Solar System Sizing Guide for Off-Grid Homes

Solar System Sizing Guide for Off-Grid Homes

“Will a 50W solar panel run my TV and fridge?” We hear this question almost every week. And the honest answer is: it depends on your TV, your fridge, and how many hours you use them.

Getting the size right matters more than most buyers realize. An undersized system leaves customers frustrated. An oversized one prices you out of the market. Here’s how to hit the sweet spot.

Step 1: Calculate Daily Energy Consumption

The golden rule of solar sizing: every system starts with what the user plugs into it.

Create a simple table of all appliances and their daily usage:

For a household without a refrigerator, total consumption typically falls around 300-400 Wh/day. With a refrigerator, expect 700-1,000 Wh/day.

Step 2: Size the Solar Panel Array

Here’s the simple formula:

Panel wattage = Daily energy consumption ÷ Peak sun hours ÷ System efficiency

In most of Africa, average peak sun hours range from 4.5 to 6 hours per day. Accounting for system losses (wire loss, battery charging loss, temperature), we use an efficiency factor of roughly 0.75.

Using the 821 Wh example above with 5 peak sun hours: 821 ÷ 5 ÷ 0.75 = 219W

So a 200W-250W panel array would be right for this household.

Step 3: Size the Battery Bank

Battery capacity (Ah) = Daily consumption ÷ Battery voltage × Days of autonomy ÷ Depth of discharge

For a 12V system with 1 day of autonomy and 50% depth of discharge (LiFePO4 batteries can handle deeper discharge): 821 ÷ 12 × 1 ÷ 0.5 = 137 Ah

A 150Ah LiFePO4 battery is the practical choice here.

A Quick Reference Table

For distributors who want a simple starting point:

This is where BESTWE’s ready-made solar home systems make life easier. Rather than piecing together components from different suppliers, you can order pre-matched systems where the panel, battery, controller, and wiring are already sized to work together. Our systems come in standardized tiers — Basic, Standard, and Premium — covering the most common African household configurations.

Step 4: Don’t Forget the Controller

The charge controller is the unsung hero of any solar system. For small systems, a PWM controller works fine. For anything above 100W, invest in an MPPT controller — it pulls 20-30% more energy from the same panel, especially in cloudy conditions or partial shade.

At BESTWE, all our systems above the Basic tier include MPPT controllers as standard. It’s a small component that makes a big difference in real-world performance.

The Golden Rules of Solar Sizing

Rule 1: Panel over battery — A slightly oversized panel is forgiving; an undersized one leaves batteries chronically undercharged.

Rule 2: Always add 20% — Real-world consumption is almost always higher than calculated. Account for it.

Rule 3: Plan for expansion — A system that lets the user add one more panel later is better than one that doesn’t.

The Bottom Line

Solar sizing doesn’t have to be complicated. Start with the appliances, calculate consumption, match the components. For experienced distributors, the formula above gives you everything you need. For those who want a turnkey solution, pre-packaged solar home systems save time and reduce configuration errors.

Need pricing or

Battery selection is critical to system sizing. Compare your options in our guide: LiFePO4 vs lead-acid batteries for off-grid solar.

help selecting the right system for your customers? Contact BESTWE at https://www.bestweenergy.com/contact-us/ for a wholesale price list and system recommendations.

Tags: solar system sizing guide for off grid home, smallest solar home system cost, solar home system factory price

For more information, check our guides on 12V vs 24V vs 48V off-grid solar, DC solar freezers, DC solar fans.

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