A developer with a 40 MW project and a term sheet often hears the same advice: “Use a tier 1 solar engineering firm, or the bank will push back.” Sometimes that advice is right. Often it costs months and a large fee premium for work that a specialist could deliver to the same standard.
Quick answer. There is no official “tier 1” list for solar engineering firms. The term comes from BloombergNEF’s Tier 1 list of module makers, which tracks bankability, not quality. For engineering, the question is which role your financing needs. A lender usually picks its own independent engineer from an approved panel. Design and owner’s engineering can go to a mid-market specialist whose work survives that review.
TL;DR
- "Tier 1" is a BloombergNEF module-maker label. No body grades engineering firms the same way.
- Separate three roles: designer of record, owner's engineer, and the lender's independent engineer.
- The lender's independent engineer is the role most likely to need a large, lender-approved name.
- Design work can go to a mid-market specialist if its deliverables pass independent review.
- Ask your lender for its approved list before you hire anyone.
This guide is for developers, independent power producers (IPPs), and EPC owners scoping engineering for a financed project. If your question is local versus national vendors for rooftop drafting in India, read local vs national design vendors in India instead.
What does “tier 1” mean in solar?
In solar, “tier 1” almost always means the BloombergNEF (BNEF) PV Module Maker Tier 1 list. It is a bankability screen for module brands. It is not a ranking of engineering firms.
BNEF’s 2019 methodology counts a maker as Tier 1 if its own-brand, own-made modules went into six projects financed non-recourse by six different banks in the past two years, per a copy of the BNEF methodology (2019). The July 2025 version requires each of those projects to be at least 10 MW, as quoted by BISOL’s position statement (2025).
BNEF also warns buyers and banks not to use the list as a measure of quality. It tells them to hire a technical due diligence firm instead.
Why this matters. When someone says "tier 1 engineering firm," they mean a large, well-known firm a lender already trusts. That is a reasonable test for one role. It is a weak test for the rest of the engineering scope.
Which engineering roles does a financed solar project have?
A utility-scale or large C&I project usually has three distinct engineering roles. Each has a different client and a different test for “good enough.”
| Role | Works for | Main output | Who usually chooses the firm |
|---|---|---|---|
| Designer of record | EPC or developer | Layouts, single-line diagrams, structural calcs, IFC drawings | EPC or developer |
| Owner’s engineer (OE) | Developer or owner | Design review, EPC contract support, construction monitoring | Owner |
| Independent engineer (IE) | Lender or tax equity investor | Technical due diligence report, construction draw sign-off | Lender, often from an approved panel |
The independent engineer is the lender’s technical adviser. It is typically appointed by the lender and paid by the project sponsor. Its report reviews the design, energy yield, contracts, and budget before money is released.
Our checklist on lender’s due-diligence engineering in India lists what that review looks for, document by document.
When is a large engineering firm the right call?
Size earns its premium in a few specific situations. In these cases, a large name lowers financing risk or meets a contract term you cannot change.
- The lender requires an IE from its panel. If the bank names three approved firms, you hire one of them. No mid-market firm can stand in for that role.
- The project is first-of-a-kind for the lender. New markets, new technology, or a first deal with a development finance institution (DFI) can lead credit committees to prefer a familiar reviewer.
- The contract needs a large balance sheet. Some EPC or offtake contracts set professional liability insurance limits that only big firms carry. Check the clause before you shortlist.
- You need one firm across many disciplines at once. Transmission, substation, geotechnical, environmental, and grid studies under one contract can justify a full-service firm.
BNEF’s own list of technical due diligence firms includes DNV, Black & Veatch, Kiwa PVEL, and Clean Energy Associates. That list is about module and project due diligence. It is a fair starting point for IE shortlists, not a ranking. For the scopes where a big name adds cost without adding comfort, see when not to hire AECOM or Black & Veatch.
When does a mid-market specialist make more sense?
Most of the engineering hours on a solar project sit in the designer-of-record scope. That work is repeatable, software-driven, and checked by the IE anyway. Here a specialist often wins on speed and focus.
Mid-market specialist: strengths
- Senior engineers often work on your project directly
- Solar-only focus, so fewer generalist handoffs
- Faster revision cycles on layouts and SLDs
- Lower fees for repeat design packages
Mid-market specialist: limits
- Rarely on a lender's IE panel
- Smaller insurance limits
- May not cover transmission or environmental studies
- Bench depth varies, so check who does the work
A specialist is a good fit when the lender has already appointed its IE and needs a clean design to review. It also fits when the project is a repeat of a design type the lender has financed before.
The decision table: which firm for which scope?
Use this table before you issue an RFP. Match each scope line to a trigger, not to a brand.
| Scope | Large firm needed when | Specialist works when |
|---|---|---|
| Lender’s independent engineer | Lender names an approved panel | Lender allows any qualified reviewer and accepts the CV |
| Owner’s engineer | Owner has no in-house technical team and a complex EPC contract | Owner needs design review and site monitoring on a standard plant |
| Energy yield (P50/P90) | Lender requires a named third-party yield report | Yield study is for bid stage or internal sizing |
| Detailed design (IFC) | Contract demands one firm for all disciplines | Solar layout, electrical, and structural can be scoped separately |
| Grid and substation studies | Utility requires a firm with a track record on its network | Studies are small and the utility gives a clear template |
| Permit plan sets | Rarely | Almost always, with a licensed engineer where the AHJ requires a stamp |
The P50 and P90 line deserves care. If the lender wants its own yield check, a specialist’s PVsyst report becomes the input the IE tests, not the final word. Our guide on how lenders validate a PVsyst report shows what that test covers.
How does a split-scope model work?
Many financed projects end up splitting the work. The lender’s IE is a large, approved firm. The design work goes to a specialist who builds to the IE’s checklist from day one.
- Get the IE’s requirements early. Ask which yield method, uncertainty budget, and design standards it expects.
- Brief the designer on that list. The specialist builds the layout, SLD, and yield report to match.
- Hold a pre-review. The owner’s engineer, or the designer’s senior reviewer, checks the package against the IE list.
- Submit once. A package built to the reviewer’s list should need fewer comment rounds.
This model keeps the bank’s comfort where it matters. It also avoids paying large-firm rates for routine drafting.
See the deliverables first. Before you decide, compare real files: PVsyst reports with P50/P90, ground-mount layouts, and STAAD Pro structural reports. Download design samples and check them against your lender's list.
What should you ask any engineering firm, large or small?
Brand alone does not answer these questions. Ask them of every bidder.
- Who on the team will do the work, and who reviews it?
- Which lenders or IEs have reviewed your deliverables before?
- What professional liability insurance do you carry, and at what limit?
- Which code editions and yield methods will you use for this site?
- How many revision rounds are included, and what triggers a change order?
If you are building to DFI terms, read what AfDB, IFC, and USAID evaluate. The IFC project developer’s guide to utility-scale solar (2015) is also worth reading on financing roles.
How Heaven Designs helps
Heaven Designs is a mid-market solar engineering firm. It is not a lender’s IE, and it does not replace one. It does the design scope that the IE reviews.
- Solar ground mount design for utility-scale layouts, civil, and structural packages
- Engineering reports, including PVsyst yield reports with P50/P90
- MW-scale project management consultancy for owner-side review and site support
The team is company-stated at 50+ engineers across Surat and Ahmedabad, with work in 15+ countries. On an 11 MW DC tin-shed rooftop project in a Gulf country, Heaven Designs took over from an unresponsive freelance team and helped the client avoid a ₹5 crore penalty on that project.
If you have a financed project and your IE’s checklist, send us the scope for a quote. We reply within 1 business day.
FAQ
Is there an official list of tier 1 solar engineering firms?
No. The best-known “tier 1” list in solar is BloombergNEF’s list of module makers. No similar list exists for engineering firms. Lenders keep their own approved panels for independent engineers.
Does a bank require a large engineering firm for my solar project?
Usually only for the independent engineer role, and only if its credit policy says so. Ask the lender for its approved panel. Design work is normally the sponsor’s choice.
What is the difference between an owner’s engineer and an independent engineer?
The owner’s engineer works for the developer and protects the owner’s interests. The independent engineer works for the lender and reports on risk to the bank. They should not be the same firm.
Can a mid-market firm produce a bankable PVsyst report?
It can produce a report that a lender’s IE reviews and accepts. Whether it is accepted depends on the method, data, and uncertainty assumptions, not the firm’s size.
Is a tier 1 module the same as a quality module?
No. BNEF says its list is not a measure of quality. Use independent module testing and factory audits for that.