Expected Solar Production by State: How Much Should Your System Produce?

You're trying to figure out if your solar system is performing well. Your system produced 450 kWh last month. Is that good? To answer that question, you need to know what's expected for your specific location.

Solar production varies dramatically based on geographic location. A 10 kW system in Arizona produces completely different amounts than the same size system in Maine. Understanding your state's baseline helps you identify when underperformance is a real problem vs. just normal variation.

How Geographic Location Affects Solar Production

Solar irradiance is the amount of sunlight hitting the Earth's surface, measured in kilowatt-hours per square meter per day (kWh/m²/day). States with higher irradiance produce more electricity.

The sunniest states are in the Southwest (Arizona, Southern California, New Mexico, Utah). The cloudiest states are in the Pacific Northwest and Northeast. The difference is significant:

• Phoenix, AZ gets ~6.5 kWh/m²/day (extremely sunny)
• Los Angeles, CA gets ~5.5 kWh/m²/day (very sunny)
• Denver, CO gets ~5.3 kWh/m²/day (sunny)
• Atlanta, GA gets ~4.5 kWh/m²/day (moderate)
• Seattle, WA gets ~3.8 kWh/m²/day (cloudy)
• Boston, MA gets ~4.0 kWh/m²/day (cloudy)

This explains why a 10 kW system in Arizona produces roughly 50,000 kWh/year while the same size system in Seattle only produces 38,000 kWh/year. Location determines your baseline capacity.

Expected Annual Production by State

Here's the estimated kWh per kilowatt installed per year for each state. This assumes standard 25-year panels on a properly tilted roof with optimal orientation (south-facing in the northern hemisphere):

State	kWh per kW/year	Relative Production
Arizona	1,650	Excellent
California	1,550	Excellent
New Mexico	1,600	Excellent
Nevada	1,620	Excellent
Utah	1,550	Excellent
Colorado	1,520	Excellent
Texas	1,450	Very Good
Florida	1,400	Very Good
North Carolina	1,350	Very Good
Georgia	1,350	Very Good
Illinois	1,250	Good
New York	1,200	Good
New Jersey	1,200	Good
Massachusetts	1,150	Good
Pennsylvania	1,150	Good
Washington	1,050	Moderate
Oregon	1,100	Moderate

These numbers represent healthy systems with good installation quality and minimal soiling.

How to Calculate Your Expected Monthly Production

Formula: (System Size in kW) × (Annual kWh per kW for your state) ÷ 12 months = Average Monthly Production

Example: You have a 6 kW system in Arizona (1,650 kWh/kW/year).

6 kW × 1,650 kWh/kW = 9,900 kWh/year ÷ 12 months = 825 kWh/month average

But remember: this is an average. Summer months will be 25-50% higher. Winter months will be 30-50% lower. A sunny July might produce 1,200 kWh while a cloudy December produces 500 kWh — both normal.

Factors That Reduce Expected Production

The numbers above assume optimal conditions. These factors reduce production:

• Shading: 1% shadow loss per 1% of panel shading (non-linear impact with optimizers)
• Soiling: 5-25% loss from dust, pollen, bird droppings
• Inverter efficiency loss: 2-5% from DC-to-AC conversion
• Wiring and connection losses: 1-3% from resistance
• Temperature effects: 0.4-0.5% production loss per 1°C above 25°C

A healthy system operates at 75-85% of theoretical maximum. This accounts for all losses above.

Why Your Installer's Estimate Might Be Different

Your installer gave you a production estimate when you bought your system. That estimate might not match the state averages above because:

• They accounted for your specific roof pitch and orientation
• They factored in known shading from trees on your property
• They used micro-climate data for your specific address (not just statewide averages)
• They may have used outdated data or conservative estimates

If your actual production is within 10% of your installer's estimate, you're in good shape. If it's 20%+ below, investigate why.

Is Your System Underperforming?

Compare your actual annual production to the state average for your location. If you're below 90% of the state average, investigate why. If you're between 90-110%, you're performing normally.

Reasons for underperformance:

• Shading has developed (tree growth)
• Soiling is reducing output
• Panel or inverter failures
• Suboptimal installation quality

A professional can identify the specific cause and recommend fixes.