Solar Energy Calculator
Estimate daily, monthly, and annual solar energy generation from your PV system capacity, peak sun hours, and performance ratio.
Calculate Solar Energy Generation
Enter your installed PV capacity, average peak sun hours, performance ratio, and an optional degradation adjustment.
| Calculation | Value | Unit |
|---|---|---|
| Installed DC Capacity | — | kWp |
| Peak Sun Hours | — | hours/day |
| Performance Ratio | — | % |
| Degradation Adjustment | — | % |
| Annual Generation | — | kWh/year |
| Annual Generation | — | MWh/year |
| Annual Generation | — | GWh/year |
What Is a Solar Energy Calculator?
A solar energy calculator estimates electricity generation from a photovoltaic system over a selected period. It combines installed PV capacity with peak sun hours and a performance ratio representing real-world system effects.
It is useful for preliminary planning, comparisons, education, and high-level solar generation estimates. It is not a replacement for a detailed site-specific energy-yield study.
Why Use a Solar Energy Calculator?
Estimate Electricity Generation
Estimate how many kWh, MWh, or GWh a PV system could generate.
Compare System Sizes
Change the installed capacity and solar resource assumptions to see how expected production changes.
Support Early Solar Planning
Use the result as a preliminary estimate before detailed engineering and energy-yield modeling.
How Does Solar Energy Calculation Work?
The basic relationship uses installed DC capacity, peak sun hours, and performance ratio.
Performance ratio is entered as a percentage and converted to a decimal during calculation.
Solar Energy Calculation Formula
Daily Generation
Monthly Generation
Annual Generation
Capacity Factor
Worked Solar Energy Example
Assume a 100 kWp system, 5.5 peak sun hours/day, and an 80% performance ratio.
Daily: 100 × 5.5 × 0.80 = 440 kWh/day.
Annual: 100 × 5.5 × 365 × 0.80 = 160,600 kWh/year or 160.6 MWh/year.
Understanding Peak Sun Hours
Peak sun hours are equivalent full-sun hours based on an irradiance reference of 1,000 W/m². They are not simply the number of daylight hours.
Why Location Matters
Solar resource varies with season, latitude, weather, atmospheric conditions, orientation, terrain, and other factors. Detailed studies should use location-specific solar-resource data.
Understanding Performance Ratio
Performance ratio provides a simplified way to account for practical PV system losses and operating effects.
Common Losses
- Module temperature losses
- Soiling and dust
- Shading
- Module mismatch
- DC and AC cable losses
- Inverter losses
- Transformer losses
- Availability and downtime
- Clipping and operating constraints
Solar DC Capacity vs AC Capacity
PV capacity is commonly stated as DC module capacity, while inverter and grid capacity are normally stated on the AC side. This calculator uses DC PV capacity as the primary input.
It does not model detailed DC/AC ratio, clipping, inverter loading, curtailment, or dispatch behavior.
Solar Energy for Utility-Scale PV Plants
The same preliminary formula can be applied to large PV plants. For example, 1,500 MWp at 5.5 peak sun hours/day and 80% PR gives:
This is a simplified estimate and should not be treated as a bankable energy-yield result.
What Affects Actual Solar Energy Production?
Solar Irradiance
Clouds, seasons, atmospheric conditions, and local climate affect available solar energy.
Temperature
PV output generally changes with cell temperature and the module temperature coefficient.
Soiling and Shading
Dust, dirt, row shading, structures, terrain, and vegetation can reduce production.
Availability
Equipment faults, maintenance, grid restrictions, and other downtime can reduce annual generation.
Tracking
Tracking systems change the solar resource captured by the array and require project-specific modeling.
Common Solar Energy Calculation Mistakes
- Confusing kW of power with kWh of energy.
- Using daylight hours instead of peak sun hours.
- Assuming rated module power is produced throughout the day.
- Ignoring real-world losses.
- Using generic PSH values for detailed project studies.
- Confusing DC capacity with AC capacity.
- Treating a preliminary calculator as a bankable yield assessment.
Limitations of This Calculator
This tool provides a simplified preliminary estimate. It does not individually model hourly weather, module temperature, inverter curves, clipping, bifacial gain, albedo, tracker geometry, row-to-row shading, curtailment, detailed availability, or multi-year degradation.
Frequently Asked Questions
How much energy does a 1 kW solar system produce per day?
It depends on the location and system performance. At 5 peak sun hours and 80% PR, 1 kWp would produce about 4 kWh/day.
What is the formula for solar energy generation?
A common preliminary formula is PV capacity × peak sun hours × performance ratio.
What are peak sun hours?
They are equivalent hours of solar irradiation at an average reference irradiance of 1,000 W/m².
What is performance ratio?
It is a simplified measure representing the practical relationship between theoretical and expected PV output after system effects and losses.
Can this be used for a 1 MW or 100 MW plant?
Yes, for preliminary estimates. Detailed utility-scale studies require site-specific energy-yield modeling.
Does this calculator include panel efficiency?
Not separately. Module efficiency is reflected in the rated DC capacity entered by the user.
Does it account for degradation?
It includes an optional simple degradation adjustment, but not a complete lifetime degradation model.
Is solar energy the same as solar power?
No. Power is the rate of production, while energy is production accumulated over time.
Can it calculate exact generation?
No. Actual generation depends on site, weather, equipment, losses, availability, and grid conditions.
Can I use it for rooftop solar?
Yes, it can provide a preliminary rooftop PV generation estimate.