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, an illustrative 5 kW home in Pune, the annual settlement. Across the year the home banks a net 900 surplus units by the settlement date because the family was away for three months. Assume a year-end settlement rate of ₹3 per unit (check your state's actual rule; in West Bengal the credit would be zero). The credit is then ₹2,700. Had those 900 units been self-consumed at an assumed ₹9 per unit, they would have been worth ₹8,100. Same electrons, one-third the value under these assumptions. That is the banking tradeoff in one number.

If you want this math 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 Quickest Solar CRM 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 the settlement date your state sets, apply your state's rule to the remaining banked units (a notified rate, or zero in some states). 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 Kolkata. This table is a working summary of regulator texts we opened on 31 October 2026; 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 your state's settlement rate, not the retail rate. 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 few homes achieve without batteries, and the share depends on daytime occupancy. Take an illustrative family in Rohini with a 3 kW system and everyone at office or school till 6 pm, and assume about 4,300 units generated a year, ₹7.50 per unit retail, ₹3 per unit for exported surplus, and half the generation exported. Their saving is about ₹22,600 a year, not the ₹32,000 a lazy proposal showed (4,300 units at ₹7.50). 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 settlement-rule 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 Quickest Solar CRM fits

Explaining banking math customer by customer does not scale past five site visits a day. Quickest Solar CRM lets your rep make an estimate on the mobile app and send a branded proposal PDF with the PM Surya Ghar subsidy applied in the proposal, so you can add your own consumption assumptions and settlement-rule note to the terms and keep the "zero bill" myth out of the conversation.

• Proposal Generator, branded PDF with your logo, items, product photos, terms and conditions, and the PM Surya Ghar subsidy applied in the proposal.
• Quotation System, an admin-set price list with margin, so every rep quotes from the same prices. Agree your tariff and settlement assumptions as a team and put them in the terms.
• WhatsApp Follow-up, share the proposal PDF on WhatsApp and keep a saved message template with a short banking explainer.
• Sales Reports, use the dashboard and team report to review the proposals each rep sends, and check system sizes against customer consumption.

What to do this week

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

1. Find the surplus settlement rule for every DISCOM you operate in from the latest SERC regulation and tariff order (a notified rate, APPC, or zero), 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 settlement-rule line separately. Kill any line that promises "zero bill".
3. Teach your reps the Meter Ledger Method on one live customer bill this week. It takes about ten minutes a bill.

If you want the math automated instead of memorised, book a demo and we will walk you through a live proposal.

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 is settled under your state's rule: a notified rate in some states (Telangana settles monthly at the lowest solar PPA tariff of the previous year), and reset to zero under West Bengal's net metering.

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. We could not verify current figures, so we do not quote any. Not every state uses APPC: Telangana's 2025 regulation uses the lowest solar PPA tariff of the preceding year, and West Bengal's net metering resets leftover units to zero.

Do banked units expire?

It depends on the state. Under West Bengal's 2025 regulation, net exported energy left at the end of the settlement period (generally 31 March) is reset to zero, and the accumulated surplus is reset at the start of each financial year. Telangana settles exports above imports monthly at a notified rate. Check your SERC's current net metering regulation.

Is net metering better than gross metering for homes?

For most Indian homes with daytime consumption, usually yes. Net metering lets self-consumed units offset the retail tariff, while gross metering sells all generation at the feed-in tariff (West Bengal's 2025-26 rates are ₹3.73 to ₹4.37 per kWh) 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?

The State Commission sets it. Where its regulations are silent, the Electricity (Rights of Consumers) Amendment Rules 2021 let the Commission allow net metering up to 500 kW or your sanctioned load, whichever is lower. Examples: West Bengal 500 kW or contract demand or sanctioned load, whichever is lower (2025); Telangana 500 kWp (2025); Maharashtra 5 MW or contract demand or sanctioned load, whichever is lower (2023 amendment). 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. In the worked example above, the energy charge falls from about ₹1,900 to about ₹61, but fixed charges remain and the bill is rarely an absolute zero.