How to Read Your Electricity Bill Before Going Solar
Read your electricity bill like a solar engineer: units, slabs, fixed charges, FAC/FPPAS, duty, sanctioned load, and net-metering lines after solar.
Short answer: for solar, five lines on your bill matter: units consumed (to size the system), tariff slabs (to value each saved unit), per-unit add-ons like wheeling, FAC/FPPAS and duty (solar saves these too), fixed charges (solar does not remove them), and sanctioned load and phase (to check what size you are allowed). After solar, look for import, export and banked units on the net-metered bill.
The anatomy of a typical bill
| Line | What it means | Does solar reduce it? |
|---|---|---|
| Consumer number | Your account ID; needed for PM Surya Ghar | n/a |
| Tariff category | e.g. LT-I residential, LMV-1 domestic | n/a |
| Sanctioned / connected load | Approved kW or kVA | n/a, but caps solar size |
| Phase | Single or three phase | n/a |
| Previous and current reading | Meter readings; difference = units | yes |
| Units consumed | kWh used this cycle | yes |
| Energy charges | Units × slab rates | yes, most |
| Wheeling charge | Per-unit network charge (e.g. MSEDCL) | yes |
| Fixed / demand charge | Monthly fixed amount, sometimes per kW | no |
| FAC / FPPAS / FPPCA | Per-unit fuel and power cost adjustment | yes |
| Electricity duty / tax | % of bill or per unit | mostly yes |
| Meter rent | Monthly | no |
| Subsidy / free units | State scheme credits | can shrink savings |
Line names vary: MSEDCL prints "Wheeling charge" and "Fuel adjustment charge (FAC)", Gujarat DISCOMs print "FPPPA charges", BESCOM prints "P&G surcharge" and "Tax", UP prints "FPPAS".
Slabs: why the last unit is the expensive one
Most states use telescopic slabs: the first block of units is cheap, later blocks cost more. Solar removes your most expensive units first.
Example, MSEDCL residential (FY 2026-27, verify on your bill):
| Slab (units/month) | Energy rate | Wheeling | Effective before duty |
|---|---|---|---|
| 0–100 | ₹3.96 | ₹1.60 | ₹5.56 |
| 101–300 | ₹10.80 | ₹1.60 | ₹12.40 |
| 301–500 | ₹15.03 | ₹1.60 | ₹16.63 |
| above 500 | ₹17.53 | ₹1.60 | ₹19.13 |
Add 16% electricity duty on the whole bill. A home at 300 units that saves 200 units a month with solar removes units from the 101–300 slab, worth about ₹14.4 each with duty, more than the bill's average of about ₹11.7 per unit.
Some states are different: - Karnataka: one flat energy rate (₹5.80) for all units. - Kerala: above 250 units a month, all units are charged at a higher non-telescopic rate, so crossing 250 is costly. - Tamil Nadu: slabs are bi-monthly, and up to 200 units per cycle may be free for eligible homes. - Telangana: the slab set depends on total units; going above 200 moves you to a higher set.
Per-unit add-ons are savings too
FAC/FPPAS changes often. In Gujarat it can be about ₹2.5–3 per unit and often dominates the bill. In UP the FPPAS was 10% in June 2026. Because these are charged per unit, every unit of solar avoids them. Read the latest bill for the current value.
Fixed charges stay
Fixed or demand charges are based on your connection, not usage. Solar does not reduce them. Some states charge fixed costs per kW of sanctioned load (Karnataka ₹150 per kW, UP urban ₹110 per kW), so increasing sanctioned load for solar can raise them slightly.
Sanctioned load and phase
- Most DISCOMs cap rooftop solar at your sanctioned load.
- Up to 10 kW can be single- or three-phase; above 10 kW must be three-phase.
- Some DISCOMs cap single-phase inverters on three-phase connections at around 5 kW.
If the load is too low, apply for enhancement along with the solar application.
Free-unit and subsidy schemes
Look for lines such as "Gruha Jyothi", "Govt subsidy" or "free units". If your state pays for your first 100–200 units, solar only saves the units above that. Size for what you pay, not what you use.
After solar: the net-metered bill
Expect new fields:
- Import units (from grid) and export units (to grid)
- Net units billed
- Banked / carried-forward units from earlier months
- Generation units, if a generation meter is installed
- Surplus credit or payment at settlement
- In Maharashtra above 10 kW, a grid support charge on gross generation
If the export reading stays at zero on sunny days, the net meter may be installed incorrectly; call the installer.
Turn your bill into a solar size
- Add 12 months of units and divide by 12.
- Divide yearly units by your city yield (about 1,400–1,650).
- Check sanctioned load and roof space.
Then read solar for 200 units, 300 units or 500 units, and payback and IRR.
What to send your installer
A good installer can size and price from:
- The latest bill (both sides), plus the units from the last 12 months (many DISCOM apps show this history)
- Sanctioned load and phase
- Whether anyone in the home plans an EV, AC or induction cooktop soon
- Two roof photos, morning and afternoon
That is enough for an honest first estimate before a site visit.
Red flags on a net-metered bill
- Export stays at zero on sunny months
- Banked units disappear without a settlement line
- Billing switched to "average" or "faulty meter" readings
Raise these with the DISCOM promptly and keep copies of meter photos.
Talk to Sunlectric
Confused by a line on your bill? WhatsApp a photo to +91 89567 89307 (wa.me/918956789307) and our Solar Desk will tell you your slab, the value of a saved unit and a sensible system size. Installers can enter bill lines directly in Sunlectric Studio to get a state-accurate proposal.
Sources
- MSEDCL tariff FY 2026-27: MSEDCL tariff details; MERC order Case 75 of 2025 (secondary-source rates, verify)
- Gujarat tariff schedule from 1 Apr 2026: GERC
- UP FPPAS June 2026: Business Today, 30 May 2026
- Karnataka tariff: KERC tariff order 2025
- KSEB tariff 2025–27: KSEB circular
- Tamil Nadu tariff and free units: TNERC; The DISCOM Bill, Jul 2026
- Telangana tariff: TGSPDCL tariff file
Questions people ask
Which number on my bill decides the solar size?
Units consumed (kWh) per month, averaged over 12 months. Divide the yearly total by your city's yield of about 1,400–1,650 units per kW per year.
What is sanctioned load and why does it matter for solar?
It is the maximum load your connection is approved for, in kW or kVA. Most DISCOMs allow rooftop solar up to the sanctioned load, so a 2 kW sanction usually limits you to 2 kW unless you apply for enhancement.
What is FAC or FPPAS on my bill?
A fuel and power purchase cost adjustment that DISCOMs add per unit, revised often (monthly in many states). In Gujarat it can add ₹2–3 per unit. Because it is per unit, solar saves it too.
Why is my bill not zero after installing solar?
Fixed charges, meter rent and some taxes remain, and monthly settlement or low surplus rates mean exported units are worth less than imported ones.