1. Read actual electricity units from your bill.
Use historical kWh 6–12 months and separate Demand, Ft, VAT or TOU range values from energy quantities.
Article · Calculate system size
With a 50,000-baht monthly electricity bill, what solar PV capacity is appropriate?
A rough calculation formula that beginners can use to estimate the initial system size by themselves. With real calculation examples Before having the team analyze the actual electricity bill again
Quick answer
Electricity bill 50,000 baht per month. How many kWp of solar should be installed?
It is still not possible to determine the appropriate size from the amount of 50,000 baht alone. Because business bills may include Demand, Ft, VAT and TOU rates, actual power units (kWh) must be used along with Load Profile or power used during sunny days. So the kWp size can be properly estimated.
The example below teaches you how to make an estimate from energy data. It is not a system size recommendation for every business.
Calculation formula
A 3-step preliminary assessment
Let's start with kWh data and actual load patterns. The baht amount should not be converted into units at a single rate.
2. Find the load during power production.
Use Load Profile, Smart Meter or schedule. to see that the approximate range 08:00–17:00 n. How much electricity can be used from solar?
3. Estimate site-specific energy yield
For a rough estimate, an estimate of 90–120 kWh per kWp per month may be used, and the software simulation from the coordinates, direction, angle, and shade can be confirmed again.
Hypothetical example
Example when real energy data is available
- From the bill: The business uses electricity 12,500 kWh per month.
- From Load Profile: There is daytime energy that can be supported by solar approximately 6,000 kWh per month.
- From the estimated output: 90–120 kWh per kWp per month
- Energy framework: 6,000 ÷ 90–120 ≈ 50–67 kWp before checking other constraints.
The installation size cannot be immediately concluded from this number. The power graph must be checked periodically. Roof area Transformer power, connection points, budget, and conditions not to send back electricity are also included.
Why might the numbers be different?
Factors that make the actual numbers different from the samples
- Actual electricity rates may differ from the assumed average. Especially businesses that have TOU or Demand Charge rates.
- The proportion of daytime electricity usage in each location is not the same.
- The roof area may not be enough for the calculated size.
- The budget and investment goals of each business are different.
For this reason, the numbers from these rough calculations should only be used as a starting point for discussion. The actual appropriate system size must come from an analysis of the electricity bill and a site survey by the team.
Frequently asked questions
A question that beginners often ask about calculating system size.
Why do each location calculate the system size differently? Even though the electricity bill is the same?
Because the proportion of electricity used during the daytime The actual electricity rate (normal or TOU/Demand Charge) and the electricity usage behavior of each location are different. Even though the amount on the bill is the same
If the roof area is not enough for the calculated size, what should you do?
Can be installed as much as the space can support first. Then it can help reduce some electricity bills. Or consult an expert to see other options, such as arranging the panels for maximum efficiency based on the available space.
Business and residence Are system sizes calculated differently?
The calculation principle is similar. But the proportion of electricity used during the daytime is often very different. Businesses or factories that are open during the day often use a higher percentage of daylight than ordinary homes.
Why do I have to send the electricity bill to the team first?
An actual electricity bill shows the tariff, energy consumption, and usage pattern more accurately than a rough formula. The team uses this information to design a system for the actual site.
How much does a system this size cost?
Price depends on system size. Selected equipment and complexity of the work site Therefore there is no fixed number. You should request a quotation with clearly separated items after surveying the actual work site. See all working steps at solar PV installation service
Want to know the system size that really suits your electric bill?
Send the electricity bill to the PTH GREEN team to help evaluate. There is no charge.
Related articles: What is a Solar Rooftop? · 5 Things you need to know before installing a solar rooftop · What is the difference between On-Grid and Hybrid?