How Much Should a 6kW Solar System Produce Per Month?
Last updated: 2026-04-06 · Solar Benchmark
How Much Should a 6kW Solar System Produce Per Month?
A 6kW solar system produces between 500 and 900 kWh per month, depending on your location, roof orientation, and shading. The US national average is roughly 675 kWh/month — or about 8,100 kWh per year. If your system is consistently producing below 500 kWh/month in summer, that gap is worth investigating.
Monthly Production Benchmarks for a 6kW System
The table below shows expected monthly production for a 6kW system on a south-facing roof with a 30-degree tilt — the standard reference configuration for physics-based modeling. Numbers derived from pvlib simulation using Open-Meteo ERA5 historical weather data, averaged across US continental latitudes.
| Month | Expected Production (kWh) | Notes |
|---|---|---|
| January | 405 | Shortest days, lowest sun angle |
| February | 527 | Rapid improvement from Jan |
| March | 689 | Spring shoulder season begins |
| April | 770 | Strong production resumes |
| May | 851 | Near-peak month |
| June | 891 | Peak production month |
| July | 851 | Slightly lower than June (heat losses) |
| August | 810 | Heat losses ease late month |
| September | 729 | Rapid daylight reduction |
| October | 608 | Fall shoulder season |
| November | 486 | Sharp drop |
| December | 405 | Lowest month |
| Annual Total | ~8,100 | US national average |
(Source: pvlib physics modeling, Open-Meteo ERA5 weather data)
What These Numbers Mean
The monthly figures above represent what a well-functioning 6kW system should produce under real historical weather conditions — not a theoretical "typical year." That distinction matters. PVWatts, the most commonly cited free tool, uses Typical Meteorological Year (TMY) data, which averages out actual weather variability. In practice, PVWatts estimates deviate from measured production by roughly 38% in any given year. Physics-based models using ERA5 hourly weather data achieve 5–7% monthly deviation from measured performance.
If your monitoring app shows production 15% or more below these benchmarks for two consecutive months, something other than weather is likely responsible.
Regional Variation: 6kW System Annual Production
Your location has more impact on production than almost any other variable. The same 6kW system installed in Phoenix produces nearly twice what it produces in Seattle.
| Region | Example States | Annual kWh | Monthly Average |
|---|---|---|---|
| Southwest Desert | AZ, NV, inland CA | 10,800 | 900 |
| California Coast | coastal CA | 9,600 | 800 |
| Southeast | FL, TX, GA | 9,000 | 750 |
| Mid-Atlantic | NJ, MD, VA, NC | 8,100 | 675 |
| Midwest | OH, IL, MO | 7,500 | 625 |
| New England | MA, NY, CT | 6,900 | 575 |
| Pacific Northwest | WA, OR | 6,300 | 525 |
(Source: pvlib physics modeling, Open-Meteo ERA5 weather data, averaged 2015–2024)
What Affects a 6kW System's Output
- Roof orientation: A south-facing 6kW system at 30-degree tilt produces 100% of potential. West-facing produces about 87%. East-facing about 85%. North-facing drops to roughly 60% — rarely installed for that reason.
- Tilt angle: Flat roofs (0-degree) lose about 10% compared to an optimally tilted surface. Steeper than 45 degrees also reduces output, by 3–5%.
- Shading: Even partial shading of one panel cascades through string inverter systems. A 10% shaded area can reduce total output by 20–40% depending on inverter type.
- Temperature: Solar panels lose about 0.3–0.5% output per degree Celsius above 25°C. July in Phoenix regularly pushes panels to 60°C or higher, which is why June often outproduces July despite more daylight hours.
- Soiling: Dust, pollen and bird droppings reduce output by 1–5% in most US climates. California's dry season can push soiling losses above 5% without rainfall cleaning.
- Degradation: Expect about 0.5% annual output loss in PERC panels, and under 0.3%/year in TOPCon modules (2023+). A 6kW system that produced 8,100 kWh in year one should produce about 7,696 kWh by year 10.
Frequently Asked Questions
Q: My 6kW system only produced 520 kWh last month. Is that normal?
A: It depends on the month and your location. 520 kWh in January in New England is above average. 520 kWh in June in Texas is roughly 40% below what you should expect, which signals a real problem. Compare your production to the monthly benchmark for your specific region before concluding anything.
Q: How does a 6kW system compare to PVWatts estimates?
A: PVWatts provides a useful ballpark, but it uses Typical Meteorological Year data, which can diverge from actual weather by 20–40% in any given month. A 6kW system that PVWatts estimates at 700 kWh/month might actually produce 780 kWh in a sunny year or 620 kWh in a cloudy one. Physics-based models using ERA5 actual historical weather data reduce that error to 5–7%.
Q: Will a 6kW system cover a typical US household's electricity needs?
A: A typical US household uses about 10,500 kWh/year. A 6kW system producing 8,100 kWh/year covers roughly 77% of that load on average. Coverage varies significantly by climate and household consumption.
Q: What should I do if my 6kW system is consistently underproducing?
A: Start by pulling 12 months of production data from your monitoring app. Compare each month to the regional benchmarks above. If you see a 15% or greater gap for multiple months, request a site inspection. Document the shortfall with actual numbers before contacting your installer.
Data: pvlib physics modeling + Open-Meteo ERA5 weather data | Last updated: 2026-04-06 | Solar Benchmark