By Mick O'Brien · carpenter & builder · sheds-to-homes, cabins and things that stay up in a storm
“I learned the hard way that the cheapest timber cost me $4,200 when it warped in our first gale.”
$12,000. That's what a bloke in Western Australia lost on a battery bank that died in a gale—all because he skipped the supplier check. For off-grid kit—solar, batteries, water tanks—treating a comparison framework as optional is how you end up replacing gear early or, worse, breaching regulations you didn't know existed. I've seen it too many times.
By Mick O'Brien · carpenter & builder · sheds-to-homes, cabins and things that stay up in a storm
“I learned the hard way that the cheapest timber cost me $4,200 when it warped in our first gale.”
When you're locking in a generator, battery bank, inverter, solar array, or a full kit of switchgear for an off-grid build, the supplier matters as much as the gear. A well-built framework turns "ten quotes that all look different" into a side-by-side comparison you can defend to your partner, your insurer, and your future self. Below is the framework I use on the property at Beecher — the steps, the specs table that anchors the decision, the safety boundaries, and the questions that catch the rest.
Big-ticket off-grid kit isn't commodity hardware. Two 10 kW inverters with the same headline price can differ wildly on surge handling, warranty support, firmware updates, and whether the supplier actually stocks spares. A framework forces those differences onto the page before money moves.
The construction industry solved a similar problem decades ago with written specifications: precise descriptions of products, materials, standards, equipment, services, and workmanship that sit alongside drawings to define what the contractor is obligated to deliver. Specifications are either prescriptive, performance, or a blend of the two — and they are companion documents to drawings, not a replacement. The same logic applies when you're buying gear: write down the spec, write down the requirement, and compare them side by side. (Source: RAIC, Appendix E: Specifications.)
I run every serious supplier through the same five filters, in this order:
1. Legitimacy — ABN, electrical licence (state-issued), insurances, physical address.
2. Spec match — does the product actually meet the written requirement?
3. Total cost of ownership — purchase + freight + install + consumables + maintenance + likely replacement horizon.
4. Warranty and support — terms in writing, response time, local service agent, firmware policy.
5. Documentation — datasheets, certificates of conformance, test reports, manuals.
Run them out of order and you'll talk yourself into a bargain that doesn't meet the spec, or worse, that isn't legal to connect.
Before any technical comparison, confirm the basics. In Australia that means:
This is also where you screen out the parallel-import grey market. If a supplier can't show a legitimate Australian channel, you have no local warranty path.
Write your requirement as a single page before you call anyone. For an inverter, for example, that page might include continuous output, peak/surge rating, THD under load, supported battery chemistries, IP rating, operating temperature range, communication protocols, and required protections (RCD type, anti-islanding, DC isolation).
Then make the supplier confirm each line item against the datasheet, in writing. Construction spec writers treat this as standard practice: the spec is a precise written description of products and standards, organised by division (Division 01 covers general requirements, technical divisions from 02 onward cover trade- or material-specific requirements). Off-grid gear has its own "divisions" — generation, storage, conditioning, distribution, monitoring — and the same disciplined approach applies. (Source: RAIC, Appendix E; Government of Newfoundland and Labrador, Master Specification Guide.)
Headline price is the least interesting number. Build a TCO sheet with these line items:
A cheaper unit that needs replacement at year 7 is often more expensive than a premium unit lasting 15. The same principle shows up in ESG reporting frameworks: stakeholders look past headline numbers to lifecycle and audit-ready data. ESRS, for instance, are mandatory technical standards under the EU CSRD regime, and external assurance becomes mandatory for most frameworks in 2026 — the published number has to survive scrutiny. The same scrutiny should apply to your cost sheet. (Source: Impactmaker, ESG Frameworks 2026.)
Get warranty terms in writing. Specifically:
Don't accept verbal commitments. If it's not on the page, it doesn't exist.
The cheapest suppliers cut corners here. Ask for:
If a supplier can't produce these on request, that's a filter-1 problem dressed up as a filter-5 problem.
This is the bare-bones template I adapt per purchase. Copy it into a spreadsheet and fill the requirement column before requesting quotes.
| # | Line item | Requirement (write first) | Supplier A | Supplier B | Supplier C | Pass/fail |
|---|---|---|---|---|---|---|
| 1 | Supplier ABN | Active, matches trading name | ||||
| 2 | Electrical contractor licence | Current, state-issued | ||||
| 3 | Public liability insurance | Certificate of currency on file | ||||
| 4 | Product model | |||||
| 5 | Continuous rating | |||||
| 6 | Peak / surge rating | |||||
| 7 | Efficiency at typical load | |||||
| 8 | Operating temperature range | |||||
| 9 | IP / environmental rating | |||||
| 10 | Standards compliance (list) | |||||
| 11 | Warranty (years + terms) | |||||
| 12 | Local service agent | |||||
| 13 | Lead time (weeks) | |||||
| 14 | Freight to site (AUD) | |||||
| 15 | Total cost of ownership (AUD) | |||||
| 16 | Documentation pack complete | |||||
| 17 | Payment terms |
The "Pass/fail" column is the killer: if a line is mandatory and the supplier can't tick it, the comparison stops there.
A few patterns repeat when buyers get this wrong:
The one colourful aside: chasing the cheapest quote is a bit like buying a battery based on the brochure picture. Sometimes it works out. Mostly the brochure doesn't show the cell.
Off-grid hardware isn't intrinsically unsafe, but 230V/50Hz systems, lithium battery banks, and PV arrays carrying DC string voltages all have well-documented failure modes. The framework above is designed to keep you out of trouble, not to replace a professional.
When to call a licensed professional:
Unlicensed electrical work can void your home and contents insurance, breach state electrical safety legislation, and create a lethal hazard for anyone who works on the system later. Don't do it.
1. How many quotes should I get for a big-ticket item?
Three is the working minimum — enough to triangulate price and to expose spec gaps. More than five usually adds noise without insight.
2. Is the cheapest compliant quote always the right pick?
No. TCO, warranty support, and documentation quality routinely push a mid-priced supplier ahead of a cheaper one. The framework exists to make that trade-off visible.
3. What if a supplier refuses to provide a full datasheet?
Treat it as a failed filter-5 (documentation) and a failed filter-1 (legitimacy) signal. Walk away.
4. How do I handle suppliers who won't put warranty terms in writing?
You don't. Their verbal "we look after people" is worthless on the day something fails. Find a supplier who will.
5. Do I need a separate electrical contractor licence for solar versus batteries?
The licence is for the electrician, not the technology, but the competence requirements are different. Confirm your electrician has current, documented experience with the specific chemistry and brand.
6. Are parallel-imported products ever worth it?
For non-safety-critical, easily replaced items, sometimes. For inverters, charge controllers, BMS-equipped batteries, and anything on the AC side, almost never — the absence of a local warranty path usually costs more than the savings.
A supplier comparison framework isn't bureaucracy — it's the cheapest insurance you can buy on a six-figure decision. Write the requirement first, compare against the datasheet second, and let TCO, warranty, and documentation settle the tie. If a supplier can't clear the first filter, the rest is theatre.
Worth a watch: Understanding Basics of the Power Market · CME Group
I run the same five checks on every quote that lands on my desk, no matter how good the price looks. The cheapest sticker nearly always costs me later, so I look at warranty terms, what's actually included in the line items, and whether the bloke selling it will still pick up the phone after the invoice is paid. If they can't answer those questions straight, I walk away.
If they won't break the quote down into line items, or they push me to pay the whole lot up front, that's my cue to ring a licensed tradie for a second opinion. I also treat any fine print I can't understand in plain English as a red flag. A supplier who gets funny about warranty terms isn't worth the paperwork.
I ring around all of mine every three months to check pricing and service. Markets move, and the supplier who was cheapest last year might not be this year. It also keeps them honest when they know you're paying attention rather than just setting and forgetting.
I've been burnt before on finance terms and buried clauses, so I read every line of the contract before I sign, and I ring my accountant if the spend is serious. Council approvals and BAL ratings come into it too, and I lodge all my paperwork before a single thing gets built. The bloke in WA who lost twelve grand on a battery bank is exactly why I don't skip this step.