Methodology | Window Replacement Lab

Every number on this site is either sourced or labelled as a planning estimate. This page explains the difference, how the calculator is built, and what the model cannot see.

1. The calculator is component arithmetic, not a lookup table

A window price is four things stacked: the unit, the labour to set it, the removal of the old one, and the weatherproofing and trim around the opening. The calculator prices each of those separately and adds them. That is why the result is a range rather than a single figure — each component has its own low and high band.

The published component bands are on thecalculator page in the transparency table. If a reader disagrees with a result, they can point at the component that caused it instead of arguing with a black box.

2. Two markets, stated not averaged

The same opening costs roughly twice as much through a full-service replacement company as it does buying the unit and hiring a local installer. Both are real installed prices; they are different products. Most published cost guides pick one and present it as "the" average, which is why their ranges disagree so widely.

This site exposes the choice as a switch instead of hiding it. A single blended average would be easier to publish and less useful.

3. What is measured and what is planned

Input	Status	How it is handled
Unit price by style and material	Published band	Ranges cross-checked against several independent cost guides for the same model year
Labour per opening	Published band	Insert and full-frame are priced separately; bay and bow get their own band
Size multiplier	Published band	Small 0.8×, standard 1.0×, large 1.3×, oversized 1.7×
Regional labour multiplier	Planning band	A regional adjustment, not a measured wage. Labelled as such on the tool.
Permit allowance	Planning band	$0–$350 flat, scaled by opening count; the local jurisdiction decides
Energy savings figures	Published research	Cited to the programme or study that produced the number

The honest limit: we do not have a live wage feed wired into the tool. The regional multiplier is a planning adjustment with a stated basis, and it is treated as one everywhere it appears. A reader who needs a measured local labour rate should start from the Bureau of Labor Statistics OEWS series for the relevant trade and metro, which is public.

4. Why published window costs disagree

Three separate reasons, and they compound:

Market. Installer-plus-unit versus full-service contract, roughly 2× apart.
Unit specification. A clear double-pane vinyl unit and a Low-E triple-pane fiberglass unit are both "a window".
Scope. A number that excludes trim, disposal and permit is not comparable with one that includes them.

When we publish a range we state the market and the specification it describes. When a competitor's range differs from ours, the useful question is which of the three is behind the gap — not which number is "right".

An aluminium window frame in a modern wall — The frame is one line. The glass, labour and trim are three more.

A vinyl double-hung window in a timber frame — The default case the calculator opens on: vinyl double-hung, insert fit.

A custom window being fitted into an opening — Non-standard sizes are the largest source of quote-to-quote spread.

Impact-rated windows on a coastal house — Impact units sit in their own band because the frame changes too.

5. What we have not tested

We do not manufacture windows, install them, or run a test lab. When a claim comes from a manufacturer's published rating, a code document, a government dataset or an installer report, the page says which. We do not imply first-hand testing we did not perform, and we do not publish review scores for products we have not handled.

6. Corrections

If a price band moves outside its published range, or a reader finds an error, we update the article and its "last updated" date. Emailcontact@windowreplacementlab.comwith the page and the correction.