Guide · Sizing
How many panels and what power?
The question comes up at every first contact: "how many panels do I need?". The answer isn't read off a panel, it's read off a bill. Let's take a real one and follow it through to the number of modules. Our example: a Casablanca villa whose Lydec reading shows 6,000 kWh over the year. We'll work back from that figure to the power to install, then to the number of panels.
Step 1 — find the kWh on your bill
The starting data point is annual consumption in kilowatt-hours (kWh). It appears on the ONEE bi-monthly reading, or in your distributor's customer portal: Lydec in Casablanca, Redal in Rabat, Amendis in Tangier. The reflex is to add up the year's six bi-monthly readings, or multiply the average bi-monthly reading by six. For our villa, the sum of readings gives 6,000 kWh — it's this figure, read off the paper, that drives everything else.
Without readings on hand — a new house, a first installation — you estimate from the big loads: air conditioners, water heaters, appliances, lighting. A Moroccan villa with air conditioning commonly runs between 4,000 and 10,000 kWh a year, but that's a range, not an average to copy. Start from your real numbers.
Step 2 — go from kWh to kWc
You divide annual consumption by the expected output of one kWc in your region. In Morocco, the benchmark is 1,500 to 1,800 kWh produced per kWc installed per year depending on the zone, or about 5 to 5.5 hours of useful sunshine a day on annual average (source: PVGIS / Global Solar Atlas).
Applied to our villa: 6,000 kWh divided by about 1,600 kWh/kWc gives roughly 4 kWc. More broadly, consumption of 4,000 to 6,000 kWh/year points to 3 to 5 kWc, and 6,000 to 10,000 kWh/year to 5 to 8 kWc. These are benchmarks: roof orientation, shading, the targeted self-consumption rate, and Law 82-21's 20 % injection cap shift the result one way or the other.
Step 3 — from kWc to number of panels
The modules we install today are high-power panels of about 700 Wc (Canadian Solar and Jinko at 710 Wc, monocrystalline). At this power, one kWc corresponds to about 1.4 to 1.5 panels: seven 710 Wc modules make roughly 5 kWc. Our 4 kWc villa therefore fits in 6 panels; a 5 kWc installation needs 7, a 3 kWc one needs 4 to 5.
On the roof, each panel takes up about 3.1 m² (710 Wc module, 2,384 × 1,303 mm), which always comes back to the same area benchmark, around 4.3 to 4.4 m² of roof per kWc installed: the rise in module power reduces their number, not the total space they take up. Our 4 kWc villa thus needs on the order of 17 to 18 m² of clear, well-oriented, unshaded surface.
Where your bill isn't enough anymore
This bill → kWc → panels path gives a reliable order of magnitude, and that's exactly what it's for. But it stops at your roof's door. Real orientation and tilt move production: a flat roof facing north and a south-facing pitched one don't give the same kWh per kWc. Your targeted self-consumption rate also shifts the optimal size — covering 80 % of your consumption doesn't call for the same installation as covering 60 %. And the 20 % injection cap means that beyond a certain point, adding panels no longer translates into value.
That's where an on-site survey takes over: we start from your real readings, measure orientation and obstructions, and produce the exact sizing — kWc, number of panels, surface area — for your house rather than the example villa.