When investing in solar power, one of the most important decisions a business must make is whether to invest directly under an EPC/CAPEX model or adopt a solar Power Purchase Agreement (PPA).
Both models can be implemented on the same rooftop using the same solar technology. However, they differ significantly in how a business allocates capital, owns the asset, manages operations, and assumes long-term project risks.
Therefore, simply comparing the EPC cost with the PPA electricity tariff is not sufficient to make an investment decision. Businesses should also evaluate their electricity load profile, cost of capital, expected facility operating horizon, solar self-consumption ratio, and risk tolerance.
What Are the Differences Between EPC, CAPEX, and Solar PPA?
CAPEX refers to the capital a business invests to acquire or create long-term assets.
In a solar EPC project, the business typically provides the investment capital and appoints an EPC contractor to carry out engineering design, equipment procurement, and system construction. Upon completion and contractual handover, the business owns and manages the solar asset in accordance with the agreed project structure.
In contrast, under a PPA, the investor typically provides the capital, owns the system, and is responsible for its operation. The business consumes the solar electricity generated and pays for it according to the tariff and terms specified in the agreement.
At its core, choosing between EPC/CAPEX and PPA is a choice between:
Invest to own the energy asset, or purchase solar electricity through a long-term PPA without upfront investment in the system.
This is the most fundamental distinction to understand before assessing the financial performance of each model.
Solar EPC/CAPEX: Invest to Own the Asset
Under the EPC/CAPEX model, the business bears the upfront investment cost but also owns the solar PV system and directly captures the economic value generated by the asset.
When system capacity is properly designed to match the facility’s load profile, on-site solar generation and consumption reduce the amount of electricity purchased from the grid. After the payback period, the system continues to generate economic value for the business throughout its remaining operating life.
Another key advantage is greater control.
The business has greater flexibility to select equipment, define technical standards and O&M strategies, upgrade the system, or integrate additional BESS and EMS solutions as its energy needs evolve.
However, ownership also comes with responsibility. The asset owner must manage risks related to energy yield, performance degradation, equipment failure, maintenance, and long-term system performance.
Therefore, the lowest EPC price is not necessarily the best investment option.
For a CFO, the key question should be:
How much value will today’s investment generate over the entire lifecycle of the solar PV system?
Solar PPA: Reducing CAPEX Without Eliminating Risk
Under a solar PPA, the business does not need to provide the full upfront capital required for the solar system.
The investor is responsible for the asset, while the customer purchases the electricity generated under an agreed pricing mechanism.
A PPA can therefore be suitable for businesses that prefer to preserve CAPEX for production lines, factory expansion, technology investments, or other core business activities.
However:
Zero upfront CAPEX không đồng nghĩa với zero project risk.
A PPA does not eliminate risk. It shifts part of the risk from asset ownership to contractual obligations.
Businesses should carefully assess the PPA term, electricity tariff, price adjustment mechanism, O&M responsibilities, rooftop usage rights, electricity purchase obligations, procedures for roof repairs or changes in production operations, and contract termination conditions.
Therefore, a PPA should not be selected solely because its initial electricity tariff is lower than the grid tariff.
What matters more is the total economic value and the obligations the business must fulfill over the entire PPA term.
EPC/CAPEX vs. Solar PPA
The table above reflects a typical structure. Actual terms and conditions may vary depending on the specific project.
The Most Important Factor When Choosing Between EPC and PPA: Electricity Load Profile
A common mistake in commercial and industrial solar investment is to start with the question:
“How much does the EPC system cost?”
or:
“How much lower is the PPA tariff compared with the current electricity tariff?”
In practice, the effectiveness of both EPC and PPA models depends first and foremost on how the facility consumes electricity.
Solar power is generated primarily during daylight hours. Therefore, facilities with stable daytime electricity demand typically achieve higher self-consumption rates than those with low weekend loads, seasonal production, or frequently changing operating schedules.
This leads to an important principle:
The optimal solar capacity is not necessarily the maximum capacity that can be installed on the rooftop.
A larger system may generate more kWh, but that does not necessarily translate into greater economic value if the additional electricity cannot be effectively utilized.
Before choosing between EPC and PPA, businesses should first determine:
How much electricity does the facility consume during solar generation hours? What proportion of the solar output can be consumed on-site? And is this load profile likely to remain stable over the long term?
Cost of Capital Can Influence the Choice Between EPC and PPA
The same solar PV system may lead to different investment decisions depending on the company’s financial structure.
If a business has strong cash flow, a low cost of capital, and expects to operate the facility over the long term, EPC/CAPEX may be attractive because the business owns the asset and retains the economic value generated by the system.
Conversely, if capital is being prioritized for production expansion or other activities with higher expected returns, a solar PPA may be a more suitable option.
The key point is:
The option with the lowest total cost does not necessarily create the greatest value for the business.
Businesses should therefore assess cash flow, NPV, IRR, cost of capital, and opportunity cost together before making an investment decision.
O&M Directly Affects Solar Investment Performance
System performance does not end at COD.
Once the system enters operation, energy yield and Performance Ratio should be continuously monitored to identify potential causes of performance loss at an early stage.
Under an EPC/CAPEX model, the business should clearly define who is responsible for O&M after system handover.
Under a PPA, the investor is typically responsible for system operation because its revenue is directly linked to the electricity generated and sold. However, customers should still carefully review commitments related to performance, system availability, and incident response time.
At 365Energy, O&M and performance management are treated as integral parts of the project lifecycle, rather than as supplementary services provided only after EPC completion.
Are Solar PPA and DPPA the Same?
An on-site solar PPA should not be considered the same as a DPPA.
PPA is a broad term referring to a power purchase agreement. In contrast, DPPA in Vietnam is a direct power purchase mechanism governed by a specific regulatory framework.
Therefore, the fact that a business signs a PPA with a solar investor does not automatically mean that the project participates in the DPPA mechanism.
Businesses should separately review the ownership structure, contracting parties for electricity purchase and sale, grid connection arrangement, metering configuration, and the applicable legal framework for each project.
When Should a Business Choose EPC/CAPEX?
EPC/CAPEX may be more suitable when a business has access to appropriate capital, expects to operate the facility over the long term, and wants to own the energy system.
This model also provides greater flexibility in technology selection, O&M management, BESS integration, and future system upgrades.
Conversely, a solar PPA may be more suitable when a business wants to limit CAPEX allocated to energy infrastructure, prioritize capital for core business activities, and is comfortable entering into a long-term electricity purchasing relationship with an investor.
There is no single model that is right for every business.
365Energy Perspective: Start with the Data, Not the Model
365Energy does not recommend starting a solar project by first choosing between EPC and PPA.
The first step should be to analyze the facility’s actual operating data:
load profile, projected solar generation, self-consumption ratio, rooftop conditions, production plans, expected facility operating horizon, and financial objectives.
Based on this data, EPC/CAPEX and PPA can then be evaluated within the same analytical framework.
More importantly, both options must be evaluated using the same assumptions for energy yield, degradation, O&M, and operating period. If one option is assessed using more favorable assumptions, the comparison will no longer be reliable.
The ultimate objective is not to select the model with the lowest price, but to determine:
Which investment structure creates the greatest net value at a level of risk the business is willing to accept?
Conclusion: Is EPC or Solar PPA Better?
There is no single answer.
EPC/CAPEX is generally more suitable for businesses that want to own and control the asset, have access to appropriate capital, and plan to operate the facility over the long term.
A solar PPA is generally more suitable for businesses that want to reduce CAPEX pressure and transfer part of the investment and operational responsibility to the investor.
Therefore, instead of asking:
“Which is cheaper, EPC or PPA?”
Businesses should ask:
“Given our current load profile, capital structure, operating plans, and risk tolerance, which model creates greater long-term value?”
365Energy supports businesses in analyzing electricity load profiles, determining the appropriate solar PV capacity, developing EPC and PPA options, and evaluating investment performance across the entire project lifecycle.
This content is intended for general analytical purposes only and does not constitute legal or financial advice, nor does it replace a project-specific assessment.