Methodology

1. Electricity Bill Calculator

For a given state/DISCOM, connection type, units consumed, sanctioned load, and billing period, we compute:

1. Slab-wise energy charges — units are allocated across the tariff's slab boundaries in order (e.g. the first 100 units at the first slab's rate, the next 100 at the second slab's rate, and so on), and each slab's units × rate are summed.
2. Fixed / demand charges — the tariff's per-kW fixed charge × your sanctioned load (kW) × number of months in the billing period.
3. Fuel Adjustment Charge (FAC/FPPPA) — units consumed × the configured per-unit surcharge, where applicable.
4. Meter rent — a flat per-month charge × number of months, where applicable.
5. Electricity duty — the state's duty percentage applied to (energy charges + fixed charges + FAC).
6. Government subsidy / free-unit schemes — where a state runs a free-unit or subsidy scheme (e.g. Delhi's 200-unit waiver, Punjab's 300-unit zero-bill scheme, Karnataka's Gruha Jyothi), we apply it exactly as published: most of these schemes are threshold-based — if your consumption is within the free limit the relevant charges are waived, but exceeding the limit (even by one unit) typically forfeits the waiver for that billing cycle, which is why a small change in units can cause a large jump in the estimated bill. Where a state offers a partial/capped subsidy instead (e.g. Delhi's 50% subsidy up to ₹800 for 201–400 units), that cap is applied instead.

The final estimate is gross total minus any applicable subsidy, floored at ₹0.

2. Appliance Electricity Cost Calculator

For each appliance you select, monthly energy use is estimated as wattage × hours used per day × quantity × 30 ÷ 1000 to get kWh/month, then multiplied by an approximate per-unit rate for your selected state to estimate cost. This is a rough load estimate — actual appliance draw varies by model, star rating, ambient temperature (for ACs/refrigerators), and usage pattern.

3. Rooftop Solar ROI & Savings Estimator

• Recommended system size assumes ~120 kWh generated per kW of installed capacity per month (a commonly used India-wide average; actual generation depends heavily on your city's solar irradiance, roof orientation, and shading), sized to cover roughly 80% of your monthly consumption, capped between 1 kW and 10 kW.
• Your new estimated bill is calculated by re-running the bill calculator on your remaining (non-solar-offset) units.
• Gross system cost uses an approximate ₹55,000/kW installation cost.
• Central government subsidy under PM Surya Ghar Muft Bijli Yojana is applied at the official published tiers: ₹30,000 for 1 kW, ₹60,000 for 2 kW, and ₹78,000 (capped) for 3 kW or more.
• Payback period = net system cost ÷ estimated annual savings.

Actual quotes from installers, your roof's usable area, local DISCOM net-metering rules, and any state-level top-up subsidy will all affect real-world figures.

4. What Is Not Modelled

To keep estimates honest, we're explicit about what these calculators currently leave out:

• Arrears, previous outstanding dues, late payment surcharges, or interest
• Minimum monthly/demand charges that some DISCOMs apply regardless of consumption
• Wheeling charges, cross-subsidy surcharges, or open-access charges for non-domestic categories
• Time-of-Day (TOD) / Time-of-Use tariffs (peak vs. off-peak rates)
• Industrial, agricultural, and other specialised tariff categories beyond domestic and commercial
• One-off adjustments a DISCOM may apply for a specific billing cycle

See our Disclaimer for the full estimation notice, and our Data Sources page for where the underlying tariff figures come from.