Transitioning to solar energy can be an exciting prospect, but determining how many solar panels are required for your solar system can seem like a daunting task. The key lies in understanding the factors that influence the size of your solar energy system. With this guide in hand, calculating how many solar panels you need is actually really easy.
By following these eight simple steps, you can calculate the ideal number of solar panels you need to power your home efficiently and cost-effectively.
How to determine how many solar panels do you need?
Step 1: Analyse your power bill
Step 2: Consider your power usage
Step 3: Set your solar power production goal
Step 4: Account for inconsistent power production
Step 5: Assess average daily sunlight
Step 6: Calculate your solar panel system size
Step 7: Obtain solar quotes for your ideal system size
Step 8: Calculate how many solar panels you need
Step 9: Do you have enough Square Meterage on your roof?
Step 1: Analyse your power bill
To kickstart the process, examine your monthly and yearly power bills to gain insights into your energy consumption patterns. By understanding your current usage and its associated costs, you can establish a baseline for your solar energy production goals. This enable you to calculate how many solar panels you need.
Consider this example: If your monthly electricity bill amounts to R2,000 (equivalent to R24,000 per year), it’s unlikely that you would require a solar array capable of generating R40,000 worth of energy. To determine your energy needs accurately, examine your bills for both summer and winter seasons to understand your typical usage patterns throughout the year.
Step 2: Consider your power usage
In addition to costs, it’s essential to evaluate your monthly and yearly power usage in kilowatt-hours (kWh). Take the total kWh used in the last 12 months and find the average. This figure will serve as a starting point for estimating the amount of power your solar panels need to generate.
To obtain a reliable estimate of your energy usage, calculate the sum of kilowatt-hours (kWh) consumed in the past 12 months and determine the average. For example, if your total energy usage over the year amounts to 15,000 kWh, it would average out to approximately 1,250 kWh per month. This average serves as a useful starting point in determining the power output required from your solar panels.
Keep in mind your life circumstances can change, and energy requirements can increase or even decrease. You need to plan for this. Are you
- Planning on having kids?
- Installing a pool?
- Adding a second fridge?
- Adding air-conditioning?
- Etc…
Step 3: Set your solar power production goal
Define your desired level of energy production from solar panels. Most experts recommend aiming for around 80% of your current power usage. By setting a clear goal, such as producing 80% of 1500 kWh per month, you can establish the energy output your solar system should aim to achieve.
Step 4: Account for inconsistent power production
Solar energy production varies throughout the year, depending on factors such as location and weather. Consider the excess energy your system may generate during peak sunlight periods.
- What happens if your system produces excess energy in the summer months? Where will the excess go?
- Do you have a way to store this excess energy? (solar battery)
Step 5: Assess average daily sunlight
The amount of direct sunlight your location receives affects the efficiency of your solar panels. Areas with more direct sunlight yield higher energy production.
Calculate the average daily hours of direct sunlight your region receives, as this information will contribute to determining the required system size.
South Africa is blessed with abundant sunshine throughout the year, making it an ideal region for solar energy. The average number of sunshine hours in most areas of South Africa exceeds 2,500 hours annually (6.8 hours per day).
On average, South Africa experiences a 24-hour global solar radiation average of about 220 W/m2, surpassing the figures of approximately 150 W/m2 in certain parts of the USA, and roughly 100 W/m2 in Europe and the United Kingdom. This high level of solar radiation places South Africa among the top countries globally in terms of local solar energy resources.
Step 6: Calculate your solar panel system size
Using the data obtained from previous steps, you can now calculate the size of your solar energy system. Divide your average monthly power usage by the product of the average daily sunlight and 30 days. The result will provide the required kW solar system to meet your energy needs.
kWh per month / (avg sunlight per day x 30) = kW solar system
So using our power usage example from Step 2 of 1,250 kWh per month:
1,250 kWh per month / (6.8 sunlight per day x 30) = 6.12 kW solar system
A 6.12 kW solar system signifies a solar array that generates 6.12 kWh of energy per hour of direct sunlight. For example, in a location with 6.8 hours of direct sunlight, a 6.12 kW system produces approximately 41.6 kWh per day. If your daily energy consumption is lower than this figure, you can be confident that your system will adequately meet your average energy needs.
Step 7: Obtain solar quotes for your ideal system size
With the system size in mind (6.12 kW solar system), reach out to solar panel installers to request quotes for the specific kW-sized solar array you calculated. Personally, I would round up to the nearest kW. So, in this case, round 6.12 kW up to 7 kW.
This quoting phase allows you to explore options and gather information on costs and installation requirements.
Step 8: Calculate how many solar panels you need
Considering the wattage of the solar panels you intend to purchase, multiply your system size (in kW) by 1000. Then, divide the result by the wattage of the panels. This calculation will reveal the number of panels required. Adjust the wattage and recalculate as needed based on your preferences, solar panel availability and available roof space.
A 7 kW system has a power output of 7000 W.
If you choose 450W solar panels, then the calculation becomes 7000 / 450 = 15.56 (rounded up to 16) solar panels.
Step 9: Do you have enough Square Meterage on your roof?
The average residential solar panel is approximately 1.6m-1.7m tall x 1.0m wide.
The majority of residential solar panels are sized at 1.7m tall x 1.0m wide, covering an area of 1.7 m2. Although the wattage of solar panels is going up year on year, most installs ins 2023 are currently configured at about approximately 450W per solar panel.
Assuming you are using 450W and 1.7 m2 solar panels:
| Solar Panel System Size | Number of Solar Panels Required | Approximate Roof Space Required |
| 2kW | 5 | 9 m2 |
| 3kW | 7 | 12 m2 |
| 4kW | 9 | 16 m2 |
| 5kW | 12 | 21 m2 |
| 7kW | 16 | 24 m2 |
| 8kW | 18 | 31 m2 |
| 10kW | 23 | 40 m2 |
| 12kW | 27 | 46 m2 |
| 15kW | 34 | 58 m2 |
Conclusion
By following these eight simple steps, you can confidently determine how many solar panels you require for your home. Taking into account factors such as power bills, usage patterns, sunlight availability, and efficiency, you can make an informed decision that maximizes energy production while minimizing costs. Embrace the power of solar energy and embark on a sustainable journey toward a greener future.
