Solar Traffic Light Panel Wattage and Tilt Angle Selection
Introduction
A solar traffic signal needs a panel sized for the worst-case month at the site latitude. Under-size and the battery dies in winter; over-size and you pay for capacity you don't need. This guide covers the calculations.
Peak Sun Hours
Peak sun hours (PSH) is the average daily solar irradiance in equivalent hours at 1000 W/m². For a fixed-tilt panel, use the local December (worst-case) PSH:
- Tropical (lat < 23.5°): 4.5-5.5 PSH in winter
- Mid-latitude (lat 30-45°): 2.5-3.5 PSH in winter
- High-latitude (lat > 45°): 1.5-2.5 PSH in winter
GAOQIAO uses NASA POWER or PVGIS data for site-specific PSH calculations.
Panel Wattage Calculation
Panel wattage = (daily load Wh × autonomy days) / (PSH × derate)
For a 200 Wh/day load, 3-day autonomy, 3.0 PSH, 0.7 derate:
Panel wattage = (200 × 3) / (3.0 × 0.7) = 600 / 2.1 = 286 W
Round up to a standard panel size: 300 W or 350 W. GAOQIAO standard solar traffic signals use 200-400 W panels.
Tilt Angle by Latitude
Tilt the panel at the site latitude for year-round average performance, or at latitude + 15° for winter optimisation. Higher latitudes benefit from steeper winter tilt:
- Latitude 0-10°: tilt 10-15°
- Latitude 10-30°: tilt = latitude
- Latitude 30-50°: tilt = latitude + 5° for winter optimisation
- Latitude > 50°: tilt = latitude + 10° for winter optimisation
GAOQIAO supplies adjustable mounting brackets for sites where the optimal tilt differs from the pole or cabinet mounting angle.
Panel Type and Degradation
Monocrystalline panels are the standard for solar traffic signals. They have:
- Higher efficiency (20%+) so smaller panel area for the same wattage
- Better low-light performance (important in winter)
- Lower degradation rate (0.5% per year)
Polycrystalline panels are cheaper but larger and less efficient. GAOQIAO standard panels are monocrystalline with 25-year power warranties.
Featured Products
GAOQIAO supplies solar traffic signals with matched panel sizing. See the solar site survey guide.
Conclusion
Right-size the panel for the worst-case month at your latitude. GAOQIAO supplies sized panels with mounting brackets and tilt recommendations. Send us your location and load profile for a sizing worksheet.
Get a Quote
Email: sky-sale@njgq.net WhatsApp/Phone: +86-18805173545 Tel: +86-25-84471080
Frequently Asked Questions
What tilt angle should I use for my latitude?
Tilt = latitude for year-round average, latitude + 10° for winter optimisation. GAOQIAO uses latitude-based defaults unless you specify otherwise.
Should the panel face true south?
In the northern hemisphere yes (true south, not magnetic). In the southern hemisphere, face true north. The panel should never face east or west as the primary direction.
Can I use a bifacial panel?
Bifacial panels can produce 10-20% more energy but require ground reflection. GAOQIAO uses bifacial panels for ground-mount solar traffic signals on light-coloured ground.
Relevant GAOQIAO products
These public GAOQIAO catalogue pages are related to the guide. Open them for the representative description, then confirm the latest drawing and configuration before ordering.
- Traffic signal controllersWired and solar controllers with 6, 22, 44 and 56 output options.
- LED traffic signal heads200mm, 300mm and 400mm signal heads with MUTCD, EN12368, GB14886 compliance.
- Signal polesVertical, signal arm and double-arm poles for any intersection geometry.
- Spare parts and accessoriesSpare LED modules, lenses, visors, surge arrestors and anchor bolts.