How Net Metering Changes Your Electricity Bill
With net metering, your DISCOM bills you only on net consumption: the units you draw from the grid minus the
units your solar system exports. During the day your panels feed the home first, surplus flows to the grid, and
at night you draw back. A system sized close to your consumption can bring the energy portion of your bill to
nearly zero, leaving mostly fixed charges.
Export compensation varies by DISCOM. Some credit exported units one-for-one against imports, others pay a
lower feed-in rate for the surplus. This calculator uses a conservative ₹3.00 per exported unit so your
estimate stays on the safe side.
Example: 3kW Solar System on a ₹3,000 Monthly Bill
A home paying ₹3,000 a month at ₹8.5 per unit consumes roughly 350 units. A 3 kW system in a city with 4.8
peak sun hours generates about 345 units a month, offsetting almost all consumption. The new bill is typically
₹200 to ₹500, mostly fixed charges, which is a saving of around ₹2,500 to ₹2,800 every month. Check your exact
savings and payback with the solar savings and payback
calculator.
Know Your Billing Structure Before You Estimate
Your post-solar bill depends on how your DISCOM bills, not just on how much you generate:
- Slab tariffs cut both ways. Solar removes your most expensive units first: the ones in
the top slab. A home billed across three slabs saves more per unit than its average tariff suggests.
- Fixed charges stay. ₹50 to ₹200 a month of fixed and meter charges survive even a
zero-consumption month; no rooftop system removes them.
- Net metering vs gross rules vary. Most states net imports against exports monthly and
settle surplus annually at a lower rate; a few use different windows. Your sanctioned net-metering capacity
also caps how much export is even counted.
Worked Example: Hyderabad Home, ₹3,500 Bill, 4kW System
A Hyderabad household paying ₹3,500 consumes about 467 units at the ₹7.5 planning tariff. A 4 kW system in
the city's 5.0 sun hours generates roughly 480 units a month, covering the full consumption with a small
surplus worth about ₹40 in export credit. The energy portion of the bill drops to effectively
zero, leaving only fixed charges of ₹100 to ₹200 on the actual DISCOM bill. Monthly saving:
about ₹2,900 to ₹3,400, tracked against the estimate in the
savings calculator.
Reading Your First Post-Solar Bill
The first bill after net metering confuses almost everyone. Check these lines:
- Import and export readings: the bidirectional meter reports both; billing applies to the
net figure.
- Banked or carried-forward units: surplus that rolls to next month appears as a credit
balance, not a payment.
- Settlement month: once a year (often financial year end) accumulated surplus is paid out
or lapses at the DISCOM's notified rate. Note which month yours is.
- Fixed and regulatory charges: unchanged by solar; if the energy charge is near zero, the
bill you still receive is these.
If the first two bills look wrong (for example export units missing), raise it immediately; meter
configuration errors at commissioning are common and fixable.
Bill Estimation Mistakes to Avoid
- Expecting a literal ₹0 bill. Fixed charges and monsoon imports keep a small bill alive in
most months.
- Oversizing for export income. At ₹3 or so per surplus unit, exporting is a poor
investment; size near your consumption instead with the
system size calculator.
- Ignoring sanctioned load limits. DISCOMs generally cap net-metering capacity around your
sanctioned load; a 5 kW system on a 3 kW sanction needs a load extension first.
- Judging by a monsoon bill. July and August import more grid power by design; the annual
picture is what the system was sized for.
How This Solar Bill Calculator Works
Monthly units = Current bill ÷ City tariff (slab-aware where verified)
Residual units = max(0, Monthly units − Solar generation)
New bill = Residual units × Tariff − Exported units × ₹3.00
Assumptions
- Tariffs: city planning tariffs; verified DISCOM slab rules used where available
- Export rate: conservative ₹3.00/unit planning proxy; actual net metering policy varies
- Fixed charges: a small monthly fixed charge usually remains even at zero net units
- Generation: city peak sun hours × 0.8 performance ratio, annualised monthly average
