How to compare building quotes like-for-like (worked example)

Steve Parker

Sep 19

5 min read

To compare building quotes like-for-like, list the full scope once from the drawings, map every quote onto that list, mark each item a quote leaves out as NOT PRICED, give each gap an allowance, then compare the adjusted totals. In our sample, the lowest headline quote finished $1,785 above the lowest like-for-like.

The quotes and tables in this post are samples we made for illustration, not a real project. The suppliers, the house and every price are made up so the method is easy to follow.

Why the lowest quote is often not the cheapest

A quote total tells you what a supplier priced. It does not tell you what they left out. Put 3 quotes side by side and the lowest headline is often the one with the shortest scope, not the sharpest rates.

Whoever accepts the quote wears the gaps. A line nobody priced comes back later as an extra, a variation or a cost you absorb.

The sample: 3 electrical quotes, 1 house

Our sample is the electrical package for a 4-bed new build of 212 m². Three suppliers have quoted, all in NZD excl GST.

Sample: three headline totals for one electrical package. A looks lowest by $13,860.

Supplier A: $29,500
Supplier B: $43,360
Supplier C: $44,050

On headline figures alone, A is the lowest by $13,860. It is tempting to stop there and ring A.

How to compare quotes like-for-like in 5 steps

1. Write one scope list before you open the quotes

Build the list from the drawings and the spec, not from any one quote. Build it from the cheapest quote and you inherit its gaps. Our sample list has 13 lines, from a 24-way RCBO switchboard through 46 double power points and 48 LED downlights to testing, CoC and ESC.

Put the quantity on every line. If one quote prices 48 downlights and another prices fewer, you want to see that on line 5, not after the job starts.

2. Map every quote onto that list

Put each quote's price against the matching scope line, one line at a time. Keep all figures on the same GST basis; our 3 sample quotes are all excl GST.

3. Mark every gap NOT PRICED

A blank is not a zero. If a quote is silent on an item, or lists it under exclusions, mark that line NOT PRICED.

Sample: the same 3 quotes on one scope list. Supplier A leaves 6 of 13 lines unpriced.

In the sample, A leaves 6 of the 13 lines unpriced:

Mains cable and trench
Temporary builder's supply
Exterior lights (8)
Heat pump supplies (3)
Data and TV points (10)
EV charger supply circuit

C leaves 1 line unpriced: the temporary builder's supply. B prices all 13.

4. Put an allowance on every gap

Now give each NOT PRICED line a dollar figure. In the sample we used the average of the quotes that did price it:

Mains cable and trench: B $4,180 and C $4,520 average to $4,350
Exterior lights (8): $2,950
Heat pump supplies (3): $1,900
Data and TV points (10): $3,285
EV charger supply circuit: $1,780
Temporary builder's supply: only B priced it, at $1,380, so A and C each carry $1,380

A's 6 allowances add up to $15,645. C's single allowance is $1,380.

An average is a placeholder, not a price. Ask the supplier to price the missing lines in writing. Their answer tells you whether the gap was an oversight or an exclusion.

5. Compare the adjusted totals

Sample: each gap filled with the average of the quotes that priced it. A adds $15,645.

With every gap filled:

Supplier A: $29,500 + $15,645 = $45,145
Supplier B: $43,360 + $0 = $43,360
Supplier C: $44,050 + $1,380 = $45,430

B is now the lowest like-for-like. A has gone from $13,860 under B to $1,785 over it.

Sample: like-for-like, B is lowest at $43,360 and A, the lowest headline, is $1,785 over it.

Check the rates, not just the totals

Now look at the lines every quote priced. In the sample, all 3 suppliers priced 7 of the 13 lines, and A is dearer than B on all 7. Three examples:

Double power points (46): A $8,920, B $8,510
LED downlights (48): A $7,780, B $7,390
Switchboard, 24-way RCBO: A $4,580, B $4,420

So A's $29,500 was never a sharper price. It was a shorter scope: higher rates on 7 lines, nothing on the other 6.

A published case: 3 supplier quotes, 1 bill of materials

This sample is invented. For a real one, read our electrical supplier quote comparison. An Auckland electrical subbie held 3 supplier quote documents for a commercial fit-out. The sharper headline was missing lines, and on the scope both wholesalers priced, the incumbent came out about $15–18k cheaper.

That case took a slightly different route: compare only the lines every supplier priced, and put everything else into a scope-gap register. The 2 methods end in the same place. Neither lets a missing line count as a saving.

Builders, subbies and homeowners: same method

Builders and head contractors. Every subbie quote you carry into a tender or contract sum needs this check. If you are sitting on 4 subbie quotes and a tender closing Thursday, see our builder quote review.

Subcontractors. Your supplier pick becomes part of your cost floor. Our cost floor vs target price case builds a real electrical tender up from a cost floor of about $180–190k. If you price all 13 lines and keep losing to quotes that price 7, why am I losing tenders covers 7 diagnosable reasons.

Homeowners. Ask each builder to price the same plans and the same spec, then run the same 5 steps. For residential building work of $30,000 or more incl GST, the builder must also give you a checklist and prescribed disclosure information before you sign (Building Act 2004 s362D).

When all 3 quotes share the same wrong quantity

Like-for-like only works if your scope list is right. If all 3 suppliers price 48 downlights and the drawings show more, every quote is short together and the comparison will not catch it. Our Takeoff Verification checks the quantities against the drawings for $490 + GST per trade, back in 48h.

FAQ

Is the lowest quote usually the cheapest? Not reliably. In our sample, the lowest headline was $13,860 under the next quote and finished $1,785 over it once its 6 gaps were priced. A low total often means a short scope.

What allowance should I use for an item a quote left out? Start with the average of the quotes that did price it. In the sample, that put $4,350 against mains cable and trench. Then ask the supplier to price the line in writing and swap your allowance for their figure.

What if only 1 quote prices an item? Use that price as the allowance for the others. In the sample, only B priced the temporary builder's supply, so A and C each carried $1,380.

Should I just pick the lowest like-for-like total? Not on the total alone. Confirm in writing that the quote covers every line on your scope list, read the exclusions and compare the line rates. In the sample, B was lowest like-for-like and also cheaper than A on all 7 lines they both priced.

Get your quotes lined up

Send us your quotes and the drawings. We put every quote on one scope list, mark each gap NOT PRICED and put a figure against it, line by line, in writing. Start with a free quote check.