How Much Power Does a 620W Solar Panel Produce in Lagos?

A 620W panel almost never makes 620W. In Lagos it peaks at about 459W around 1pm and produces about 2.4 kWh on an average day, 866 kWh a year. These figures come from InfraSol Intelligence, our solar model, which uses the output we measured every five minutes on a 74kWp array we installed in Lagos, scaled down to one panel.

Hour by hour

On a best day the panel is making useful power from about 8am to 5pm, and more than two-thirds of the day’s energy comes between 10am and 3pm. That is why solar homes run the washing machine, pumping and ironing around midday, and why the battery should be full by mid-afternoon.

Why it doesn’t make 620W

The 620W on the label is measured in a lab: full overhead sun and the panel held at 25°C. On a Lagos roof the panel runs at 50°C or more, and every degree above 25°C costs about 0.3% of its output. The sun is only straight overhead for part of the day, and wiring and the inverter take a few percent more. Our figures are what is left after all of that.

Good days and bad days

Lagos has about 184 best days a year, when one panel makes 2.92 kWh. On a poor day it makes 0.92 kWh, and on the 14 worst days only 0.63 kWh, about a fifth of a best day. A panel still works under cloud, just at a fraction of its output.

Month by month

January is the best month at 2.73 kWh a day; July, in the peak rains, is the worst at 1.89 kWh, about 31% less. June to September all average around 2 kWh a day. Size a system for those months, not the yearly average, or it will fall short every rainy season.

What one panel’s output can run

An average day’s 2.4 kWh is roughly a fridge-freezer for a day (most use 1 to 1.5 kWh) plus lights, fans and a TV, or about three hours of a 1HP inverter air conditioner once the room is cool. Power stored in a lithium battery for the night comes back at about 88%, so the same day’s output gives about 2.1 kWh after dark.

The full method, with batteries and inverter sizes, is in how many solar panels and batteries for your inverter.

What a year of one panel is worth

One panel’s 866 kWh a year would cost about ₦555,000 in diesel alone from a 10kVA generator, at about ₦640 of fuel per kWh. A 620W panel costs about ₦130,000 (₦134,000 from us), so if its output replaces generator power it pays for itself within a few months. A whole system takes longer, because the battery and inverter cost more than the panels, and power is wasted on days the battery is already full.

Bifacial panels can do a little better

The figures above leave out the back face of a bifacial panel like the Jinko Tiger Neo 620W, which also collects light bouncing up from below. How much it adds depends on the mounting: a few percent on a sloping roof, more when the panel is raised high over a light-coloured roof or ground. Treat it as a bonus, not something to size on. What panels of every size cost is in solar panel prices in Nigeria.