How much electricity a rooftop solar system makes decides everything else: how big a system you need, how much of your bill it cancels and how fast it pays back. Here is how many units 1 kW to 10 kW of panels generate per day, month and year in each Indian state, and why your own meter may read a little differently.
Peak sun hours are the number of hours a day of full-strength sunlight (1,000 W per square metre) your location receives on average. A day with 10 hours of daylight might deliver only 5 peak sun hours, because the morning and evening sun is weak. Across the states covered here they run from 4.5 to 6.5.
The 0.78 performance ratio covers real-world losses: panels lose output when they are hot, dust and bird droppings block light, and some energy is lost in wiring and in the inverter that converts DC to AC. Together these take about 22% off the panel's rated output. This is exactly how the solar calculator estimates generation, so the tables below match what it shows for your state.
For 1 kW at the Indian average of 5 peak sun hours: 1 × 5 × 0.78 = 3.9 units a day, or about 1,424 units a year.
Peak sun hours are the values the calculator uses for each state. Monthly figures are the yearly total divided by 12; actual months vary (see the seasons section below).
| State | Peak sun hours | 1 kW: units/day | 1 kW: units/month | 1 kW: units/year | 3 kW: units/day | 3 kW: units/year |
|---|---|---|---|---|---|---|
| Rajasthan | 6.5 | 5.1 | ~155 | ~1,861 | 15.2 | ~5,548 |
| Gujarat | 5.8 | 4.5 | ~137 | ~1,643 | 13.6 | ~4,964 |
| Delhi, Haryana, Maharashtra | 5.5 | 4.3 | ~131 | ~1,570 | 12.9 | ~4,709 |
| Telangana | 5.4 | 4.2 | ~128 | ~1,533 | 12.6 | ~4,599 |
| Karnataka, Uttar Pradesh | 5.3 | 4.1 | ~125 | ~1,496 | 12.4 | ~4,526 |
| Punjab | 5.2 | 4.1 | ~125 | ~1,496 | 12.2 | ~4,453 |
| Andhra Pradesh, Assam, Bihar, Chhattisgarh, Goa, Himachal Pradesh, Jharkhand, Madhya Pradesh, Odisha, Tamil Nadu, Uttarakhand | 5.0 | 3.9 | ~119 | ~1,424 | 11.7 | ~4,271 |
| Kerala, West Bengal | 4.5 | 3.5 | ~107 | ~1,278 | 10.5 | ~3,833 |
The gap between states is large. A kilowatt in Rajasthan produces about 45% more than one in Kerala, so a home in Kerala needs a bigger system for the same bill. Our how many solar panels do I need guide turns this into system sizes and panel counts.
At 5 peak sun hours (the Indian average and the calculator's default for states without their own figure):
| System size | Units per day | Units per month | Units per year |
|---|---|---|---|
| 1 kW | 3.9 | ~119 | ~1,424 |
| 2 kW | 7.8 | ~237 | ~2,847 |
| 3 kW | 11.7 | ~356 | ~4,271 |
| 4 kW | 15.6 | ~475 | ~5,694 |
| 5 kW | 19.5 | ~593 | ~7,118 |
| 10 kW | 39.0 | ~1,186 | ~14,235 |
Scale these by your state's peak sun hours divided by 5. In Delhi (5.5 hours), for example, multiply by 1.1.
Installer guides in India commonly quote a rule of thumb of 4–5 units a day per kW, with yearly yields of around 1,400–1,500 units per kW in cities such as Delhi and Mumbai, higher in Rajasthan and Gujarat and lower in the North-East. The calculator's figures sit in the same range: 1,570 units per kW a year in Delhi and 1,424 at the national average. Its Rajasthan figure, about 1,860 units, is at the optimistic end, so treat it as the best case for a clean, well-angled, unshaded roof.
Generation is not the same every month. The tables show yearly averages, and the calculator also draws a month-by-month bar chart for your state. Its seasonal profiles show the pattern most owners see:
Under net metering this evens out: surplus units in sunny months are credited against your bill and can offset grid use in weaker months, subject to your DISCOM's settlement rules. See net metering explained.
Units only matter for what they save. The calculator assumes you use about 65% of your solar units yourself, each one saving your full tariff, and export the rest at your DISCOM's buyback rate. For example, a 3 kW on-grid system in Delhi (₹7/kWh tariff, ₹3.50 buyback) makes about 4,709 units a year: 3,061 used at home save ₹21,427 and 1,648 exported earn ₹5,768, so about ₹27,200 a year. After the ₹78,000 PM Surya Ghar subsidy, the calculator puts the net cost at about ₹1.32 lakh and the payback at 4.8 years. See the solar panel cost guide for prices by size.
Your inverter app or display shows how many units the system has produced, and your net meter shows imports and exports. Compare a full year's generation with the yearly figure for your state and system size above, rather than a single day or month. If a system is consistently more than about 15–20% below the expected yearly figure even after allowing for its direction and any shade, ask the installer to check for soiling, shading, a faulty panel or string, or inverter errors.
Pick your state and enter your bill. The calculator shows daily and yearly units, a month-by-month chart, savings and payback.
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