Evaluating solar contractors: a twelve-point technical checklist

The short answer

Two quotations for the same roof can differ by thirty per cent and both be honest. The difference is usually module tier, inverter specification, mounting methodology, whether structural assessment was performed, and how much regulatory work is included. Establish those five and the price gap explains itself.

Before the quotation

1. Was a structural roof-load assessment performed? Ask for the calculated additional load per square metre and the drawings it was assessed against.

2. Was the site surveyed, or drawn from satellite imagery? Imagery does not show obstructions accurately, establish shading, or reveal roof condition.

3. Was the system sized against your consumption data? A system sized from roof area optimises for the contractor’s revenue, not your payback.

Equipment

4. Which modules, specifically? Manufacturer, model, wattage, cell technology. “Tier-1” describes bankability, not quality.

5. What warranty structure? Product and performance warranties differ in duration. Ask what output is guaranteed at year 25 — current n-type modules commonly guarantee 87% to 90%, and 30-year performance warranties are now standard, so 80–85% indicates older p-type stock — and ask who honours it if the manufacturer exits Malaysia.

6. Which inverters, and what service life? Inverters need replacement at least once. A quotation omitting this understates lifetime cost.

7. What mounting system, and is it penetrative? Ask how penetrations are sealed and whether the seal is water-tested.

Scope and aftercare

8. Who lodges TNB, Suruhanjaya Tenaga and Bomba submissions? If not the contractor, the quotations are not comparable.

9. What is excluded? Commonly: structural reinforcement, roof repair, switchboard upgrades, extended cable runs, scaffolding. Get exclusions in writing.

10. How is installation sequenced around production? Ask when grid tie-in occurs and what interruption it requires.

11. What does the O&M arrangement cover? Cleaning frequency, monitoring, fault response time, what is chargeable.

12. Who will still exist in year ten? Ask for references from installations commissioned at least three years ago — not last quarter.

Normalise before you compare

Convert every quotation to cost per watt-peak, after adding back anything excluded that you will pay for anyway. Malaysian installations sit at RM 3.00 to RM 4.20 per Wp residential and RM 2.20 to RM 3.20 commercial. A 12 kWp quotation at RM 39,000 is RM 3.25 per Wp — reasonable. The same system at RM 24,000 is RM 2.00 per Wp — well below anything transacting in this market — and warrants these twelve questions rather than a signature.

If our figures sit above a quotation you have received, these questions will usually show where the difference is — and occasionally the answer will be that the other contractor scoped something better than we did.

Verify what you are told

Most claims in this market are checkable with modest effort. Company registration can be verified, as can standing with SEDA. Module and inverter models can be looked up, including warranty terms published by the manufacturer rather than restated by the installer. SEDA registration status can be confirmed, as can professional registrations held by named engineers with the Board of Engineers Malaysia, the statutory registration body under the Registration of Engineers Act 1967.

References are the most useful and least used check. Ask for installations commissioned at least three years ago and put specific questions: has it leaked, has output matched projection, how quickly were faults attended, is the contractor still responsive. A contractor confident in their work provides older references without hesitation.

Contract terms that decide what happens when something goes wrong

Payment milestones should track delivery stages rather than weight heavily toward signature. Liability for roof damage during and after installation should be explicit. The defects liability period should be stated along with what it covers.

Warranty administration matters as much as duration — a twenty-five year module warranty is only useful if someone processes a claim in year eighteen. Ask who administers claims and what happens if the manufacturer withdraws from Malaysia. Also establish what happens if generation materially underperforms projection: some contractors commit to investigating and remedying, others treat projections as indicative. Both are defensible, but you should know which you are buying.

Signals that should give you pause

Pressure to sign on a time-limited discount. A quotation issued without a site visit. Reluctance to name specific equipment models. No structural assessment offered. Regulatory submissions described vaguely. No physical address. References only from recent months. An unusually large deposit weighted before any work.

None is individually conclusive. Several together describe a pattern that has left a considerable number of Malaysian building owners with underperforming systems and nobody to call.