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How the Solar Business Works, and How PPA Differs from ESCO

An industry-wide view for factory owners comparing offers from several providers
August 17, 2026 by
How the Solar Business Works, and How PPA Differs from ESCO
Pop, Thanatat

Many of our clients ask us a version of the same question. A company has approached them offering to install solar on the factory roof at no cost, then sell them the electricity at less than the utility rate. Is that as good as it sounds, and how does it differ from the other company promising to guarantee the savings?

The answer is not simple, because doing solar business covers work that varies enormously, and the information available generally comes from sellers, who explain only the model they themselves operate.

So we have written this to show the whole industry, not only the part we work in, so that you can compare the offers you receive on your own.

Who makes up the solar business

The first thing that keeps a conversation with a bidder on point is knowing where in this chain they sit.

StageWhat it does
1. Equipment manufacturersProduce the photovoltaic panels, the inverters that convert direct current into alternating current, and the mounting structures
2. Project developersFind the sites or the customers, obtain the permits, and arrange the financing
3. Design and installation contractorsDesign the system, procure the equipment, and build it
4. Asset owners and investorsHold title to the equipment and take the return on the investment
5. Operators and maintainersKeep the system generating as designed for its whole service life
6. Electricity buyersThe utility, or the factory or building that consumes the power itself
7. Data and measurement providersMake sure every party sees one set of figures that can be audited afterwards

One company may cover several stages or only one. The company offering free installation in exchange for selling you power is operating stages 2 and 4. The company guaranteeing savings usually covers stages 2 through 5. That difference is what produces the different contract types described in the next section.

There are six solar business models in Thailand

ModelWho investsWho owns the equipmentWhat to ask for in numbers
1. Self-investmentYouYouThe payback period calculated from your own electricity bills, not from a market average
2. Private power purchase agreementAn outside investorThe investor, until transfer under the contractThe tariff you will pay, against the utility rate you pay now, and the length of the commitment
3. Energy service companyDepends on the contract typeDepends on the contract typeThe guaranteed savings, the measurement method, and the baseline used for comparison
4. Solar farms selling into the gridPrivate power producersThe power producerThe tariff and the purchase volume in whichever round is currently open
5. Households selling surplus powerThe homeownerThe homeownerThe purchase tariff, the eligible system size, and the enrolment round currently open
6. Direct power purchase agreementPrivate power producersThe power producerWhether you qualify at all, which at this stage is limited to very large consumers

Three developments in the market at this stage.

First, the scheme buying surplus power from households opens and closes in rounds, the purchase volume is capped, and once it fills, enrolment stops until a new round is announced. If you are considering an installation in order to sell surplus power, check first whether the current round is still open, because finishing an installation and only then discovering the round has closed does happen.

Second, tax benefits exist for solar installations, for individuals and for companies, and the conditions are revised periodically. But these benefits have expiry dates, they have caps, and they have conditions on whether they can be combined with other benefits. Please verify them with your own tax adviser, because the amount saved through tax measures is often large enough to change the decision.

Third, direct power purchase agreements remain at pilot stage, and the first phase is aimed principally at large data centres holding investment promotion, while the rules for requesting access to the state transmission network have not been issued in final form. In practice, an ordinary factory cannot yet use this route. If someone offers it to you, ask to see the regulation that supports it.

The principle we have followed in this article is that we quote no tariff, no volume, and no benefit amount as a figure, because this class of information changes with each announced round, and an out-of-date number is more dangerous than no number. The figures you use to decide should come from announcements by the Energy Regulatory Commission, the Metropolitan Electricity Authority, the Provincial Electricity Authority, the Revenue Department, and the Board of Investment, checked on the day you decide.

What a PPA is

PPA stands for power purchase agreement. In the context of what a seller brings to you, it means an arrangement where an investor pays the entire installation cost and owns the equipment, while you commit to buying the electricity the system produces at an agreed rate for an agreed period.

The clear advantage is that you spend nothing on the investment and your electricity cost falls from the first month. But you are committing for a long time, so read all seven of these points in the contract.

  • The contract term, which is the longest commitment in the entire offer. Compare it against your own business plan and whether you will still occupy this site throughout that period
  • The tariff and the discount against the utility rate, meaning which rate it is measured against and how it is calculated
  • The annual tariff escalation, meaning what it rises with and whether it is capped
  • The minimum volume you are committed to buy. This one matters a great deal, because if the factory stops or reduces production, you may still have to pay for the minimum
  • What happens when the system stops producing, covering equipment failure, grid outages, and instructions from the offtaker to curtail output
  • The transfer of equipment ownership at the end of the term, meaning whether it transfers to you, in what condition, and at what cost
  • The conditions and costs of early termination, for instance if you relocate the factory or sell the business

Two things called PPA that are not the same thing.

Private power purchase agreementDirect power purchase agreement
Where the power comes fromA system installed on your own siteA private producer's plant somewhere else
How it is deliveredUsed directly within your own buildingAcross the state transmission network
Is it available yetGenerally available todayAt pilot stage, limited to very large consumers

What an ESCO is, and how it differs from a PPA

ESCO stands for energy service company. Its role is to carry out energy reduction measures for you, from the site survey and the analysis through the design and installation to measuring the savings actually achieved, working through a contractual instrument called an energy performance contract.

There are two contract forms.

Under a guaranteed savings contract, the provider guarantees a minimum savings figure and must compensate you for any shortfall. The provider carries the technical risk, while you arrange the financing, whether by borrowing from a financial institution or using your own funds.

Under a shared savings contract, the provider arranges the financing and covers the implementation cost itself, then takes an agreed share of the savings actually achieved over the life of the contract. The advantage for you is that you carry no risk on repaying the investment.

Two things that are commonly misunderstood.

First, solar is only one measure within energy management, not the whole of it. Other common measures include upgrading cooling systems, replacing motors with high-efficiency models, and improving compressed air systems. If a provider offers only solar, that may be because they sell solar, not because solar is the most worthwhile measure for your factory.

Second, the heart of this work is not the installation but the measurement and verification, because savings that cannot be proven cannot be billed. So the pre-improvement energy baseline has to be agreed, and so does a measurement method both sides accept, before the work starts rather than after the installation is finished. This is the single most common cause of dispute in this kind of work.

PPAESCO
What is soldUnits of electricityEnergy savings
Basis of billingThe units the system producesThe difference between baseline and actual consumption
What must be provenHow many units were producedHow much was saved against the baseline
Scope of workPrincipally solarSeveral measures combined
Difficulty of measurementModerate, measured at the meterHigher, because the effect of the measure must be separated from other factors such as changes in production volume

In Thailand the Department of Alternative Energy Development and Efficiency is the agency supporting this business, and it maintains guidance together with a system for certifying providers. Asking to see a bidder's certification status is therefore a fair question and one you should ask, alongside asking to see a sample savings verification report they have issued to another client, with confidential details redacted.

Providers in Thailand fall into four groups

Each group comes from a different background, so each is strong in different things and typically weak in different things.

GroupBackgroundUsually strong inCheck further on
Private power producers moving into solarThe power plant businessFinancial standing and the ability to invest long termContract flexibility on smaller projects
Installation contractors moving into power purchase agreementsConstruction and installation workInstallation quality and understanding of site conditionsFinancial stability across the contract term, which is many times longer than an installation job
Energy service companiesEnergy engineeringSeeing the whole factory rather than solar aloneThe method used to measure and verify savings
Technology and data providersSystems and software workCollecting data, presenting it, and making it auditableThey neither install nor invest on your behalf

We name no company in this article, because comparing companies by name while being one of the providers ourselves would not be fair to the reader. What we can do fairly is tell you what to check in each group.

What all the models have in common

Read all six models looking for what they share and you find exactly one thing: every model ties money to a measured unit of electricity.

  • Self-investment. You need to know whether the system is paying back as calculated. If output falls below plan and nobody notices, you find out years later
  • Private power purchase agreement. The investor bills you on the units produced. Every unit not measured is revenue lost to them, and every unit over-measured is cost you should not be paying
  • Energy service company. Savings must be proven against a baseline before anything can be billed
  • Solar farms. The units sold into the grid are the project's entire revenue
  • Households. Units consumed on site must be separated correctly from units sold into the grid
  • Direct power purchase agreement. There are three parties, the producer, the consumer, and the network owner, who must reconcile the units between them

The observation we would leave with you is this. The three models where the investor is an outside party, models 2, 3, and 6, involve two contracting parties who must believe the same set of figures, unlike self-investment where you are reading the data to run your own operation.

Once two contracting parties are using the same figures as the basis for billing, the measurement system stops being a support function and becomes financial infrastructure for the project. The question you should put to every bidder is this: which device does the data come from, who maintains that data, and can you reach it yourself or must you wait for their report?

Where DigitechX sits in this chain

We are at stage 7, the data and measurement provider.

We do not install solar, we do not invest on your behalf, and we do not guarantee savings. We say so plainly so as not to waste your time. What we do build is the system that collects data from the inverters and the site equipment, sends it to a processing platform, and presents it as auditable information, with alerts when the system behaves abnormally.

The details of that system are on the IoT Solar Rooftop Solution page

The reason we wrote this to cover the whole industry, when we work in only one stage of it, is that our work is only worth anything once you have chosen the business model that is right for your factory. Choose the wrong model and the best measurement system in the world will not help.

If you are weighing an offer from any provider and would like a view on the data and measurement provisions in that contract, you are welcome to send it to us to discuss, even if you end up not using our services, because better questions put to bidders make every offer you receive better.

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