This article will help you quickly understand what size solar system is right for you in terms of the following three calculation methods. However, it is important to note that these calculations are only estimates, as the amount of power generated by the solar panels will vary depending on the tilt angle of the solar installation, temperature, latitude, and season.
Before you do this, you need to estimate the peak hours of sunlight in your area for each day of the year, not the hours of sunshine. The following picture shows the peak hours of sunshine time in different parts of the world.
1. Calculate Based On Monthly Electricity Consumption
You can find out how much electricity you consume each month in your monthly electricity bill.
The formula is: Solar system power size (kw) = electricity consumed per month (kWh) / 30 / 0.8 / peak sunshine hours (h)
The formula in 30 is calculated according to 30 days a month. 0.8 is the system efficiency, temperature correction factor, etc. on the impact of solar power generation, here the value of 0.8 is only the average value, different types of solar systems have differences.
2. Calculation According To The Power Of Appliances And The Time Of Consumption
You need to know the rated power and time of use of each appliance.
The calculation formula is: Solar system power size(kw) = (Appliance A power(kw) x daily power consumption time(h) + Appliance B power (kw)x daily power consumption time(h) + Appliance C power(kw) x daily power consumption time(h) + …. ) / 0.8 / Peak sunshine hours (h)
3. Calculation Based On Roof Area
If your roof area is large enough, this does not need to be considered.
3.1 If it is a horizontal concrete roof: Solar system power size(kw) = roof area (m²) x 0.15
3.2 If it is a pitched roof: Solar system power size(kw) = roof area (m²) x0.21
Usually, we calculate the size of the solar system power needed based on the monthly electricity consumption, then we choose the right size of inverter and go on to calculate the size of the battery capacity. You can find the calculation in my other guide article.