A single 400W solar panel — the most common wattage sold in 2026 — produces approximately 1.2–2.6 kWh of electricity per day depending on your location, panel orientation, and weather. Over a full year, that same panel generates 440–950 kWh. The variation reflects how much sunlight your location actually receives: a panel in Phoenix sees far more peak sun hours than the same panel in Seattle. This guide gives you the actual production numbers for every major US location and every common panel size.
How Much Power Does a Solar Panel Produce? The Basic Math
Solar panel output is determined by a simple formula:
Daily output (kWh) = Panel wattage (kW) × Peak sun hours × System efficiency
Peak sun hours (PSH) is the average number of equivalent full-sunlight hours your location receives per day — not total daylight hours, but the hours equivalent to direct 1,000 W/m² irradiance. A typical grid-tied solar system operates at about 80% efficiency (accounting for inverter losses, wiring resistance, temperature effects, and soiling).
For a 400W panel (0.4 kW):
Phoenix (6.5 PSH): 0.4 kW × 6.5 × 0.80 = 2.08 kWh/day
Dallas (5.5 PSH): 0.4 kW × 5.5 × 0.80 = 1.76 kWh/day
Atlanta (5.0 PSH): 0.4 kW × 5.0 × 0.80 = 1.60 kWh/day
New York (4.5 PSH): 0.4 kW × 4.5 × 0.80 = 1.44 kWh/day
Seattle (3.5 PSH): 0.4 kW × 3.5 × 0.80 = 1.12 kWh/day
Solar Panel Output by Location — US Cities
The following table shows daily and annual output for a single 400W panel, by city, assuming optimal south-facing orientation and 80% system efficiency:
Phoenix, AZ — 6.5 PSH — 2.08 kWh/day — 760 kWh/year
Las Vegas, NV — 6.3 PSH — 2.02 kWh/day — 737 kWh/year
Tucson, AZ — 6.2 PSH — 1.98 kWh/day — 724 kWh/year
El Paso, TX — 6.0 PSH — 1.92 kWh/day — 701 kWh/year
Albuquerque, NM — 6.0 PSH — 1.92 kWh/day — 701 kWh/year
Los Angeles, CA — 5.8 PSH — 1.86 kWh/day — 678 kWh/year
Denver, CO — 5.5 PSH — 1.76 kWh/day — 643 kWh/year
Dallas, TX — 5.5 PSH — 1.76 kWh/day — 643 kWh/year
San Antonio, TX — 5.4 PSH — 1.73 kWh/day — 631 kWh/year
Miami, FL — 5.3 PSH — 1.70 kWh/day — 619 kWh/year
Jacksonville, FL — 5.2 PSH — 1.66 kWh/day — 608 kWh/year
Atlanta, GA — 5.0 PSH — 1.60 kWh/day — 584 kWh/year
Nashville, TN — 4.8 PSH — 1.54 kWh/day — 562 kWh/year
Charlotte, NC — 4.8 PSH — 1.54 kWh/day — 562 kWh/year
Chicago, IL — 4.5 PSH — 1.44 kWh/day — 526 kWh/year
Washington DC — 4.5 PSH — 1.44 kWh/day — 526 kWh/year
New York, NY — 4.5 PSH — 1.44 kWh/day — 526 kWh/year
Philadelphia, PA — 4.4 PSH — 1.41 kWh/day — 514 kWh/year
Boston, MA — 4.2 PSH — 1.34 kWh/day — 491 kWh/year
Minneapolis, MN — 4.5 PSH — 1.44 kWh/day — 526 kWh/year
Portland, OR — 3.8 PSH — 1.22 kWh/day — 445 kWh/year
Seattle, WA — 3.5 PSH — 1.12 kWh/day — 409 kWh/year
Output by Panel Wattage — All Common Sizes
Panel wattages sold in 2026 range from 250W (older panels still in operation) to 500W+ (premium residential panels). The following shows annual production in a typical US location (4.5 PSH, good US average):
250W panel: 0.25 × 4.5 × 0.80 × 365 = 329 kWh/year
300W panel: 0.30 × 4.5 × 0.80 × 365 = 394 kWh/year
350W panel: 0.35 × 4.5 × 0.80 × 365 = 460 kWh/year
400W panel: 0.40 × 4.5 × 0.80 × 365 = 526 kWh/year
450W panel: 0.45 × 4.5 × 0.80 × 365 = 591 kWh/year
500W panel: 0.50 × 4.5 × 0.80 × 365 = 657 kWh/year
Note: Premium 500W panels (SunPower Maxeon, REC Alpha) have higher efficiency but occupy roughly the same roof area as a 400W panel. The extra wattage comes from better cell technology, not a larger panel. This makes high-efficiency panels particularly valuable when roof space is limited.
What Reduces a Solar Panel’s Actual Output?
The production figures above assume optimal conditions — south-facing, unshaded, clean panels, moderate temperatures. Real-world deductions include:
Roof orientation: Due south (azimuth 180°) = 100% of rated output. Southwest or Southeast = 90–95%. East or West = 78–88%. Northeast or Northwest = 55–70%. North-facing = 40–55%.
Tilt angle: Optimal tilt is approximately equal to your latitude (33° in Atlanta, 41° in Chicago, 47° in Seattle). Flat roof panels lose 5–15% compared to optimally tilted panels. Steeply pitched roofs (>45°) lose 5–10% in summer but gain in winter.
Shading: Even partial shading of one panel in a string inverter system reduces the output of the entire string, not just the shaded panel. A single shaded panel can reduce string output by 30–60%. Microinverters and DC power optimizers eliminate this string effect, allowing each panel to perform independently.
Temperature: Solar panels produce less power when hot. The temperature coefficient (approximately -0.3%/°C for modern panels) means a panel at 65°C (a common summer operating temperature in hot climates) produces about 12% less than its STC rating at 25°C. HJT and IBC panels have the lowest temperature coefficients (-0.24 to -0.27%/°C) and outperform standard panels in hot weather.
Soiling: Dust, pollen, bird droppings, and grime reduce output by 1–5% in most climates, up to 15–25% in desert or agricultural areas with heavy soiling. Annual cleaning restores full production.
Degradation over time: Modern panels degrade at 0.25–0.55% per year, depending on technology. By year 25, a panel retains approximately 85–94% of its original rated output.
How Many Panels Do You Need to Power Your Home?
To determine how many panels your home needs, the starting point is your annual electricity consumption from utility bills. The average US household uses 10,500 kWh/year.
System size needed (kW) = Annual consumption (kWh) ÷ (PSH × 365 × 0.80)
For average US home (10,500 kWh) in New York (4.5 PSH):
10,500 ÷ (4.5 × 365 × 0.80) = 10,500 ÷ 1,314 = 8.0 kW system
Number of 400W panels: 8,000 ÷ 400 = 20 panels
For average US home in Phoenix (6.5 PSH):
10,500 ÷ (6.5 × 365 × 0.80) = 10,500 ÷ 1,898 = 5.5 kW system
Number of 400W panels: 5,500 ÷ 400 = 14 panels
This is why system sizing must be location-specific — the same home needs 40% more panels in Seattle than in Phoenix to produce the same annual electricity.
Monitoring Your Panel’s Actual Output
Modern solar installations include monitoring software that shows real-time and historical production data. String inverter monitoring platforms (SolarEdge mySolarEdge, SMA Sunny Portal, Fronius Solar.web) show system-level data. Microinverter monitoring (Enphase Enlighten) shows production per individual panel — allowing you to spot underperforming panels caused by shading, soiling, or failure.
As a benchmark for your system’s actual performance, use NREL’s PVWatts calculator (pvwatts.nrel.gov) to calculate expected annual production for your specific address, panel count, orientation, and tilt. Compare PVWatts estimates against your actual monitoring data — a shortfall of more than 10–15% from the PVWatts estimate warrants investigation (check for new shading, soiling, or inverter faults).
Frequently Asked Questions
How many kWh does a 400W solar panel produce per day?
A 400W panel produces 1.12–2.08 kWh per day depending on location. In Phoenix (6.5 peak sun hours), expect about 2.08 kWh/day. In New York (4.5 PSH), expect about 1.44 kWh/day. In Seattle (3.5 PSH), expect about 1.12 kWh/day. Over a full year, a 400W panel produces 410–760 kWh depending on location.
How many solar panels does it take to produce 1,000 kWh per month?
To produce 1,000 kWh/month (33.3 kWh/day), you need to work backward from your location’s peak sun hours. In a typical US location (4.5 PSH): Array needed = 33.3 kWh ÷ (4.5 × 0.80) = 9.25 kW. Number of 400W panels: 9,250 ÷ 400 = approximately 23 panels.
Do solar panels produce electricity on cloudy days?
Yes — panels produce 10–25% of rated output on overcast days, rising to 40–70% on partly cloudy days. They produce zero at night (no light = no photovoltaic effect). In cloudy climates, this reduced production is accounted for in the lower peak sun hours figure used for system sizing — so a properly sized system in Seattle still covers 100% of annual energy needs, just through a larger array than you’d install in Phoenix.
What is the highest-producing residential solar panel in 2026?
The highest-wattage residential panels in 2026 include the SunPower Maxeon 7 (500W, 24.1% efficiency), REC Alpha Pure-R (430W, 22.3% efficiency), and Canadian Solar HiHero (430W HJT). These panels produce more power per square foot of roof area than standard TOPCon panels, making them the best choice when roof space is limited.
Summing Up
A single 400W solar panel produces 1.12–2.08 kWh/day depending on your location, and 410–760 kWh over a full year. The entire US residential solar system — which typically consists of 15–25 panels — produces enough to cover an average home’s entire electricity consumption. The exact production for your home depends on your local peak sun hours, panel orientation, shading, and system efficiency. For an accurate production estimate and system quote for your specific address, call (855) 427-0058 to get connected with a local installer who will run the numbers for your roof.
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