When considering the installation of a solar power system, one of the most crucial steps is determining the appropriate size for your needs.
The size of the solar system you need depends on several factors, including your energy consumption, available roof space, and budget. The size of the system directly impacts its efficiency and your overall energy savings. At OG Electrical Services we are here to help you navigate this seemingly difficult exercise. Below we are giving you a step-by-step guide to help you determine the perfect solar system size for your needs.
Steps to Calculate Your Solar System Size
1. Assess Your Energy Usage
Begin by evaluating your average daily energy consumption. The first step is to understand how much electricity your household or business uses. You can find this information on your utility bills, usually expressed in kilowatt-hours (kWh). To get an accurate picture, consider collecting data from your last 12 months of bills. Take note of:
- Your average monthly electricity usage.
- Seasonal variations, especially if you use heating or cooling systems extensively.
For example, if your home uses 900 kWh per month, your daily consumption would be approximately 30 kWh (900 kWh / 30 days).
2. Consider Sunlight Availability
Next, identify the average number of peak sun hours in your area. Peak sun hours refer to the hours during which sunlight is strong enough to generate electricity effectively. This varies by location and season; for instance, areas with more sunshine will have higher peak sun hours. You can typically find this information through local weather services or solar energy resources
The amount of sunlight your location receives affects how much energy your solar panels can generate. Johannesburg, for example, enjoys abundant sunshine, averaging around 5 to 6 hours of peak sunlight daily. Multiply your daily energy consumption by a factor to account for sunlight hours:
3. Calculate Your Solar System Size
With your daily kWh usage and peak sun hours in hand, you can now calculate the size of your solar system using the following formula:
- Daily Energy Use (kWh) ÷ Peak Sunlight Hours = Required System Size (kW)
If your home uses 30 kWh daily and you get 5.5 hours of sunlight, you’d need a system size of approximately 5.45 kW (30 kWh ÷ 5.5 hours).
4. Determine the Number of Panels Needed
To find out how many solar panels you will need, divide your calculated system size by the wattage of the solar panels you plan to use. Most modern panels range from 250W to 400W each. If you choose a panel rated at 400W, the calculation would be:
Number of Panels=System Size W Panel Output W Number of Panels=Panel Output W System Size W
Continuing with our example:
Number of Panels=7200400=18 panels Number of Panels=4007200=18 panels
Solar panels and inverters are not 100% efficient. Most systems operate at 80-90% efficiency due to factors like shading, temperature, and inverter losses. To account for this, increase the system size by 10-20%:
- Required System Size × Efficiency Factor = Adjusted System Size
Using the earlier example, a 5.45 kW system with 85% efficiency would require an adjusted size of about 6.4 kW (5.45 kW × 1.15).
4. Check Roof Space and Orientation
Your roof’s size, orientation, and angle will determine how many panels you can install. A typical solar panel produces 300-450 watts and requires around 1.7 m² of space. For a 6.4 kW system using 400W panels, you’d need approximately 16 panels and 27.2 m² of roof space.
Panels should ideally face north in the southern hemisphere for maximum efficiency.
5. Consider Future Energy Needs
As you size your solar system, think about potential future increases in energy consumption, such as purchasing electric vehicles or adding new appliances. It may be wise to size up slightly to accommodate these changes without needing a complete system overhaul later.
6. Budget Considerations
Solar system costs vary depending on the size, brand, and quality of components. Here’s a rough estimate for installed systems:
- Small (3-5 kW): ZAR 50,000 – ZAR 100,000
- Medium (5-10 kW): ZAR 100,000 – ZAR 200,000
- Large (10+ kW): ZAR 200,000+
Remember to factor in potential government rebates or incentives.
7. Include Battery Storage (Optional)
If you want to store excess energy for nighttime use or during power outages, consider adding a battery system. The size of your battery will depend on your backup needs. A typical home might require a 5-10 kWh battery.
8. Consult with OG Electrical Services
While these calculations provide a solid foundation for sizing your solar system, we suggest that you contact us at OG Electrical Services for consultation and a proposal on the perfect size system that will meet your needs and is tailored to your unique situation.
The number to use is +27 73 378 6966 and email info@ogelectrical.co.za
Read more about our Solar Power System solutions on the following link https://www.ogelectrical.co.za/solar-power-installations/