Sizing an off-grid solar system on Sal, Cape Verde

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How many solar panels and how large a battery does a house on Sal (Cape Verde, Cabo Verde) need to run fully off-grid? You can make a good first estimate yourself in six steps. Below each step you find a worked example for a house in Santa Maria.

Step 1: list your consumption per day

Write down every appliance with its power in watts and the hours it runs per day. Watts times hours gives watt hours; add them up and divide by 1,000 for kilowatt hours (kWh) per day. The label on the appliance or your electricity bill helps. Example: the house uses 12 kWh per day.

Step 2: split day and night

Everything you use after sunset must come from the battery. Example: 5 kWh during the day, 7 kWh in the evening and at night.

Step 3: the solar array

Divide the daily consumption by the effective sun hours and by the efficiency of the system. For Sal we use a careful 5 effective sun hours and about 20 percent losses for heat, dust, cabling and charging. Example: 12 kWh ÷ 5 ÷ 0.8 = 3 kWp. With a margin for hazy days we would advise around 4 kWp.

Step 4: the battery

Multiply the night consumption by the number of days the house must run without useful sun (the autonomy), and divide by the usable share of the battery. A lithium iron phosphate (LiFePO4) battery can use about 90 percent of its capacity. Example: 7 kWh × 1.5 days ÷ 0.9 ≈ 12 kWh of battery capacity. On Sal one to two days of autonomy is usually enough; a generator input covers the rare longer period of Saharan dust.

Step 5: the inverter

Add up everything that can run at the same time and check the starting current of motors such as pumps and air conditioners. Example: two air conditioners, a water pump and the kitchen together need around 5 kW continuous power, with extra surge capacity for starting.

Step 6: check the details

• Is there enough roof or ground space without shade, also in winter when the sun is lower?
• Can the frames handle the trade wind, and is the mounting corrosion resistant?
• Is there a shaded, ventilated place for the battery and inverter?

These figures are an example with assumptions, not a quote. Every house is different, and a small change in night consumption changes the battery a lot. See also what an off-grid system costs.

Let Huefter calculate it exactly

Send us your appliances or your electricity bills and we calculate the exact system for your house in Santa Maria, Murdeira, Espargos, Palmeira or elsewhere on Sal. Back to off-grid solar on Sal, or send us a message on WhatsApp: +238 597 56 78.