An electricity bill that jumps out of nowhere is stressful — but in most cases the explanation is boring rather than sinister. A longer billing cycle, a wrong tariff category, a settled estimate, carried-over arrears, or a slab boundary crossed can each raise the total without a single additional unit of consumption. Genuine meter faults exist, but they are near the bottom of the list.
This checklist walks you through the ten real reasons a bill increases, in the exact order you should investigate them. Start with the units-per-day test, work through the list, and you will almost always find the culprit on paper before anyone needs to check your meter.
Start With Units Per Day
Ignore the rupee figure and check the arithmetic first. Divide the billed units by the number of days shown on the bill, then compare with your average from the last 6–12 bills. If units per day is unchanged, your consumption did not rise — something about the billing did. If units per day genuinely doubled, read on for reasons 6, 7, and 10.
This single test filters out most false alarms. A 45-day bill with 375 units looks scary next to a 30-day 250-unit bill, until you notice both are 8.3 units per day. The calendar, not your usage, did the damage.
The 10-Reason Checklist
1. The billing period is longer than 30 days
Cycles of 40–45 days are common, especially after a changeover, a festival, or a delayed reading. Check the "number of days" field first. A longer period legitimately carries more units — and in bi-monthly states, a single bill can cover 60 days. See our guide to bi-monthly billing for the larger version of this trap.
2. Wrong tariff category
If your connection is billed under Commercial instead of Domestic, every unit is priced higher. This silent inflator is easy to miss because the category sits in small print near the tariff table. Compare the category on your bill with your contract; if it is wrong, the discom should revise and refund the difference for the affected period.
3. An estimated reading got corrected
If previous months were billed on estimates and the actual reading finally arrived, the difference lands in this bill as a catch-up charge. It is not new consumption — it is months of unpaid difference settled at once. The mechanism is the same one that produces smart-meter catch-up bills.
4. Arrears carried forward
Unpaid previous bills, plus interest, get loaded onto the current bill. Look for an "arrears", "outstanding", or "dues" line. If you paid everything, a swapped-in arrears figure is a billing error worth disputing.
5. Slab crossing (the threshold effect)
Passing the 200, 300, or 400-unit boundary re-prices the units beyond it at a higher rate. Even with identical daily usage, crossing one boundary in a hot month can jump the bill by hundreds of rupees. The BijliCalculator bill calculator shows the boundary effect per slab.
6. A new or older heavy appliance
Air conditioners and geysers typically make up 40–60% of summer bills. An AC installed before the last bill, a second fridge, or a geyser left running adds hundreds of units a month. Count appliances added since your last reasonable bill.
7. Standby and phantom loads
Devices left on standby 24×7 — TVs, set-top boxes, routers, chargers — draw a constant trickle. A few watts each is invisible until you add it up: roughly 15 such loads at 5 watts each run about 5 units a month. Phrase it differently: 24×7 standby from any set of devices adds units without anyone noticing.
8. FAC / FPPCA spikes
Fuel and power purchase adjustments climb when fuel prices rise or purchases shift, adding ₹100–200 in a bad quarter. The amount appears as a line item on the bill. Compare this line with older bills; it swings independently of your usage.
9. Duty changes or new levies
State governments occasionally raise electricity duty or add a new levy, which changes the total even with identical units. A one-line duty-rate change on the tariff page explains a uniform increase across many customers at once.
10. Meter issues — fast meter, reading error, or interchange
Only after checking all nine reasons above should you suspect the meter. A fast meter, a mis-typed reading, an interchanged neighbour's reading, or smart-meter catch-up can all inflate a bill. This is when the 5-minute meter check earns its keep.
The Honest Tenth Entry: A Hot Summer
There is one more cause that needs no error at all: the weather. In June 2026, MSEDCL reported consumption rising 22–28% across all meter categories compared with June 2025. Millions of households used genuinely more power last summer. A hot month raises AC run-hours, fan speeds, and fridge workload at once — and when it crosses a slab boundary on top of that, a perplexing bill is simply the honest price of the heat.
Check your bill against the same month last year, not the month before. June versus May hides the seasonal jump; June versus June shows it plainly. If your units per day rose but your neighbours report the same, the heat is the explanation — and the slab effect is the amplifier.
| Reason | How to check | Likely outcome |
|---|---|---|
| Longer billing period | Read the "number of days" field | Legitimate — divide units by days |
| Wrong category | Check Domestic vs Commercial on bill | Correction plus refund of difference |
| Estimate corrected | Look for a difference line vs old estimates | Legitimate — one-time catch-up |
| Arrears | Look for an outstanding/dues line | Dispute if you actually paid |
| Slab crossing | Check which slabs the units were priced in | Legitimate — threshold effect |
| New appliance | Count units per day vs added appliances | Legitimate usage increase |
| Standby loads | Inventory 24×7 plugged-in devices | Fixable — unplug or switch off |
| FAC spike | Compare FAC line across bills | Legitimate — outside your control |
| Duty / new levy | Check tariff page for rate changes | Legitimate — affects all customers |
| Meter issue | Read meter, photograph, test under regs | Test, revise, refund if confirmed |
Investigate in This Order
The nine-part procedure stops most cases from even reaching a meter. Take your bill and walk it one reason at a time: check the days covered, confirm the category, compare units per day with six bills of history, hunt for arrears or adjustment lines, count new appliances, and compare this FAC line with older bills. Only if everything else checks out — and the units per day align with no new equipment or long period — do you ask the discom to look at the meter.
Two bills in your hand are worth more than a month of calls. Spread the last six bills on a table and circle the units, the days, and the FAC line in each. The pattern answers most questions itself: a gradual climb suggests appliances or seasons, while a single sudden spike points to a specific event — a delayed cycle, a corrected estimate, or an error.
When the Bill Is Genuinely Wrong: The Escape Ladder
- Photograph your meter with the date visible in the frame.
- Register a complaint with the discom's portal or by phone, and note the complaint number.
- Ask for a re-reading or verification within the discom's response time.
- If the dispute persists, escalate to the CGRF, then the Electricity Ombudsman.
The same ladder applies whether the problem is a reading or a category. Reference the ten reasons in your complaint — a checklist complaint is answered faster than a vague one, and the paper trail decides the case.
Keep every document from day one: the disputed bill, your meter photograph, the complaint number, and the discom's replies. Most disputes are decided on paper, and the side with the complete folder almost always wins. A five-minute check today can save a full refund chase tomorrow.
FAQs
Why did my electricity bill double in one month?
Usually because the bill covers more than 30 days, or because it includes a catch-up for previously estimated readings, arrears, or a larger FAC. Compare units per day, not the rupee figure, and check the "days" and "arrears" lines before worrying.
Can a slab boundary make my bill jump without more usage?
Yes. Domestic tariffs price units in rising slabs. When your total passes the 200, 300, or 400-unit boundary, all units beyond it are priced at the higher rate. One extra hour of AC can push you over a boundary and raise the whole bill.
How do I check if my bill is for the wrong category?
Find the tariff category printed on the bill and compare it with your connection's contract. Domestic rates apply to residences; a commercial classification charges more per unit. If wrong, complain and ask for the difference to be refunded for the affected period.
What is FAC and why is it on my bill?
Fuel Adjustment Charge (also FPPCA in some states) recovers movement in fuel prices from consumers. It changes every cycle and can add ₹100–200 in a bad quarter. It is independent of your usage — compare the FAC line across your bills.
My units per day genuinely doubled. What now?
Count new or heavy appliances, check standby devices, and verify the month against the same month last year — summers raise usage sharply. If none explain it, suspect the meter and run the 5-minute check, then ask the discom for testing.
Can I complain even after paying?
Yes. Paying does not waive the right to dispute an incorrect bill. Hold the meter photograph, file a complaint with your receipt number, and pursue re-billing through the CGRF and Ombudsman if needed.
