How to Size a Solar System for Your Home or Business

Thinking about going solar? That’s a smart move. But before you install solar panels, batteries, and an inverter, it’s crucial to size your solar system properly. Whether for a small home or a growing business, correct sizing ensures you get enough power without overspending.

In this guide, we’ll break down how to size a solar system step-by-step, so you get reliable, cost-effective energy tailored to your exact needs.

Why Proper Solar Sizing Matters

Installing a solar system that’s too small will leave you in the dark when you need it most. Go too big, and you’re paying for power you don’t use.

Proper solar sizing ensures:

• Uninterrupted power supply
  
  

• Maximum return on investment (ROI)
  
  

• Efficient use of solar panels and batteries
  
  

• Optimized energy savings over time
  
  

Step-by-Step: How to Size a Solar System

✅ Step 1: List Your Electrical Appliances

Make a list of the appliances you want to power with solar energy.

Example for a home:

• LED Bulbs (6 units) – 10W each
  
  

• Ceiling Fan (2 units) – 70W each
  
  

• Fridge – 150W
  
  

• TV – 100W
  
  

• Laptop – 50W
  
  

• Router – 20W
  
  

Example for a business (e.g., small office):

• Desktop Computers (4 units) – 150W each
  
  

• Printer – 100W
  
  

• Air Conditioner – 900W
  
  

• Lights (10 units) – 10W each
  
  

• Wi-Fi Router – 20W
  
  

✅ Step 2: Estimate Daily Usage (in Watt-hours)

Use this formula:
Wattage × Number of Hours Used per Day = Daily Consumption (Wh)

Example (Home TV):
100W × 4 hours = 400Wh/day

Do this for each appliance and total the values.

✅ Step 3: Add a Buffer (25–30%)

Add a buffer of about 25–30% to account for energy loss, inefficiencies, and cloudy days.

Total Daily Consumption × 1.3 = Final Required Load

✅ Step 4: Determine Battery Size

To calculate battery size, divide your total daily usage by the battery voltage (usually 12V or 24V):

Battery Size (Ah) = Total Load (Wh) / Battery Voltage

For example,
3000Wh ÷ 12V = 250Ah battery bank

Use lithium batteries for better efficiency and lifespan.

✅ Step 5: Calculate Solar Panel Capacity

Divide your daily energy requirement by the average daily sunlight hours (Nigeria averages 4–5 hours/day):

Solar Panel Size (W) = Daily Load (Wh) ÷ Peak Sunlight Hours

Example:
3000Wh ÷ 5 = 600W minimum (but go higher to allow for cloudy days)

We recommend at least 20–30% more capacity than your base need.

✅ Step 6: Choose the Right Inverter

Your inverter must match or exceed the total wattage of the appliances you’ll be running at the same time.

If your peak simultaneous load is 2000W, get a 2.5kVA or 3kVA inverter to avoid overload.

Read Also: How to choose the best solar inverter package

Read Also: A guide to selecting the right inverter size

Example: Sizing a Solar System for a 3-Bedroom Home

Let’s say your total daily power consumption is 4000Wh.

• Battery Bank Needed: 4000Wh ÷ 12V = ~334Ah
  
  

• Solar Panel Size: 4000Wh ÷ 5 hrs = 800W → Round up to 1000W
  
  

• Inverter Size: 2.5kVA to 3kVA (depending on simultaneous use)
  
  

At Solar Depot, we’d recommend a 3kVA solar package with a 100Ah–200Ah lithium battery bank and 4 x 250W panels for this setup.

Example: Sizing for a Small Office

If your office uses 6000Wh per day:

• Battery Bank: 6000Wh ÷ 24V = 250Ah
  
  

• Solar Panel Size: 6000Wh ÷ 5 = 1200W (use 1500W to be safe)
  
  

• Inverter Size: 3.5kVA–5kVA depending on peak load

Pro Tips for Sizing a Solar System

• Start small and expand: Use a modular system that allows you to add more panels or batteries as needed.
  
  

• Always consider future usage: Add 10–20% extra to accommodate more appliances in the future.
  
  

• Account for nighttime use: Make sure your battery bank can carry you through the night.
  
  

• Install efficient appliances: The lower your consumption, the smaller your system needs to be.
  
  

Why Solar Sizing Matters in Nigeria

In Nigeria, inconsistent grid power and high fuel costs make solar a vital investment. However, many users either oversize and waste money or undersize and still suffer outages. That’s why accurate solar sizing is essential.

Sizing a solar system might seem complicated, but it’s the key to unlocking clean, stable, and affordable power for your home or business. When done right, it ensures you get the best performance without overspending.

At Solar Depot Nigeria, we help you evaluate your needs and provide tailor-made solar packages with battery + inverter + panel combos that match your exact usage.

Ready to Go Solar?

Let our experts help you size your system and recommend the perfect package.