Where the figures come from
Reference values come from government guidelines, state electricity regulatory commission orders, court rulings and dated, named industry sources. Each state page shows the date its figures were last checked and links to every source. A figure we can’t trace is marked “not verified” and never prefilled. The sources for each calculator are listed under it below.
Home solar calculator
Your price per unit is your monthly bill divided by the units used. The suggested size is your monthly units divided by what 1 kW makes a month in your state (120 units for the India average), rounded up to the nearest half kW and capped by your roof area at 100 sq ft per kW. Installed prices use published 2026 ranges for systems with DCR panels: 1 kW ₹1.20 to ₹1.30 lakh, 2 kW ₹1.80 to ₹1.90 lakh, 3 kW ₹2.30 to ₹2.40 lakh, 5 kW ₹3.25 to ₹3.75 lakh and 10 kW ₹5.80 to ₹6.50 lakh, with straight lines between those points and the 10 kW rate per kW above it. The subsidy follows PM Surya Ghar (see below). Savings count only the units you use yourself, at your current price per unit. The EMI line assumes 10% down and a 10-year loan at 5.75% up to ₹2 lakh or 7.9% above.
Sources: thewire.in, english.loktej.com, surgepv.com, ksquareenergy.com price list, March 2026.
Solar generation calculator
Units per kW for each month come from PVGIS 5.3 (European Commission Joint Research Centre) using the PVGIS-ERA5 weather record for 2005 to 2023, at each state or UT capital: 1 kW of crystalline silicon panels, 14% system losses, building-mounted, facing south at the best tilt. The India average is 1,440 units per kW a year, which matches the mean of the 36 state figures (1,438). Any loss you enter for shade or dust is taken off the total. The 25-year figure reduces output by 0.5% a year for panel ageing.
Sources: PVGIS 5.3, European Commission JRC.
PM Surya Ghar subsidy calculator
Homes get ₹30,000 per kW for the first 2 kW and ₹18,000 for the third, with nothing above 3 kW (₹78,000 at most). In special category states and UTs (Uttarakhand, Himachal Pradesh, Jammu and Kashmir, Ladakh, the North Eastern states including Sikkim, Andaman and Nicobar, Lakshadweep) the rates are ₹33,000 and ₹19,800 (₹85,800 at most). Housing societies and RWAs get ₹18,000 per kW for common facilities, counted up to 3 kW per home and 500 kW in total. State top-ups are not included.
Sources: MNRE PM Surya Ghar guidelines, 8 July 2025 (PDF).
Solar EMI calculator
EMI = P × r × (1 + r)n ÷ ((1 + r)n − 1), where P is the loan, r the monthly rate and n the months. If you leave fields empty we use: the midpoint of the installed price range, a 10% down payment, 10 years, and 5.75% for loans up to ₹2 lakh or 7.9% above (SBI Surya Ghar rates; the scheme links rates to repo + 0.5%, and the repo rate was 5.25% in August 2026). The “subsidy into the loan” figure recalculates the EMI on the loan minus the subsidy over the same term. The bill saving uses the same units and rate as the home calculator.
Sources: SBI Surya Ghar loan terms, MNRE PM Surya Ghar guidelines, 8 July 2025 (PDF), RBI policy, August 2026 (India Infoline).
Electricity unit calculator
Units (kWh) = watts × quantity × hours ÷ 1,000. A month is the daily figure times the days you enter (30 if empty); a year is twelve months. 1 HP is taken as 746 watts. The result uses the rated power, so appliances that cycle on and off will use less.
Home load calculator
Connected load is the sum of watts × quantity. Daily units are watts × quantity × hours × the share of time the appliance draws full power, divided by 1,000. That share is 30% for a fridge (compressor running), 65% for an inverter AC, 85% for a non-inverter AC, 80% for a geyser, 60% for an iron, 70% for an induction cooktop, 50% for a washing machine and 100% for everything else. Wattages are typical ratings for each type and can be off by 20% or more for a particular model; your appliance label is the better figure. The solar size is monthly units divided by what 1 kW makes a month in your state, rounded up to the next half kW.
Inverter battery backup calculator
Backup hours = Ah × battery voltage × usable share × 0.85 inverter efficiency ÷ load in watts. Battery voltage is 12 V per battery in series. Usable share is 70% to 85% for tubular lead-acid (heavier loads and the inverter’s low-voltage cut-off reduce it) and 90% to 95% for lithium (LFP), which gives the range shown. Inverter size is the load divided by a 0.8 power factor, rounded up to the next standard VA rating. The “brand formula” line uses Ah × volts × 95% ÷ load, as many battery makers do.
Sources: Livguard backup formula.
Solar roof area calculator
We allow 100 sq ft of shade-free roof per kW, including spacing between rows and a path for cleaning. Panels = roof area ÷ (100 × panel watts ÷ 1,000), rounded down; system size = panels × panel watts. Monthly units and subsidy use the same rules as the generation and subsidy calculators. A 540 Wp panel is about 2,272 × 1,133 mm per current datasheets.
EV running cost calculator
Monthly charging units are distance a day × 30 × the vehicle’s energy use: 0.035 units per km for a scooter, 0.165 for a car and 0.055 for an auto or cargo three-wheeler, from published 2026 figures. You can replace these with your own vehicle’s figure. Cost uses your home rate (₹8 a unit if empty), the public fast-charger rate (₹20 a unit if empty; public networks charge about ₹15 to ₹25), or the average of the two for “half and half”. The 5-year saving holds today’s fuel and power prices steady. The solar needed to cover charging is monthly units ÷ 120.
Sources: meraev.com, bgauss.com, komaki.in, greentax.in public charging tariffs, chargezone.co.in.
Solar park (open access) calculator
Your current price per unit is your monthly bill divided by the units you used. The solar price is then adjusted for power lost on the way and for units deducted when you bank power, and the grid fees are added on top.
Co-owning the plant (group captive) = effective solar price + wheeling + transmission + other fees
Just buying the power (third-party PPA) = the above + cross-subsidy fee + extra DISCOM fee
Sources: feeds.optenpower.com, solarsure.in, qbitsenergy.com.
Business rooftop calculator
Yearly solar units are system size multiplied by the units one kW makes in a year, reduced each year by panel degradation if you enter it. Buying the system saves your current per-unit price on every solar unit, minus maintenance. Paying per unit saves the difference between your current price and the RESCO price. The tax saving counts only the 40% first-year accelerated depreciation claim.
Sources: sunwavetech.com, heavengreenenergy.com, enerparc.in.
What the calculators leave out
Your grid price is held flat for the whole period, so savings are understated if tariffs rise. Time-of-day tariffs, demand charges, electricity duty changes, one-time connection fees and state top-up subsidies are not modelled. Treat the results as a planning estimate and confirm every figure in your final offer, your bank’s sanction letter and your DISCOM’s current order.
How often figures are checked
A daily watcher flags new commission orders and rulings, and we re-check a state’s figures when one changes a charge. Each page shows when it was last updated.