Peak Sun Hours in Louisville, Kentucky, United States
- Solar zone
- Zone 3 (good)
- Best month
- June (6.3)
- Worst month
- December (1.7)
- Climate
- Temperate · 12.6°C
Monthly solar breakdown
| Month | GHI | Clear-sky | DNI | DHI | Temp °C | Humid % |
|---|---|---|---|---|---|---|
| Jan | 1.92 | 3.13 | 2.65 | 0.95 | -0.7 | 85 |
| Feb | 2.64 | 4.24 | 2.97 | 1.29 | 0.7 | 85 |
| Mar | 3.69 | 5.61 | 3.53 | 1.70 | 6.4 | 82 |
| Apr | 4.96 | 6.92 | 4.35 | 2.08 | 12.8 | 79 |
| May | 5.53 | 7.64 | 3.98 | 2.64 | 18.1 | 81 |
| Jun | 6.30 | 7.92 | 4.87 | 2.67 | 22.6 | 79 |
| Jul | 6.04 | 7.61 | 4.61 | 2.60 | 24.5 | 77 |
| Aug | 5.53 | 6.87 | 4.49 | 2.36 | 24.4 | 71 |
| Sep | 4.60 | 5.83 | 4.72 | 1.75 | 20.8 | 69 |
| Oct | 3.33 | 4.53 | 4.25 | 1.25 | 13.6 | 73 |
| Nov | 2.33 | 3.33 | 3.47 | 0.96 | 6.7 | 79 |
| Dec | 1.67 | 2.76 | 2.47 | 0.82 | 1.5 | 86 |
GHI, Clear-sky, DNI, DHI in kWh/m²/day. Data: NASA POWER climatology (long-term monthly averages).
Off-grid calculator
Add appliances
- Add an appliance to size a system.
Sizing
- Daily load
- 0.00 kWh
- Panel wattage
- 0 W
- Panel count (400W modules)
- 0
- Battery bank
- 0.0 kWh
Sizing against worst-month PSH of 1.67 kWh/m²/day, 0.77 system efficiency.
About solar in Louisville
Louisville, United States has a temperate climate with meaningful seasonal variation in solar resource. Its annual peak sun hours average 4.05 kWh/m²/day, a good solar resource by global standards.
The strongest month in Louisville is June (summer) at 6.3 kWh/m²/day, and the weakest is December (winter) at 1.67 kWh/m²/day. When sizing a year-round off-grid system, it's standard practice to design against the December value rather than the annual average — otherwise the battery bank runs low during the darkest weeks.
Louisville's solar conditions are well within the range where off-grid PV is a straightforward engineering exercise with standard-sized arrays and lithium batteries.
FAQ
- What are the peak sun hours in Louisville?
- Louisville averages 4.05 peak sun hours per day annually, ranging from 1.67 in December to 6.3 in June.
- How many solar panels do I need in Louisville?
- Panel count depends on your daily load. At Louisville's annual average of 4.05 kWh/m²/day, a 5 kWh/day load needs roughly 5 × 400 W panels. Use the calculator above for your actual load.
- What size battery do I need in Louisville?
- Sizing against Louisville's worst month (December, 1.67 kWh/m²/day) with 2 days of autonomy at 80% depth of discharge, a 5 kWh/day load needs about a 12.5 kWh battery bank.
- How does Louisville's solar resource compare globally?
- Louisville sits in solar zone 3 out of 5 (where 5 is strongest) at 4.05 kWh/m²/day — good by global standards. For reference, top-tier desert sites average ~6.5 and high-latitude cities around 2.5 kWh/m²/day.
- How much does winter reduce solar output in Louisville?
- Louisville's worst month (December) delivers 1.67 kWh/m²/day — about 27% of the summer peak of 6.3. Off-grid systems here typically oversize 1.5–2× or pair with a backup source.
- Do cloudy days significantly affect Louisville's solar?
- Partly. Diffuse light still produces 10–25% of clear-sky output. Louisville's 4.05 kWh/m²/day already reflects average cloudiness, so no further derating is needed for sizing.
- What panel tilt works best in Louisville?
- At Louisville's latitude (38°), a fixed tilt near 38° balances year-round yield. Winter-heavy loads favor latitude + 15°; summer-heavy, latitude − 15°.