Electricity Bill Unit Rate Calculator

Under the Tamil Nadu government (TANGEDCO) subsidy scheme, every domestic consumer receives the first 100 units 100% free of charge on their bi-monthly bill. If you consume 240 units in a 2-month cycle, the first 100 units are billed at ₹0.00. The next 100 units (101–200) are billed at the subsidized rate of ₹2.35 per unit, and the remaining 40 units (201–240) are billed at ₹4.70 per unit.

For consumption up to 500 units bi-monthly: 0–100 units is ₹0.00 (Free), 101–200 units is ₹2.35/unit, 201–400 units is ₹4.70/unit, and 401–500 units is ₹6.30/unit. When total consumption exceeds 500 units, the first 100 units remain free, but units 101–400 are charged at ₹4.80/unit, 401–500 at ₹6.30/unit, 501–600 at ₹8.40/unit, 601–800 at ₹9.45/unit, and above 800 units at ₹10.50–11.55/unit.

In Kerala (KSEB), domestic consumers using up to 250 units per month (500 units bi-monthly) enjoy telescopic billing, where each slab is billed progressively (0–50 units at ₹3.30, 51–100 at ₹4.15, 101–150 at ₹5.30, 151–200 at ₹7.10, and 201–250 at ₹8.40). If monthly consumption exceeds 250 units, telescopic benefit is revoked and all units are billed at a single flat non-telescopic rate (ranging from ₹6.60 to ₹9.30 per unit) plus a 10% statutory electricity duty.

Under Section 3 of the Kerala Electricity Duty Act, a statutory 10% electricity duty is levied on the total energy charges of low-tension domestic consumers. This duty is calculated strictly on energy charges (excluding fixed charges and meter rent) and remitted to the state government.

To calculate units consumed, subtract the previous meter reading from the current meter reading: Units (kWh) = Current Reading − Previous Reading. For example, if your current reading is 15,350 and previous reading was 15,100, your total consumption for that billing cycle is 250 units (kWh).

To calculate your electricity bill with a unit rate: multiply your consumed units by the tariff per unit, then add fixed meter charges and statutory tax. Formula: Total Bill = (Total Units × Rate per kWh) + Fixed Charges + (Energy Cost × Tax Percentage).

Electricity is billed in Kilowatt-hours (kWh), where 1 Unit = 1,000 Watt-hours. To calculate units: Units (kWh) = (Appliance Wattage × Daily Hours Used × Days) ÷ 1,000. For instance, running a 1,500W air conditioner for 8 hours daily over 30 days consumes (1500 × 8 × 30) ÷ 1,000 = 360 units.

In slab-based tariff structures without proportionate scaling, higher bi-monthly consumption can push units into higher priced tariff brackets. However, regulated utilities like TANGEDCO and KSEB calibrate their bi-monthly slabs to double the monthly thresholds (e.g., 50 units/month becomes 100 units bi-monthly) so domestic consumers are not penalized by the 60-day billing cycle.

A single phase (1φ) connection delivers 230V AC power through one live wire and one neutral wire, suitable for homes with total load under 5 kW (lights, fans, TV, small AC). A three phase (3φ) connection delivers 415V AC through three live wires, designed for higher loads above 5 kW such as multiple air conditioners, water heaters, or commercial equipment. Three phase connections have higher fixed charges but provide more stable voltage for heavy appliances.

Energy charges are the variable cost based on how many units (kWh) you actually consume, calculated using your utility's slab-based or flat tariff rates. Fixed charges (also called demand charges or meter charges) are a flat monthly fee your electricity board levies regardless of consumption — they cover the cost of maintaining the grid connection, transformer infrastructure, and meter equipment. Your total bill = Energy Charges + Fixed Charges + Taxes/Duty.

A typical 1.5 Ton split AC rated at 1,500 Watts running for 8 hours per day consumes approximately 360 units (kWh) per month. At an average tariff of ₹7/unit, that translates to roughly ₹2,520/month. A 5-star rated inverter AC of the same capacity may consume only 900–1,100 Watts, bringing monthly consumption down to around 216–264 units and saving 25–40% on cooling costs.

Key strategies to lower your electricity bill: 1) Set AC temperature to 24°C instead of 18°C (saves up to 24% cooling energy). 2) Switch to LED bulbs (use 80% less power than incandescent). 3) Use 5-star rated appliances — especially AC, refrigerator, and washing machine. 4) Turn off appliances at the wall switch when not in use to avoid standby power drain. 5) Run heavy-load appliances like washing machines and water heaters during off-peak hours. 6) Clean AC filters monthly for optimal efficiency.

1 unit of electricity = 1 Kilowatt-hour (kWh) = 1,000 Watt-hours. It means consuming 1,000 Watts of power continuously for 1 hour. For example: a 100W bulb running for 10 hours = 1 unit; a 2,000W geyser running for 30 minutes = 1 unit; ten 10W LED bulbs running for 10 hours = 1 unit.

FPPCA (Fuel and Power Purchase Cost Adjustment) is a variable surcharge added to your electricity bill to account for fluctuations in fuel prices (coal, natural gas, oil) used by power generation plants. When fuel costs rise above the base tariff assumptions, the electricity regulatory commission allows discoms to pass on the incremental cost to consumers as FPPCA. It is typically stated as paise per unit and changes quarterly.

Yes, VoltCalc is completely free with no sign-up, no login, and no hidden charges. All calculations run entirely in your browser (client-side JavaScript) — your meter readings and consumption data are never sent to any server or stored anywhere.

Our calculators use the latest officially published tariff slabs from TNERC (Tamil Nadu Electricity Regulatory Commission) and KSERC (Kerala State Electricity Regulatory Commission). The calculated amounts closely match actual utility bills. Minor differences may arise from localized fuel surcharges (FPPCA), delayed payment penalties, or rounding variations applied by your specific electricity board office.

The Tamil Nadu and Kerala calculators on this website are configured specifically for LT-1A Domestic (residential) tariff categories. Commercial (LT-2), industrial (HT), and agricultural connections follow different tariff structures, demand charges, and power factor penalties. We recommend checking your state electricity board's official tariff order for non-domestic categories.

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Currently we offer dedicated slab-based calculators for Tamil Nadu (TANGEDCO) and Kerala (KSEB) with full subsidy and duty calculations. The Universal Unit Rate Calculator can be used for any Indian state or electricity utility — simply enter your per-unit tariff rate, fixed charges, and tax percentage from your latest bill to get an accurate estimate.

Go to the Appliance Load Estimator tab, adjust the wattage, quantity, and daily usage hours for each household appliance. The calculator instantly shows each appliance's monthly kWh consumption and cost. You can add custom appliances, remove ones you don't own, and set your local per-unit electricity rate at the top. The total monthly units shown can then be entered into the Tamil Nadu or Kerala calculator for an exact slab-based bill estimate.