Instructions for calculating installed capacity for rooftop solar power systems
Installing rooftop solar power helps households, businesses, etc. take advantage of the roof area to generate electricity for daily life and production. This is a solution that helps investors optimize costs and save monthly electricity bills effectively.
During the peak heat wave in 2024, electricity demand skyrocketed and continuously set records. Electricity in many localities had to cut off electricity during peak hours. Households and businesses gradually saw the benefits that solar power brings. However, basic knowledge about solar power systems has not been widely disseminated to the people.
The following article will guide you to install a solar power system for the highest efficiency.
Installing rooftop solar power helps households and businesses optimize costs and save monthly electricity bills.
How to calculate solar power system capacity based on electricity bill
Suppose a family uses 600,000 VND – 1,000,000 VND of electricity per month. With the average electricity price from Vietnam Electricity (EVN) for all levels being 2,500 VND/kWh, we get a monthly consumption of 250 – 400kWh, an average of 8 – 13 kWh per day.
Vietnam has an average of 3 to 5 peak hours of sunshine in most areas. With the highest usage (13kwh/day) on the average sunshine coefficient (4 hours), we will have a system capacity of 3.3 Kwp of solar power. An average 400 Wp photovoltaic panel has an area of 2m2, so to install a 3.3kwp system, we need at least 8 panels covering an area of 16m2.
Currently, the cost of installing a 3.3 Kwp grid-connected rooftop solar power system ranges from 50 – 60 million VND, depending on the customer’s economic choice.
| System Capacity | Number of Panels | Area | Output (month) | Price List (Reference) |
| 3 Kwp | 8 | 16m2 | 360 – 450 kWh | 50 – 60 million |
| 5 Kwp | 13 | 26m2 | 600 – 750 kWh | 80 – 90 million |
| 7 Kwp | 19 | 40m2 | 840 – 1200 kWh | 100 -110 million |
| 10 Kwp | 25 | 60m2 | 1200 – 1500 kWh | 150 – 170 million |
| 15 Kwp | 37 | 90m2 | 1800 – 2250 kWh | 200 – 220 million |
| 20 Kwp | 50 | 120m2 | 2400 – 3000 kWh | 270 – 290 million |
These cost estimates are indicative only and do not take into account the complexity of your roof or the equipment you choose.
With the above calculation, a 3.3 Kwp capacity system when we invest will take 05 years to recover the initial amount spent, the rest is our profit (from 10-20 years of profit).
