Do you design rooftop solar for Thailand? Your utility checks the design before it connects the system. The utility is PEA (Provincial Electricity Authority) or MEA (Metropolitan Electricity Authority). MEA’s service area includes Bangkok, Nonthaburi and Samut Prakan. The office of the Energy Regulatory Commission (ERC) issued a notice on 4 April 2025. It puts generation under 200 kVA in one band and 200 kVA to under 1,000 kVA in another. kVA is a size unit for AC equipment.
Here is what the vendors publish. OpenSolar lists Thai among its proposal languages, and its core app is free. HelioScope lists single-line diagrams (SLDs, simple drawings of how the system is wired) on every plan. PVsyst describes a feed-in tariff, a self-consumption tariff and a limit on injected power. SAM is free and takes flat buy and sell rates. SurgePV lists roof modeling, shading, yield, financial modeling, bill of materials and proposals in one product, priced per user. None of the pages we read shows a baht price.
This is a desk comparison of what each vendor publishes, checked October 2026. We have not run side-by-side tests. SurgePV published this page and sells one of the tools on it. Local rules below come from the ERC, PEA and MEA. Tool facts come from each vendor’s own site.
This page covers design tools. For general software, see solar software in Thailand. For quotation tools, see solar proposal software in Thailand.
Criteria used: single line diagram output, tariff and sell-rate modelling, export limit modelling, Thai language and baht support, size range.
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Best-For Picks for Thailand
- Thai-language proposals in a free core app: OpenSolar. Thai is on the vendor’s list of supported translations. You still have to translate a proposal template by hand. API Access and connectors are charged from 16 April 2026.
- Single line diagram on every plan, for commercial rooftops: HelioScope. Its pricing page lists single-line diagrams on all plans. Basic designs up to 1.25 MW (DC, the direct current the panels make) and Pro up to 5 MW. The ERC notice sizes are in kVA, so compare AC and DC sizes.
- Yield study with a sell tariff or a limit on injected power: PVsyst. Its help pages describe a fixed feed-in tariff, a self-consumption tariff and a grid power limitation setting. It runs only under Windows. We found no proposal feature in its help pages.
- Free finance model with flat buy and sell rates: SAM. Its manual lists flat buy and sell rates, with or without net metering. SAM has no layout or diagram output on the pages we read.
- Roof model to bill of materials and proposal in one product, priced per user: SurgePV. Ask in a demo for the Thai drawings and tariff set-up you need. Its pricing page and published scope do not state them.
Comparison Table
Listed alphabetically. This is not a ranking; pick by the situation above. Prices checked October 2026 on each vendor’s own page. No vendor page we read shows a baht price.
| Tool | Best for | Price | Free or paid | Decisive scope fact |
|---|---|---|---|---|
| HelioScope | SLD on every plan | $159 USD per license per month, or $1,620 USD per license per year (Basic) | Paid; 14-day free trial (help center) | Basic designs up to 1.25 MW (DC); Pro 5 MW; Enterprise 30 MW |
| OpenSolar | Thai proposals, free core app | Core app free; API Access and connectors charged from 16 April 2026 | Free core app, paid API and connectors | Recommends 3D designs under 500 kW; users have modeled up to 5 MW |
| PVsyst | Sell tariff and export limit in a yield study | CHF 700 per year (PVsyst 8 Professional) | Paid; one-month free trial (product page) | Runs only under Windows |
| SAM | Free yield and finance model | Free; register by email for a software key | Free | Desktop app for Windows, Mac and Linux |
| SurgePV | Roof model to BOM and proposal, per user | $1,899 per user per year (1 user); no baht price published | Paid, guided demo | BOM and proposal in scope; no Thai drawing format stated |
Thailand Criteria Matrix
Documented means the vendor’s own pages state it. Partial means the pages state only part of it, or state it for other countries. Not stated means the pages we read in October 2026 do not mention it. There are no scores or weights.
| Tool | SLD output | Tariff and sell-rate modelling | Export limit modelling | Thai language and baht | Size range |
|---|---|---|---|---|---|
| HelioScope | Documented (all plans; DXF export) | Partial (Utility Rate Editor on Pro; no Thai tariff stated) | Partial (Energy Arbitrage help article: Export Limit input in kW) | Not stated (help center menu lists six languages, none Thai; USD price) | Documented (1.25 MW, 5 MW, 30 MW DC) |
| OpenSolar | Partial (templates for AU, NZ, US, CA, UK, FR, DE, IT, ES and IN; Thailand not listed) | Documented (custom tariff with a compensation mechanism) | Documented (Export Limit design setting; set to 0 kW in the off-grid article) | Partial (Thai listed for proposals; baht not stated) | Partial (3D under 500 kW recommended; up to 5 MW by simplifying) |
| PVsyst | Partial (editor “still work in progress”; no storage) | Documented (fixed feed-in tariff; self-consumption tariff; hourly tariff file) | Documented (grid power limitation applied at inverter level) | Not stated (12 languages, none Thai; CHF price) | Not stated |
| SAM | Not stated | Documented (“Flat buy and sell rates (with or without net metering)”) | Documented (manual: Grid Limits page, grid export limit input) | Not stated | Documented (“SAM does not restrict system sizes”) |
| SurgePV | Partial (electrical workflow support; no diagram output named) | Partial (financial modeling; no Thai tariff stated) | Not stated | Not stated (USD price only) | Not stated |
P50 and P90 are yield levels. PVsyst says the annual production has a 50% probability of exceeding the P50 value. It says it has a 90% probability of exceeding the P90 value.
Two things stand out. No vendor page we read describes a Thai tariff or the household sell programme’s rate. Of the five tools, only OpenSolar’s pages we read list Thai, and only for proposals. A tool that is Not stated on a row may still do it, so ask for it in a demo.
Tool Entries
HelioScope
Best for: commercial rooftop and carport designers who want a single line diagram on every plan. Pro covers up to 5 MW (DC).
Not the right choice if: you need Thai screens or a baht price, or you want a free tool. The pages we read do not say which languages the app supports. It is also not right if you need the Utility Rate Editor on a low plan. The pricing page lists it from Pro.
What the vendor documents: on its pricing page, all plans list rooftop, carport, ground-mount and battery layout. They also list CAD export, single-line diagrams, an 8760 production report (a yield for each hour of the year), “Global weather coverage” and shade reports. Pro adds a Utility Rate Editor, financial analysis tools, sales proposals, and P90, P95 and P99 values. Enterprise adds single-axis trackers and export to PVsyst. The help center says the single line diagram exports in DXF format (a drawing format that CAD programs open). Its condition set article lets you pick a weather source or upload your own file. You can also edit monthly soiling losses (dust and dirt on the panels). Its Energy Arbitrage article has an Export Limit input in kW for storage simulation. The article says it caps the net AC power flowing to the grid.
Price (checked October 2026): Basic $159 USD per license per month, or $1,620 USD per license per year on annual billing. Pro $259 USD per month, or $2,640 USD per year. Enterprise is custom per project. Basic and Pro licenses include 1 user. The help center lists a 14-day free trial, one per customer.
Limitations: Basic designs up to 1.25 MW (DC), Pro 5 MW and Enterprise 30 MW. The ERC bands are in kVA, which is AC. The help center menu lists English, Español, Deutsch, Français, Português and Nederlands. We found no Thai option there.
Vendor link: helioscope.aurorasolar.com
OpenSolar
Best for: small teams that want a core app the vendor calls free and want to send proposals in Thai.
Not the right choice if: you need an SLD template for Thailand. The help article lists templates for AU, NZ, US, CA, UK, FR, DE, IT, ES and IN. It is also not right if you need Thai screens without translating a proposal template yourself. And it is not right if you need 3D designs above 500 kW without simplifying them.
What the vendor documents: the proposal language article lists 13 languages: English, Dutch, Swedish, Spanish, French, Norwegian, Thai, German, Polish, Portuguese, Italian, Danish and Finnish. It says you need a proposal template that has been translated by hand. A custom tariff has a Country field and flat, time-of-use, tiered and demand rates. The solar compensation mechanism can be net billing, net billing with credit carryover, buy all sell all, or net energy metering. OpenSolar suggests you send the customer’s bill to its support team to build the tariff. The off-grid article says to set the Export Limit to 0 kW in Design, Advanced Settings. Output uses PVWatts version 6 at hourly resolution or the System Advisor Model with 3D shading, per its help article.
Price (checked October 2026): the core app is free of charge for solar professionals, per the vendor (free page). From 16 April 2026 the vendor charges for API Access and supported connectors. Source: its 16 February 2026 post. We did not compare those fees.
Limitations: its commercial design article recommends keeping 3D designs under 500 kW. It also says users have modeled systems up to 5 MW by simplifying settings. The pages we read do not mention a Thai tariff, baht or a Thai SLD template.
Vendor link: opensolar.com
PVsyst
Best for: yield studies where you need to enter a sell tariff and a self-consumption tariff, or model a limit on injected power. It also suits you if you want a choice of weather sources.
Not the right choice if: you need proposals, a bill of materials or a roof model from the same tool. We found no proposal feature in its help pages. It is also not right if you work on a Mac or in a browser. The product page says PVsyst only runs on Windows.
What the vendor documents: a grid power limitation setting for cases where “a limit to the injected power is sometimes required by the grid manager”. It applies the limit at inverter level. Its feed-in tariff and self-consumption page describes a fixed feed-in tariff, peak and off-peak tariffs and an hourly tariff file. It also describes one tariff for self-use and one for selling the overproduction. The product page lists weather import from Meteonorm 9, NASA-Power, PVGIS-TMY, NLR/NSRDB TMY, Solcast TMY, Solar Anywhere and Solargis. TMY means a typical meteorological year, one year of typical hourly weather. It has a single line diagram editor.
Price (checked October 2026): CHF 700 per year for PVsyst 8 Professional. Discounts are 5% for 2 to 4 licenses, 15% for 5 to 9 and 20% for 10 or more. The product page lists a one-month free trial. No baht price is published (CHF).
Limitations: the single line diagram editor is “still work in progress”. It covers strings, inverters and transformers and does not include storage. The software has 12 languages. Thai is not one of them. We searched its help index and found no page that names Thailand.
Vendor link: pvsyst.com
SAM
Best for: engineers who want a free finance and yield model with flat buy and sell rates. SAM stands for System Advisor Model.
Not the right choice if: you need a layout drawing, a single line diagram or a proposal. The pages we read do not mention them. It is also not right if you need Thai screens or baht support. The pages we read do not mention either.
What the vendor documents: the home page calls SAM a “free desktop application for techno-economic analysis”. The SAM manual (version 2020.2.29) says the Electricity Rates page can hold flat buy and sell rates, time-of-use energy charges, demand charges and tiered rates. It says SAM does not restrict system sizes. It also lists monthly soiling losses and P50 and P90 runs. The Grid Limits page has inputs for a grid power export limit. The weather data page names the NLR National Solar Radiation Database. NLR is the National Laboratory of the Rockies. The page says the database provides free weather data for “many countries of the world”.
Price (checked October 2026): free. The download page says you register with your email address to get a free software key. The current version is 2026.7.3 for Windows, Mac or Linux.
Limitations: the manual we read is an older version than the current release. The pages we read do not mention a Thai tariff.
Vendor link: sam.nlr.gov
SurgePV
SurgePV is our product.
Best for: teams that want roof modeling, array layout, shading analysis and energy-yield modeling in one product. They also want financial modeling, electrical workflow support, bill-of-materials output and proposal generation, priced per user. They should confirm the Thai outputs in a demo. See solar design software for the product page.
Not the right choice if: you want a self-serve trial. SurgePV offers a guided demo. It is also not right if you need a baht price in writing first. It is also not right if you need Thai-language screens (not stated on the pages we read). OpenSolar lists Thai among its proposal languages. SurgePV’s pricing page lists US dollars per user per year. Outputs support design and documentation but do not replace approval by the responsible engineer, authority, lender or utility. SurgePV’s published product scope does not list monitoring or ERP (business management software) tools. It does not list a CRM (customer database), and /pricing lists lead management.
What the vendor documents: 3D roof modeling, array layout, shading analysis, energy-yield modeling, financial modeling, electrical workflow support, bill-of-materials output and proposal generation.
Price (checked October 2026): Individual: $1,899 per user per year (1 user). 3 seats: $1,499 per user per year. 5 seats: $1,299 per user per year. Prices are in US dollars. Confirm any baht amount and taxes in a written quote.
Limitations: results depend on source data, assumptions and equipment models. The pricing page and published scope do not state a PEA or MEA drawing format or a Thai tariff. They also do not state an export limit or a design size limit.
Vendor link: surgepv.com.
Thailand Rules That Shape the Choice
Who does what. ERC is the Energy Regulatory Commission. PEA and MEA are the two distribution utilities named in the ERC notice. MEA’s news page says its service area includes Bangkok, Nonthaburi and Samut Prakan.
License bands. The ERC office notice of 4 April 2025 sets the steps for notifying generation that is exempt from an electricity license. It covers two bands. Under 200 kVA per generation source, you need no controlled-energy production license. From 200 kVA to under 1,000 kVA, you also need that license (Por Kor 2) after the equipment is installed. The notice cancels the ERC office notice of 28 September 2022. We did not read the rules for 1,000 kVA and above.
How you apply under 200 kVA. First you finish the design. Then you send a request to check your design and electrical system through the utility’s online system. ERC counts that request as your exemption notice. The utility checks it, and if it allows the connection, it shares your details with ERC. ERC emails you the result within 5 days of getting the utility’s data.
What the utilities publish. PEA says requests to connect a generator that does not sell power go through its ppim.pea.co.th system, for all consumer types. MEA’s producer page lists separate no-sale routes for homes up to 10 kW and for larger homes, businesses and factories. It also lists approved inverters and Zero Export Controller devices. A Zero Export Controller is a device that protects against power flowing back to the grid.
Drawings. PEA’s network service code (B.E. 2559, which is 2016) has a connection request form for generators. The form lists a single line diagram and a protection diagram as extra documents. An engineer must endorse the drawings. We did not find a separate PEA checklist for small rooftop systems on the pages we read.
Selling surplus: the 2026 household programme. This programme is called Solar Phak Prachachon in Thai. The ERC press release of 11 June 2026 described a draft notice for homes. The ERC then issued the final notice, dated 26 June 2026, which it lists on its programme page. It sets a target of up to 500 MW. Each meter may offer up to 5 kW for sale at 2.20 baht per unit. The contract runs for 10 years from the SCOD or the COD date, whichever comes first. SCOD is the scheduled date when power starts to flow to the grid for sale, and COD is the actual date. Supply must start within 2027. The utilities take applications from 1 July 2026, first come first served, until 500 MW is reached. PEA’s Q&A page says the programme is for PEA’s Category 1 (home) customers who own the meter. It says you may install more than 5 kW for your own use, but only up to 5 kW AC is offered for sale. It also says you can add a battery. Read the final notice for the full terms before you model income.
Language and currency. The ERC, PEA and MEA pages are in Thai, and ERC rates are in baht per unit. A Thai customer reads proposals in Thai and baht. So check Thai language and baht support before you buy.
Regulator pointer. The Energy Regulatory Commission (erc.or.th) regulates generation, and PEA (pea.co.th) and MEA (mea.or.th) handle connection.
How We Ordered These Tools
SurgePV publishes this page and is a vendor on this list. Its entry uses the same vendor-page sources and template as every other tool here.
We did not rank these tools. They are listed alphabetically, and the best-for picks come from the matrix above.
- SLD output: utilities check a design before they connect it, and PEA’s code lists an engineer-endorsed diagram. We did not assess whether any tool’s diagram passes PEA or MEA review.
- Tariff and sell-rate modelling: the household programme pays a flat 2.20 baht per unit, for up to 5 kW per meter. We did not assess whether any calculation is correct.
- Export limit modelling: MEA lists approved Zero Export Controller devices. We did not assess whether any tool matches those devices.
- Thai language and baht: Thai customers read proposals in Thai and baht. We did not assess translation quality or tax lines.
- Size range: the ERC bands stop at 1,000 kVA in the notice we read. We did not assess speed on large designs.
Not Compared Here
Aurora Solar, PVcase and PV*SOL premium are compared on the global solar design software list but not on this page. Reslink publishes an article on Thai rooftop solar, but its pricing page is written for Indian EPCs, so it is not compared. Nearby design lists are for Vietnam and Malaysia.
Sources and Dates
Vendor pages were read in October 2026. HelioScope (pricing and three help center articles linked above). OpenSolar (pricing post, 16 February 2026, free page and the help articles linked above). PVsyst (shop, product page and help pages linked above). SAM (home, weather data and download pages, and the 2020.2.29 manual at sam.nlr.gov). SurgePV (pricing). Local rules come from the ERC notices and press release, PEA’s connection news and Q&A pages and network service code, and MEA’s producer page. The ERC notices are scanned files, and we read them as page images. The ERC bands come from the 4 April 2025 notice itself, not from news reports. The household programme terms come from the 26 June 2026 notice.
See SurgePV on a Thai project
Book a guided demo and ask for the Thai outputs you need.
Book a Free DemoRelated Solar Software Lists
- Solar software in Thailand, the all-purpose list for the country
- Solar proposal software in Thailand, for quotation tools
- Design software for Vietnam and Malaysia, the nearest country design lists
- Best solar design software, all markets
Frequently Asked Questions
What is the best solar design software in Thailand?
It depends on the job. OpenSolar lists Thai among its proposal languages, and its core app is free. HelioScope lists single-line diagrams (SLDs, simple drawings of how the system is wired) on every plan. PVsyst describes a feed-in tariff, a self-consumption tariff and a limit on injected power. SAM is free and takes flat buy and sell rates. SurgePV lists roof modeling, shading, yield, financial modeling, bill of materials and proposals in one product, priced per user. None of the pages we read shows a baht price.
Do I need a license to install rooftop solar for my own use in Thailand?
The ERC office notice of 4 April 2025 sets two bands. Generation under 200 kVA per source needs no controlled-energy license. Generation from 200 kVA to under 1,000 kVA also needs a controlled-energy production license. You still apply to your utility, PEA or MEA, to connect. Other approvals are outside what we read. Check the notice and your utility before you design.
Do PEA and MEA require a specific design tool?
None of the pages we read names a required tool. The ERC notice describes sending a request to check your design and electrical system through the utility’s online system. PEA’s network service code lists a single line diagram and a protection diagram, endorsed by an engineer, as extra documents on its generator connection form. Any tool is fine if its drawings let your engineer check and endorse them.
Can solar design software make the single line diagram for a Thai connection request?
Some tools can. HelioScope lists single-line diagrams on every plan. PVsyst has a single line diagram editor that it calls work in progress. OpenSolar’s help article lists SLD templates for AU, NZ, US, CA, UK, FR, DE, IT, ES and IN, not Thailand. SurgePV lists electrical workflow support but does not name a diagram output.
Which tool can model a limit on exported power?
PVsyst describes a grid power limitation setting that it applies at inverter level. OpenSolar has an Export Limit design setting, and its off-grid article sets it to 0 kW. HelioScope’s Energy Arbitrage help article has an Export Limit input in kW, and SAM’s manual has a Grid Limits page with a grid export limit input. The other pages we read do not describe an export limit. MEA also publishes a list of approved Zero Export Controller devices. Ask for a demo with your own load profile.
How much does solar design software cost in Thailand?
None of the pages we read shows a baht price. HelioScope Basic is $159 USD per license per month, or $1,620 USD per license per year. PVsyst 8 Professional is CHF 700 per year. SAM is free. OpenSolar’s core app is free, but the vendor charges for API Access and supported connectors from 16 April 2026. SurgePV Individual is $1,899 per user per year. Ask each vendor for a written quote in baht.
