How to Properly Size a Solar System for Your Home in South Africa

Choosing the right solar system size for your home is crucial for energy efficiency, cost savings, and uninterrupted power during load shedding. A solar system that’s too small won’t meet your needs, while one that’s too large could result in wasted investment.

In this guide, we explain how to accurately size a solar system based on your energy usage, roof space, location, and backup requirements.

🔌 Step 1: Understand Your Electricity Consumption

Start by reviewing your electricity bill to find your average monthly usage in kilowatt-hours (kWh).

Example:

• Average household consumption: 600–900 kWh/month

• Daily usage: 20–30 kWh/day

Check your bill for:

• Daily average kWh

• Monthly peak usage

• Seasonal fluctuations (heaters or ACs)

📊 Step 2: Estimate Daily Solar Needs

To size your system, you need to estimate how much solar energy you want to generate per day.

Formula:
Solar system size (kW) = Daily kWh needed ÷ Average peak sun hours

Example (Johannesburg):

• 30 kWh/day ÷ 5.5 sun hours ≈ 5.5 kW system

🌍 South Africa averages 4.5–6.5 sun hours/day depending on location.

🧱 Step 3: Consider Backup Requirements

Decide if you want a grid-tied, hybrid, or off-grid system:

For load shedding, calculate your critical load:

• Lights, fridge, Wi-Fi, TV, plugs for chargers, etc.

• Usually around 1–2.5 kW per hour of backup needed

🔋 Step 4: Select the Right Battery Size (if needed)

Batteries store energy for use during power cuts or at night.

Common residential sizes:

• 3.5 kWh = essential backup only

• 5.1 kWh = medium backup + longer runtime

• 10+ kWh = full home backup

Lithium-ion batteries are preferred for lifespan and efficiency.

⚡ Step 5: Choose Your Inverter Capacity

Your inverter size should match or slightly exceed your system size.

• 5kW solar = 5kW inverter (or hybrid inverter)

• Add 20% margin if future expansion is planned

• Check for inverter compatibility with battery if hybrid

📐 Step 6: Check Your Roof Space

Each 550W solar panel is approx. 2m² in size.
A 5kW system needs 9–10 panels → 18–20m² of roof space.

✅ Ensure your roof:

• Faces north or northwest for optimal exposure

• Has minimal shading

• Is strong enough to support mounting structure

🧮 Sample Solar System Sizing Scenarios

🛠 Bonus Tips for Accurate Sizing

• Install a smart meter for live usage data

• Account for future loads (EVs, new appliances)

• Factor in seasonal variations

• Allow 10–20% headroom for cloudy days

• Use certified solar installers for accurate assessment

🔗 Internal Links

• What is the Cost of Installing Solar Panels in South Africa?

• What Type of Inverter Do I Need for a Hybrid System?

• What is the Best Battery Backup for Solar Power?

📝 Final Thoughts

Sizing a solar system isn’t just about panel count—it’s about matching your energy needs, budget, and backup goals. Work with a reputable solar installer like Africa Power Equipment to analyse your consumption and customise a system that ensures savings, energy independence, and peace of mind.