Reading an Electrical Tender BoM — What NZ Head Contractors Check Before Pricing
- sp8002
- May 30
- 8 min read
10 things a senior NZ sparky checks on an electrical tender BoM before submitting a price — code-cited against AS/NZS 3000, NZECP 51, NZS 4541/4512.
By Steve Parker · Trueworks · NZ construction estimation · 8 min
Reading an Electrical Tender BoM — What NZ Head Contractors Check Before Pricing
Updated May 2026. A stamped electrical tender drawing set lands. The natural reaction is to forward the lighting schedule to your wholesaler, get a price back, add labour and a margin, submit. Across the electrical tenders Trueworks reviewed in Q2 2026, that workflow lost the head contractor an average of NZ$18,000–34,000 per build to scope gaps that were on the drawings but not in the price. The fix is a 30-minute audit, structured as 10 questions, run before pricing.
Quick answer
Before pricing an electrical tender, a senior NZ sparky should resolve 10 things on the BoM: (1) free-issue vs supply-by-EC for every luminaire Type code, (2) AS/NZS 3008.1.1 cable sizing against the DB schedule, (3) RCBO count vs MCB count from the schedule, (4) emergency lighting + exit signs to NZS 4541 + NZS 4512, (5) sub-main cable sizing under AS/NZS 3000 §3.4 and the network operator (Vector / Powerco / Aurora) connection rules, (6) cable tray dimensions against actual load, (7) the mechanical and fire interface scope split, (8) DALI vs phase-dim vs 0-10V on every dimmable circuit, (9) commissioning and testing per AS/NZS 3017, (10) Vector / network operator approval workflow and PS1 chain. Miss one and you'll pay for it in variations.
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The 10 things
1. Free-issue vs supply-by-EC for every luminaire Type code
In commercial fit-out tenders, the lighting designer typically issues some luminaire Type codes as free-issue — supplied to the head contractor, installed by the EC. Other codes are supply-by-EC — head contractor sources and installs.
Across the electrical tenders Trueworks reviewed last quarter, the average BoM had 27 Type codes. The average number of codes whose free-issue / supply-by-EC status was unambiguous from the tender documentation: 9. The remaining 18 needed an RFI before pricing.
Pricing free-issue luminaires twice (once because the designer specifies them, once because the wholesaler lists them) is the single most common scope-double-count on NZ electrical tenders. Fix it before the BoM goes out.
2. AS/NZS 3008.1.1 cable sizing against the DB schedule
The DB schedule lists circuit ratings — but the cable sizes drawn on the layout may not match what AS/NZS 3008.1.1 actually requires for the install method.
Quick check: for every circuit larger than 20A, run the AS/NZS 3008.1.1 Table 4 (multi-core in conduit, 30°C ambient) lookup vs the drawn cable size. Discrepancies almost always favour the head contractor (drawn cable undersized) but the cost to fix on site is 3–5× the cost to fix at pricing.
3. RCBO count vs MCB count from the schedule
AS/NZS 3000 §2.6.3.1 requires RCD protection on most general-purpose circuits (RCBOs preferred). The tender schedule typically lists circuit-by-circuit RCBO / MCB assignment. Two failure modes:
Schedule says RCBO, layout shows MCB only. Pricing the MCB. Site needs the RCBO. Variation.
Schedule and layout both say MCB. AS/NZS 3000 §2.6.3.1 requires RCBO. Building Consent Authority may reject. Variation.
Cross-check the schedule against AS/NZS 3000 §2.6.3 before pricing.
4. Emergency lighting + exit signs to NZS 4541 + NZS 4512
Emergency lighting layouts are usually scoped by the fire engineer, not the lighting designer. The split:
NZS 4541:2020 governs the automatic fire sprinkler system. Sparky scope = the fire panel power supply and the smoke detector to BMS interface, not the sprinklers themselves.
NZS 4512:2010 governs fire detection and alarm. Sparky scope = power to the fire alarm panel, interconnect to smoke detectors, beacon and sounder loops.
AS/NZS 2293.1/.2/.3 governs the EM lighting fittings themselves.
Two scope gaps to check: (a) the smoke detector to BMS interface — usually supply-by-EC but install by fire contractor; (b) the EM lighting test certification — usually by-EC but commonly missed in tender pricing.
5. Sub-main cable sizing + network operator coordination
Auckland: Vector. Wellington: Wellington Electricity. Christchurch: Orion. Each has its own connection-approval workflow and fault-rating requirements.
The tender drawing typically shows the sub-main from network pillar / kiosk to MSB. Check three things:
Cable size — Vector typically requires 4C × 50mm² Cu XLPE/PVC minimum on 160A 3-phase incoming; size up for distance per AS/NZS 3000 §3.4.
Fire-rated penetration — sub-main through a shear wall or fire-rated separation needs a sealed system (Promat / Hilti CFS) to maintain the rating. Not always priced.
Connection-approval programme — Vector connection approval takes 4–6 weeks from application. If the tender programme has the sub-main being terminated in week 2, the application needs to be in now, not after award. Flag it.
6. Cable tray dimensions against actual load
The drawn cable tray size on a riser layout is often the minimum that fits the shown cables. If you bid that size and a single sub-main is added during construction (very common), you'll be cutting in a parallel run. Standard allowance: up-size the riser tray by one width step above what's drawn. Cost <NZ$300 at tender, cost on site >NZ$3,000.
7. Mechanical + fire interface scope split
The single highest-variation-risk question on a multi-services fit-out: who pays for the conduit and cabling between the mechanical plant and the mechanical DB?
Default tender assumption: power to the mechanical DB is by EC (electrical); power from the mechanical DB to each plant item is by the mechanical contractor; BMS cabling is by the BMS commissioner.
In practice, the split is often: power from the mechanical DB to each plant item is also by EC, because the mechanical contractor isn't licensed for >50V install work in NZ. Variation. Confirm before pricing.
8. DALI vs phase-dim vs 0–10V on every dimmable circuit
Three failure modes on lighting controls:
| Drawing says | BoM should price | Common error | |---|---|---| | "DALI" | DALI bus + DALI driver + DALI gateway + commissioning | Phase-dim driver priced. Variation. | | "Phase-dim" | Phase-dim driver. Standard switch leg. | DALI bus priced. Over-priced — losses tender. | | Nothing — just "switched" | Standard MCB circuit. Switch on wall. | Either of the above priced. Over-priced. |
Lighting designer typically marks controls protocol on the lighting layout, not the schematic. Cross-check both before pricing the driver type.
9. Commissioning + testing per AS/NZS 3017
AS/NZS 3017 governs installation testing of LV electrical work — insulation resistance, polarity, earth continuity, RCBO trip test. Hours and equipment are a real BoM line, not "allow as part of labour."
Auckland trade rate Q2 2026: ~6–10 hours for a typical commercial fit-out, ~NZ$540–900 of senior chargehand time, plus tester hire ~NZ$120–180/day.
10. Network connection + PS1 chain
Producer Statement chain on an electrical tender:
PS1 — Design statement, by the electrical consulting engineer. Tender is priced against PS1.
PS3 — Construction monitoring, by the same consulting engineer typically.
PS4 — Construction review on completion. Issued after test certificate and Vector / network commissioning sign-off.
If the consulting engineer's PS1 doesn't specifically reference the tender drawing revision being priced, flag it. A common scope gap is the PS1 being against Rev A drawings and the tender being against Rev C drawings. The consulting engineer is the one to confirm.
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The audit, written down
A defensible electrical tender audit is 10 questions, one short paragraph each, with a yes/no answer per Type code or per circuit. ~30 minutes for a typical fit-out tender, less for a small one.
Across the 22 electrical tenders Trueworks reviewed in Q2 2026, the audit surfaced an average of 3.4 scope ambiguities per job worth NZ$5,000–12,000 each at variation rates. The cost of the audit was 30 minutes of senior time. The ROI is straightforward.
FAQ
Who pays for the free-issue luminaires?
The client / tenant pays the lighting designer's invoice for free-issue luminaires. The head contractor's tender should exclude these — typically a footnote on the BoM cover. If the head contractor prices them and the client also pays the designer separately, the head contractor is double-billed against the project budget (usually surfaces at QS check).
How do I cost an "allow as required" line in an electrical tender?
You don't. "Allow as required" is unenforceable on either side. Replace it with a specific PS (provisional sum) item and dollar allowance. Track it in the Provisional Items Register so the client agrees a number before site works start.
What's the average ±% accuracy on an electrical tender BoM in NZ?
Across the electrical tenders Trueworks priced in 2026, the post-construction reconciliation showed a ±8% spread between the tender BoM and the final installed quantity, with the variance dominated by Type-code free-issue/supply-by-EC ambiguity. Tighter pre-pricing audit halves that.
When should I push back on the lighting designer's schedule?
If the schedule has more than 5 Type codes whose supply responsibility is ambiguous, the designer should reissue the schedule with that resolved. Don't price ambiguity — price a clean schedule. Designer fee covers this clarification.
Does AS/NZS 3000:2018 require RCBOs on every circuit?
Not every circuit — but every general-purpose socket-outlet circuit under most residential and commercial occupancies under §2.6.3, plus most luminaire circuits in wet areas. Read the schedule, then cross-check §2.6 — don't price MCBs where the standard requires RCBOs.
What this article doesn't tell you
The 10 checks are NZ-specific. AU tenders run a different schedule structure (e.g. circuit-protection rules under AS/NZS 3000 differ in detail) and different network operator approval workflows.
The variation figures are sample averages from Trueworks reviews Q2 2026. Smaller fit-outs (e.g. <NZ$80,000 electrical scope) show tighter variance; bigger jobs show wider.
PS1 / PS3 / PS4 are the typical 4-step electrical engineering documentation chain. Some BCAs require additional documents (e.g. PS2 alternative solution); confirm with the consenting authority.
Vector connection windows are not guaranteed. Vector approval can stretch to 8–10 weeks during peak Auckland-CBD demand. Build a buffer.
The audit doesn't replace your own consenting engineer's review. Decision-support, not decision-maker — the BCA, the consenting engineer, and the licensed installer own the final calls.
Free-issue exclusions wording is legally load-bearing. "Excludes designer-supplied luminaires" is not the same as "Excludes Type codes X, Y, Z (per Lighting Schedule Rev C)." The second wording survives a dispute; the first doesn't.
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About Trueworks
Trueworks is built by Steve Parker — 20 years on the analytical side of NZ construction. Variation reviews, contract advisory, programme review, and AI-augmented document workflows. Trueworks is the productisation of that practice for builders: same defensible analysis, at a price and pace a NZ builder can actually use.
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