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Solar and backup power in San Juan
San Juan gets 5.22 peak sun hours a day on average. The dullest month is December at 4.08 hours, 31% less than April, the sunniest at 5.93. That makes it sunnier than 0% of the 6 cities we cover in Puerto Rico.
Sunshine in San Juan is clearly below its yearly average for 3 months, from November to January. That stretch decides how many panels you need if solar has to keep up all year. Across the year, San Juan gets 4% less sunshine than the average of the cities we cover in Puerto Rico.
What a home in San Juan needs
Three example homes, each covering a 12-hour daily outage with a lithium battery and solar panels to recharge it. Panels are 450 W. The month-with-least-sun figure is what keeps you covered all year.
| Home | Inverter | Battery | Panels, December | Panels, yearly average |
|---|---|---|---|---|
| Essentials 6 lights, 2 fans, a fridge, TV, Wi-Fi and phone charging | 1 kW | 2.6 kWh | 2 | 2 |
| Family home Essentials plus a freezer, more lights, a laptop, a desktop and a water pump | 3 kW | 7.4 kWh | 5 | 4 |
| With air conditioning The family home plus two small air conditioners for 6 hours a day | 5 kW | 14.9 kWh | 9 | 7 |
Your own appliances will differ. Put them into the calculator below, which already has San Juan's sunshine.
Size your own system in San Juan
Planning tips for San Juan
- Size panels for December, not for the yearly average. A system sized on the average falls short in the dullest weeks, which is when you most need it.
- Dust, heat and shade cut output. Keep panels clean, leave air space under them, and avoid anything that shades them between mid-morning and mid-afternoon.
- Ask installers for the inverter's continuous and surge ratings, the battery's usable capacity and chemistry, and the panels' total watts. Compare those numbers with your plan rather than the package name.
Guides for planning in San Juan
- Peak sun hours and your dullest month
- How many solar panels you need
- Lithium vs lead-acid batteries
- Questions to ask an installer
Nearby cities
- Fajardo 50 km · 5.53 h
- Guayama 54 km · 5.76 h
- Arecibo 64 km · 5.22 h
- Ponce 75 km · 5.22 h
- Mayagüez 113 km · 5.58 h
Sunshine: NASA POWER climatology, ALLSKY_SFC_SW_DWN, monthly averages for 25-year Meteorological and Solar Monthly & Annual Climatologies (January 2001 - December 2025), at 18.4663, -66.1057; retrieved 2026-11-09. Peak sun hours equal kWh of sunlight per square metre per day on flat ground; tilted panels usually collect a little more.