March 28, 20265 min read

How to Calculate Electricity Bill — Units, Tariff, Slab Rates

Step-by-step guide to calculating your electricity bill from meter readings — units consumed, slab rates, fixed charges, and tips to reduce your bill.

electricity bill units tariff utility calchub household

Your electricity bill isn't just "units consumed × rate." It includes slab-based pricing, fixed charges, fuel adjustment charges, and various duties. Understanding the breakdown helps you verify your bill, estimate future costs, and find ways to reduce consumption.

Here's how to calculate your electricity bill step by step. The CalcHub electricity bill calculator handles slab calculations automatically.

Step 1: Calculate Units Consumed

Units (kWh) = Current Meter Reading - Previous Meter Reading

Example:

Previous reading: 45,230 kWh
Current reading: 45,530 kWh
Units consumed: 45,530 - 45,230 = 300 units (kWh)

One unit = 1 kilowatt-hour = using a 1,000-watt appliance for 1 hour.

Step 2: Understand Slab-Based Pricing

Most Indian electricity boards use slab rates — you pay different rates for different consumption levels. Here's a typical domestic tariff structure (rates vary by state):

Consumption Slab	Rate per Unit
0-100 units	Rs 3.00
101-200 units	Rs 4.50
201-300 units	Rs 6.50
301-400 units	Rs 8.00
401-500 units	Rs 9.00
Above 500 units	Rs 10.00

Important: Slab rates are cumulative in most states. If you consume 300 units, you pay Rs 3.00 for the first 100, Rs 4.50 for the next 100, and Rs 6.50 for the last 100.

Step 3: Calculate Energy Charges

For 300 units with the above slabs:

First 100 units:  100 × Rs 3.00 = Rs 300
Next 100 units:   100 × Rs 4.50 = Rs 450
Last 100 units:   100 × Rs 6.50 = Rs 650
                                   --------
Total energy charge:               Rs 1,400

Step 4: Add Fixed Charges

Fixed charges are a flat monthly fee based on your connection type and sanctioned load:

Connection Type	Typical Fixed Charge
Single phase (up to 5 kW)	Rs 40-80/month
Three phase (above 5 kW)	Rs 120-200/month

For our example: Fixed charge = Rs 60

Step 5: Add Other Charges

Charge	Typical Amount
Fuel Adjustment Charge (FAC)	Rs 0.10-0.50/unit
Electricity Duty	5-16% of energy charge
Wheeling charges	Varies
Meter rent	Rs 15-25/month

Complete Bill Calculation:

Energy charges:          Rs 1,400
Fixed charges:           Rs    60
Fuel adjustment (Rs 0.20 × 300): Rs    60
Electricity duty (10%):  Rs   140
Meter rent:              Rs    20
                         ---------
Total bill:              Rs 1,680

How to Estimate Monthly Consumption

Calculate consumption from your appliances:

Daily units = (Watts × Hours used per day) / 1,000
Monthly units = Daily units × 30

Appliance	Wattage	Hours/Day	Monthly Units
Ceiling fan	75W	12	27
LED bulb (9W)	9W	8	2.2
Refrigerator	150W	24 (auto)	45
Air conditioner (1.5T)	1,500W	8	360
Washing machine	500W	1	15
TV (LED 42")	80W	6	14.4
Water heater (geyser)	2,000W	0.5	30

An AC alone can push your bill from the Rs 3-4.50/unit slab into the Rs 8-10/unit slab — which is why summer bills spike disproportionately.

Tips to Reduce Your Electricity Bill

1. Stay within lower slabs. Because slab rates increase sharply, reducing consumption from 350 to 290 units can save more than the proportional reduction suggests — you avoid the higher slab entirely. 2. Replace old appliances. A 5-star rated AC uses 30-40% less electricity than a 3-star model. The upfront cost is recovered within 2-3 years through lower bills. 3. Use LED lighting. A 9W LED produces the same light as a 60W incandescent bulb. Switching 10 bulbs saves about 15 units/month. 4. Optimize AC usage. Set your AC to 24-26°C instead of 18-20°C. Every degree lower increases power consumption by approximately 6%. Use timers to avoid running AC all night.

Why is my electricity bill higher than expected?

Common reasons: meter reading estimate instead of actual reading (utilities sometimes estimate and adjust later), seasonal changes (AC in summer, heaters in winter), faulty appliances drawing excess power, or rate revisions you weren't aware of.

What is the difference between kW and kWh?

kW (kilowatt) is power — the rate of energy consumption. kWh (kilowatt-hour) is energy — the total consumption over time. Your meter measures kWh. A 1 kW appliance running for 3 hours consumes 3 kWh (3 units).

How do I read my electricity meter?

Digital meters display the current reading directly. For dial meters, read each dial left to right, recording the lower number when the pointer is between two digits. Subtract the previous reading from the current reading to get units consumed.

Electricity Bill Calculator — calculate your bill with slab rates
Unit Converter — convert between energy units
Percentage Calculator — calculate percentage savings
Budget Calculator — plan your monthly household expenses