Free tool
Solar calculator: system size, annual yield and payback in Vietnam
Runs entirely in your browser: enter your monthly bill and location to see the suggested kWp, expected annual generation, yearly savings, simple payback and the roof area required.
Inputs
Estimated results
Suggested capacity
1,209.5kWp
First-year generation
1,390,909kWh/year
Annual bill savings
2,601,000,000 ₫
Simple payback
4.4years
25-year cumulative value
49,778,911,041 ₫
CO2 avoided per year
834.5tCO2/year
Roof area required
7,257m2
Remaining monthly bill
83,250,000 ₫
Includes 0.5%/year average degradation; excludes tariff escalation.
Method
- Annual generation = capacity (kWp) x regional specific yield (kWh/kWp/year).
- Suggested capacity = annual consumption x self-consumption ratio / specific yield, capped by the roof area you enter.
- Savings = self-consumed kWh x blended tariff; exported energy is not counted as savings.
- Simple payback = total capex / first-year savings, excluding O&M, financing cost and tariff escalation.
- Avoided CO2 uses a Vietnam grid emission factor of 0.6 kg CO2/kWh.
FAQ
How much does a 100 kWp rooftop system cost in Vietnam?
At an indicative 9-11 million VND/kWp for grid-tied rooftop systems, a 100 kWp plant typically lands around 0.9-1.1 billion VND depending on roof structure, cable runs and equipment configuration. Firm pricing requires a site survey.
What payback should I expect?
Sites with high daytime load and high self-consumption typically see 4-7 years of simple payback. Low self-consumption, low tariffs or heavy shading extend it.
What if we do not want to invest capex?
An ESCO or zero-capex model lets a third party fund the system while you buy electricity at a discount for the contract term. In that case the key metric is the discount on your tariff, not payback.
Does this replace a quotation?
No. It is a quick estimate. A firm proposal needs a roof survey, load profile measurement, grid connection checks and shading analysis.
Read next
Need exact numbers for your plant?
Send 12 months of invoices and a roof layout; Orca Energy will return a technical and financial proposal.
Results are indicative, based on regional reference yields and market installed costs. Orca Energy does not guarantee generation or payback for a specific project without a survey and measurement.
Want to know how much power your factory roof could generate?
Send us your last three electricity bills and Orca Energy will calculate generation, savings and the right investment option — free of charge.