Peak Sun Hours in Cardiff, Wales, United Kingdom
- Solar zone
- Zone 1 (modest)
- Best month
- June (5.3)
- Worst month
- December (0.6)
- Climate
- Temperate · 10.3°C
Monthly solar breakdown
| Month | GHI | Clear-sky | DNI | DHI | Temp °C | Humid % |
|---|---|---|---|---|---|---|
| Jan | 0.80 | 1.45 | 1.70 | 0.43 | 5.1 | 93 |
| Feb | 1.49 | 2.59 | 2.35 | 0.78 | 4.9 | 91 |
| Mar | 2.66 | 4.26 | 2.94 | 1.41 | 6.2 | 89 |
| Apr | 4.11 | 6.11 | 3.79 | 2.06 | 8.7 | 85 |
| May | 5.02 | 7.57 | 4.19 | 2.49 | 11.7 | 83 |
| Jun | 5.32 | 8.13 | 4.11 | 2.69 | 14.7 | 82 |
| Jul | 5.04 | 7.73 | 3.95 | 2.54 | 16.4 | 82 |
| Aug | 4.16 | 6.49 | 3.38 | 2.22 | 16.3 | 84 |
| Sep | 3.22 | 4.80 | 3.36 | 1.65 | 14.4 | 85 |
| Oct | 1.81 | 3.02 | 2.39 | 0.97 | 11.4 | 89 |
| Nov | 0.96 | 1.70 | 1.82 | 0.52 | 8.1 | 92 |
| Dec | 0.62 | 1.14 | 1.50 | 0.34 | 5.9 | 93 |
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 0.62 kWh/m²/day, 0.77 system efficiency.
About solar in Cardiff
Cardiff, United Kingdom has a temperate climate with meaningful seasonal variation in solar resource. Its annual peak sun hours average 2.93 kWh/m²/day, a modest solar resource by global standards.
The strongest month in Cardiff is June (summer) at 5.32 kWh/m²/day, and the weakest is December (winter) at 0.62 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.
Given the modest resource, Cardiff installations typically oversize panels or combine solar with another source (grid, generator, hydro) for reliability.
FAQ
- What are the peak sun hours in Cardiff?
- Cardiff averages 2.93 peak sun hours per day annually, ranging from 0.62 in December to 5.32 in June.
- How many solar panels do I need in Cardiff?
- Panel count depends on your daily load. At Cardiff's annual average of 2.93 kWh/m²/day, a 5 kWh/day load needs roughly 6 × 400 W panels. Use the calculator above for your actual load.
- What size battery do I need in Cardiff?
- Sizing against Cardiff's worst month (December, 0.62 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 Cardiff's solar resource compare globally?
- Cardiff sits in solar zone 1 out of 5 (where 5 is strongest) at 2.93 kWh/m²/day — modest 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 Cardiff?
- Cardiff's worst month (December) delivers 0.62 kWh/m²/day — about 12% of the summer peak of 5.32. Off-grid systems here typically oversize 1.5–2× or pair with a backup source.
- Do cloudy days significantly affect Cardiff's solar?
- Partly. Diffuse light still produces 10–25% of clear-sky output. Cardiff's 2.93 kWh/m²/day already reflects average cloudiness, so no further derating is needed for sizing.
- What panel tilt works best in Cardiff?
- At Cardiff's latitude (51°), a fixed tilt near 51° balances year-round yield. Winter-heavy loads favor latitude + 15°; summer-heavy, latitude − 15°.