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Solar Panel Calculator

Ecology

Estimate daily and annual solar energy output and electricity bill savings for home or business. Enter system size, sun hours, panel efficiency, and local electricity rate.

1100
18
1025
$0.01$0.25

Daily Energy (kWh)

4.5
Annual Energy (kWh)
1,642.5
Annual Savings ($)
$164

This calculator computes your Daily Energy (kWh), Annual Energy (kWh), Annual Savings ($) from the values you enter.

Inputs
System Size (kW)Peak Sun Hours per DayPanel Efficiency (%)Electricity Rate ($/unit)
Outputs
Daily Energy (kWh)Annual Energy (kWh)Annual Savings ($)

What is a Solar Panel?

A Solar Panel Calculator estimates the electrical energy a photovoltaic system produces every day and over a full year, and translates that energy into an annual rupee saving on your electricity bill. You enter four values — the rated system size in kilowatts, the average peak sun hours your location receives each day, the efficiency of your panels, and the electricity tariff you pay — and the calculator instantly returns daily generation in kWh, annual generation in kWh, and annual savings in ₹. This gives homeowners, businesses, and solar installers a fast, no-engineering-degree-required way to assess whether rooftop solar makes financial sense before committing to an installation.

India adds context that makes this calculator especially useful. The country sits firmly in the global solar belt, receiving 4.5 to 6.5 peak sun hours per day across most of its landmass. The Ministry of New and Renewable Energy (MNRE) has set an ambitious national target of 500 GW of solar capacity by 2030, and residential tariff rates from DISCOMs typically range from ₹5 to ₹10 per unit — meaning every kWh your panels generate replaces electricity you would otherwise purchase at that rate.

How to use this Solar Panel calculator

  1. Set System Size (kW): Use the slider or type your planned installation capacity. A typical 3BHK Indian home uses 8–12 kWh per day and is usually served by a 3–5 kW system. If you are unsure of the right size, start with the Solar Panel Wattage Calculator first.

  2. Set Peak Sun Hours per Day: Enter the average peak sun hours for your city. Rajasthan and Gujarat average 5.5–6.5 hours; Maharashtra and Karnataka average 5–5.5 hours; West Bengal and the north-east average 4–4.5 hours. The MNRE's solar atlas or tools like Solargis provide district-level data.

  3. Set Panel Efficiency (%): Enter the efficiency rating printed on your panel datasheet. If you have not yet chosen panels, use 18% for a standard monocrystalline module. Drag the slider right for premium panels (22–25%) or left for older polycrystalline stock (14–16%).

  4. Set Electricity Rate (₹/unit): Open your last electricity bill and locate the per-unit tariff. If you are on a slab tariff, use the rate that applies to your highest consumption slab — this is the rate solar most effectively displaces. The default of ₹8/unit is close to the average residential tariff across major states.

  5. Read the results: The Daily Energy figure in the result card is your key output. Confirm it is at least 80% of your typical daily consumption to ensure the system meaningfully offsets your bill. The annual savings figure tells you your annual financial benefit at the tariff you entered.

Formula & Methodology

Daily generation:

> Daily kWh = System Size (kW) × Peak Sun Hours (h/day) × (Panel Efficiency / 100)

Annual generation:

> Annual kWh = Daily kWh × 365

Annual savings:

> Annual Savings (₹) = Annual kWh × Electricity Rate (₹/kWh)

Variable definitions:

| Variable | Unit | Description |
|---|---|---|
| System Size | kW | Total rated DC capacity of all panels combined |
| Peak Sun Hours | h/day | Hours per day of sunlight at irradiance ≥ 1,000 W/m² |
| Panel Efficiency | % | Fraction of incident solar energy converted to electricity |
| Electricity Rate | ₹/kWh | Per-unit tariff charged by your DISCOM |

Worked example:

A 5 kW system in Pune (5 sun hours/day), using 18% efficient panels, at ₹8/unit:

- Daily kWh = 5 × 5 × 0.18 = 4.5 kWh
- Annual kWh = 4.5 × 365 = 1,642.5 kWh
- Annual Savings = 1,642.5 × ₹8 = ₹13,140

Important assumptions and limitations:

This model applies efficiency as a uniform derating factor, effectively collapsing inverter efficiency, temperature coefficient losses, wiring losses, and soiling into a single percentage. In practice, a well-designed system with a quality string inverter operates at an overall system efficiency of 75–85%, which the formula's efficiency input approximates. For a more granular breakdown that separates panel efficiency from system losses, see the Solar Panel Wattage Calculator, which uses an explicit system losses field. The Hydroelectric Power Calculator follows a similar physics-first approach for water-based generation.

Frequently Asked Questions

A solar panel calculator estimates the daily and annual electricity a photovoltaic (PV) system will generate, based on the system's rated capacity, the average peak sun hours at your location, and the efficiency of your panels. It then converts that energy figure into an annual bill saving by applying your local electricity tariff. The result gives you a quick, data-driven sense of what a rooftop solar installation can actually deliver.
The calculator gives a reliable first-order estimate, not a certified engineering yield report. Real-world output is affected by panel soiling, shading, inverter losses, temperature derating, and inter-row spacing — none of which are captured in this simplified model. Treat the figure as a planning benchmark; a licensed solar installer will run a full simulation (typically using PVSyst or equivalent software) before commissioning.
Mainstream monocrystalline panels sold in India today carry efficiencies between 19% and 22%. Older polycrystalline modules sit closer to 15–17%. Premium TOPCon and HJT panels can reach 23–25% but carry a price premium. The calculator's default of 18% is a safe, conservative assumption for a new residential system using mid-range monocrystalline panels.
India is one of the world's sunniest countries, with most of the landmass receiving 4.5 to 6.5 peak sun hours per day on an annual average basis. Rajasthan, Gujarat, and Madhya Pradesh consistently see 5.5–6.5 hours, while the north-eastern states and coastal Kerala average closer to 4–5 hours. Enter the figure specific to your district — state nodal agencies and the MNRE solar resource maps are the most reliable reference.
Use the per-unit (kWh) rate on your latest electricity bill from your DISCOM. Residential tariffs in India typically range from ₹4 to ₹10 per unit depending on the state and slab. If you are on a time-of-use tariff, use the weighted average rate across your typical usage hours for the most realistic savings estimate.
No — the calculator focuses on energy output and gross savings, not financial payback or subsidy amounts. Under the PM Surya Ghar Muft Bijli Yojana, households installing up to 2 kW receive a central subsidy of ₹30,000 per kW; systems between 2 kW and 3 kW attract ₹18,000 per kW for the additional capacity. Factor the subsidy into your total cost estimate separately to arrive at a net payback period.
Divide the net installation cost (after subsidies) by the annual savings figure this calculator produces. For example, a 5 kW system costing ₹2,00,000 after subsidy saving ₹40,000 per year has a payback period of 5 years. Most residential systems in India recover their cost within 4–7 years, then generate free electricity for the remaining 18–20 years of panel life.
System size, measured in kilowatts (kW), is the total rated capacity of your entire installation — the sum of all individual panel wattages. A panel's wattage (W) is the output of a single panel under standard test conditions. If you need help deciding how many panels of a specific wattage add up to meet your energy requirement, use the [Solar Panel Wattage Calculator](/solar-panel-wattage-calculator/) to work backwards from your daily consumption.
Yes, in terms of raw energy production — doubling the system size doubles the kWh output, all else equal. However, practical limits exist: your roof area constrains how many panels you can fit, your DISCOM connection may cap the permissible export under net metering, and self-consumption determines how much of the generation you actually offset. Excess generation exported to the grid is typically compensated at a lower feed-in tariff than the full retail rate.
Rooftop solar is the most accessible renewable option for urban and semi-urban Indian households because it requires no special permits beyond the DISCOM interconnection approval and works on almost any south-facing roof. Wind energy requires minimum wind speeds of around 5–6 m/s consistently — suitable mainly for rural or coastal sites. You can compare estimated annual outputs using the [Wind Turbine Calculator](/wind-turbine-calculator/) and [Hydroelectric Power Calculator](/hydroelectric-power-calculator/).
Yes. The system size slider goes up to 100 kW, which covers most commercial rooftop systems. For larger ground-mounted utility-scale plants, simply note that the formula scales linearly — multiply the per-kW output by your total plant capacity. Commercial consumers in India typically face tariffs of ₹8–12 per unit, making the financial case for solar even more compelling than for residential consumers.
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rooftop solar calculator Indiasolar energy output calculatorsolar power savings calculatorPV system calculatorsolar panel ROI calculator