As load shedding and rising electricity costs affect South Africans, many homeowners and businesses turn to solar and battery backup systems to ensure uninterrupted power. However, choosing the right battery size for your solar energy storage system is crucial to maximising efficiency and cost-effectiveness.
Deltec Energy Solutions specialises in solar batteries and backup power solutions tailored to your energy needs. This guide will help you determine the best battery size for your home or business, ensuring you get the most out of your solar power system.
Why Battery Sizing Matters in a Solar System
A properly sized solar battery ensures:
- Reliable backup power during load shedding and grid failures
- Maximum energy efficiency by storing excess solar power
- Lower electricity bills by reducing reliance on Eskom
- Longer battery lifespan with optimal charge and discharge cycles
Step 1: Calculate Your Energy Consumption
The first step in sizing your solar battery system is determining how much electricity you use daily.
How to Calculate Your Daily Energy Needs
- Check your electricity bill – Look at your average monthly kWh usage and divide by 30 to get your daily consumption.
- List essential appliances – Identify critical loads you want to power during outages (e.g., lights, fridge, Wi-Fi, TV, computers, and security systems).
- Calculate total wattage – Multiply each appliance’s wattage by the daily hours used
For example:
| Appliance | Power (W) | Hours Per Day | Total Energy (Wh) |
| Fridge | 150W | 24 hrs | 3,600 Wh |
| Wi-Fi | 15W | 10 hrs | 150 Wh |
| Lights | 50W | 6 hrs | 300 Wh |
| TV | 100W | 4 hrs | 400 Wh |
| Laptop | 60W | 5 hrs | 300 Wh |
| Total | 4,750 Wh (4.75 kWh) |
Step 2: Choose the Right Battery Size
How to Determine Your Battery Capacity
- Battery storage is measured in kilowatt-hours (kWh). To find the right size:
- Take your daily energy consumption (from Step 1).
- Decide how many backup hours you need.
- Factor in the depth of discharge (DoD) – most batteries should not be discharged 100%.
Battery Size Calculation Formula:
Battery Capacity (kWh) = Total Daily Usage (kWh) × Backup Hours ÷ Depth of Discharge (DoD)
For a 4.75 kWh daily load, needing 6 hours of backup with a lithium battery (DoD 90%):
Battery Capacity = (4.75 kWh × 6) ÷ 0.9 = 31.67 kWh
Recommended Battery Sizes
| System Type | Battery Size (kWh) | Best For |
| Small Home | 5-10 kWh | Essential backup (lights, Wi-Fi, TV) |
| Medium Home | 10-15 kWh | Multiple appliances, fridge, security |
| Large Home | 15-20 kWh | Full-house backup (including geyser, stove) |
| Small Business | 20-30 kWh | Office equipment, POS systems, lighting |
| Large Business | 30+ kWh | Industrial or commercial operations |
Step 3: Choose the Right Battery Type
1. Lithium-ion batteries (Best for Solar)
✅ Long lifespan (10-15 years)
✅ High efficiency (90%+ DoD)
✅ Fast charging and lightweight
❌ Higher upfront cost
2. AGM & Gel Batteries
✅ Lower upfront cost
✅ Maintenance-free
❌ Shorter lifespan (3-5 years)
❌ Lower efficiency and slower charging
3. Lead-Carbon & Tubular Batteries
✅ Better than traditional lead-acid
✅ Higher cycle life
✅ Good for deep discharge applications
❌ Bulkier and requires maintenance
Step 4: Select the Right Inverter
Your solar inverter must be compatible with your battery system. Consider:
- Pure sine wave inverters for better efficiency
- Hybrid inverters combine grid, solar, and battery power
- Scalability to allow future battery expansions
Conclusion: Get the Right Solar Battery System for Your Needs
Choosing the right battery size for solar and backup power is essential for reliability, cost savings, and system longevity. Whether you need a small home backup system or a large business energy storage solution, Deltec Energy Solutions has the expertise to guide you.
Contact Us Today!
🌐 Website: www.deltecenergysolutions.co.za
📞 Phone: 011 864 7930
📧 Email: sales@deltec.co.za
Power up with Deltec Energy – South Africa’s trusted solar experts!