Free Solar Tool
Solar Production Calculator
Enter your system size, region, and panel type to instantly estimate daily and annual kWh output, first-year electricity savings, and 25-year production — so you and your customers can make informed decisions before signing a proposal.
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Estimate Your Solar System's Output
Adjust the inputs below to match your system and location. Production estimates update instantly.
Typical residential: 5–12 kW. Your contractor's proposal will show the exact size.
Estimated solar production & savings
Daily output
28.0 kWh
Annual output
10,220 kWh
Annual savings
$1,635
25-yr savings
$38,519
System size
7.0 kW
Peak sun hrs
5/day
System eff.
80%
Yr 25 output
9,062 kWh
Savings estimates assume electricity rate stays constant. Savings may be higher if rates rise. 25-year output accounts for annual panel degradation. Does not include net metering credits, battery storage, or feed-in tariff income.
Ballpark estimate only
These figures are rough estimates for planning purposes only. Actual production depends on roof orientation, tilt, shading, local weather, and equipment selection. Always obtain a detailed site analysis and proposal from a licensed solar installer before making financial decisions.
📋 Important: All calculator results are ballpark estimates
Actual solar production depends on roof orientation, tilt angle, shading trees or structures, local microclimate, and specific equipment. This calculator uses regional averages for planning purposes. Always get a site analysis from a licensed solar installer before making purchasing decisions.
How Solar Production Is Estimated
System size × peak sun hours
The foundation of every solar production estimate is simple: system size in kW multiplied by daily peak sun hours equals the DC energy the panels receive each day under ideal conditions. A 7 kW system in a 5 sun-hour region generates up to 35 kWh of DC power on a clear day — before system losses are applied.
Apply system efficiency
Real-world AC output is always less than the DC nameplate figure. Inverter losses, wiring resistance, dust, temperature, and shading all reduce output. A system efficiency of 75–85% is realistic for most installations. Microinverters or DC power optimizers minimize mismatch losses and push efficiency toward the high end of that range.
Multiply by 365 for annual output
Multiplying the daily average output by 365 gives the annual production estimate. This uses a region's annual average sun hours — actual output is higher in summer and lower in winter. The annual figure is what matters for utility billing comparisons and payback calculations.
Multiply by electricity rate for savings
Annual kWh output multiplied by your local retail electricity rate gives the estimated annual bill reduction. If your utility has net metering, excess kWh can roll forward as credit — this calculator assumes all production offsets consumption at the retail rate, which is the most common net metering structure.
Apply annual degradation for 25-year view
Solar panels lose a small amount of output efficiency each year — typically 0.3–0.7%. This calculator compounds the degradation annually over 25 years (the standard panel warranty period) to show the cumulative production and savings over the full system life. Premium panels from LG, REC, and SunPower degrade at the low end; budget panels trend toward 0.7%.
What Affects Solar Production
Roof orientation
South-facing roofs in the Northern Hemisphere maximize production year-round. East or west-facing panels produce 15–20% less than south-facing. North-facing is the least ideal. This calculator assumes a south-facing install; your contractor's proposal will adjust for actual orientation.
Shading
Trees, chimneys, and neighboring buildings that shade even one panel in a string system can reduce output by 20–50%. Microinverters or power optimizers eliminate string-level mismatch, limiting shading impact to the individual shaded panels. Always have your installer run a shading analysis.
Temperature
Solar panels produce less power in high heat — efficiency typically drops about 0.35–0.5% per degree Celsius above 25°C (77°F). Hot climates like Arizona see meaningful derating in summer afternoon hours despite having more sun. System efficiency in this calculator partially accounts for this as an annual average.
Panel tilt
For maximum annual output, panel tilt should roughly equal the site's latitude. A 15° tilt in Georgia or a 35° tilt in New York produces more than a flat panel. Roof-mounted systems are typically installed at the roof's pitch angle, which may not be the optimal tilt.
Inverter type
String inverters are the most common and cost-effective. Microinverters (one per panel) or DC optimizers (with a string inverter) cost more but eliminate shading mismatch, enable panel-level monitoring, and generally push system efficiency 3–7 points higher.
Soiling and maintenance
Dust, bird droppings, and pollen reduce panel output, especially in dry climates. Rainfall cleans most panels naturally. An annual cleaning in dry climates can recover 2–5% of lost output. This calculator uses an average soiling factor baked into system efficiency.
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Common Questions About Solar Production
How many kWh does a solar system produce per day?
A 7 kW solar system in a region with 5 peak sun hours per day and 80% system efficiency produces about 28 kWh/day (7 × 5 × 0.80). Annual output would be roughly 10,220 kWh. Actual output varies daily with weather, shading, soiling, and seasonal sun angle changes. Most installers estimate within 5–10% of actual annual production for a well-placed system.
What is system efficiency in solar?
System efficiency accounts for all real-world losses between panel nameplate watts and actual AC power delivered to your home. Losses come from inverter conversion, wiring resistance, soiling, shading, and temperature derating. A well-designed system with microinverters or power optimizers runs at 75–85% system efficiency. String inverter systems in shaded environments may run 65–75%.
How accurate is this solar production estimate?
This calculator provides a planning-level estimate — useful for understanding the range of output and savings before getting a detailed proposal. It uses average peak sun hours by region and typical system efficiency. Professional solar designs use NASA PVWATTS or Aurora Solar with actual roof orientation, tilt, shading analysis, and granular weather data to produce ±5% accuracy estimates. Use this tool to set expectations; use a contractor's proposal for final sizing.
What size solar system do I need to offset my electricity bill?
Divide your annual kWh usage by (365 × peak sun hours × system efficiency) to find the system size needed for 100% offset. If you use 12,000 kWh/year in a 5 sun-hour region with 80% efficiency: 12,000 ÷ (365 × 5 × 0.80) = 8.2 kW. Most homeowners size to 80–100% offset; going larger may not be cost-effective unless you drive an EV or have high future usage.
Does this calculator account for seasonal variation?
Not directly — it uses an annual average peak sun hours figure for your region. In reality, production in June can be 40–60% higher than in December at northern latitudes. Your solar contractor's proposal will show a month-by-month production curve that accounts for seasonal variation, roof tilt, and orientation.
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Book a Free DemoAll calculations are ballpark estimates based on regional solar resource averages and should be verified with a licensed solar installer using site-specific analysis tools.