How many solar panels do I need in Puerto Rico?
Found by running the engine, not by dividing · 2026-09-11
The answer that circulates — divide your consumption by the sun hours — answers an easier question than the one you are asking. Covering a clear day is cheap. What decides whether the system disappoints you is the overcast day, and for the same house that is 2.6 times more panels.
Panels to cover the day, in Valle central
The smallest number of panels where the day produces at least what the day consumes. Same three houses as the days-with-no-grid page, so the two tables can be read together.
| The house | Clear day | Overcast day |
|---|---|---|
| The essentials 6.6 kWh a day |
3 1.75 kW |
8 4.68 kW |
| With one A/C at night 12 kWh a day |
5 2.92 kW |
13 7.61 kW |
| How people actually live 32.8 kWh a day |
12 7.02 kW |
30 17.55 kW |
This is production against consumption over a day, which is the question net metering asks. Whether it carries you through the night is a different question and it is answered by the battery — that is the other page.
Why the overcast column is so much bigger
An overcast sky in Puerto Rico leaves roughly a third of the irradiance of a clear one. The panel does not care that you paid for it: it harvests what arrives. So a system sized for the good day runs a deficit on every bad one, and the deficit comes out of the battery — which is exactly why people who sized with the napkin formula end up starting the generator.
The extra panel does eventually stop helping, but far later than people say: on this 12 kW inverter clipping does not start until 36 panels — 21 kW of glass on a 12 kW inverter — and even there it costs under 3 kWh on the day. Within any sane range, the panel you add delivers its full share. The engine accounts for the clipping; a division cannot.
Where you live moves it less than you would think
Between the best sun on the island and the mountain there is a 16 % spread in harvest, but panels come in whole numbers: for the small house that is one panel of difference, and for the big one two. Your town matters — it just matters less than what you leave running. The peak sun hours of all 78 municipalities are on the sun by town page, with the sources.
Work out yours, appliance by appliance →
Free, no card and no sign-up. Your consumption hour by hour, your town, your roof pitch, and what the inverter can actually take.
Worked out with 585 W panels and a 12 kW hybrid inverter, a 17° roof facing south, and the losses the simulator applies hour by hour: heat on the panel, dust, wiring and the inverter's own consumption. «Covers the day» means the day's production reaches the day's consumption — not that every hour is covered as it happens. Your own number will differ with your roof, your shade and your equipment.