Quote A says €4,500. Quote B says €5,200. Quote C says €6,000. Instinctively, your eyes go to the bottom-right - the final number.
This is the #1 mistake. Comparing quotes solely by price, without decoding the technical specs, is like comparing a base-model car with a fully loaded one by looking only at the badge on the bonnet. You need an "apples to apples" comparison.
It is very common for one quote to simply say "Alumil Windows" or "Europa". This means absolutely nothing. The major extrusion companies produce dozens of series - from very basic (cold) to ultra-premium.
Ask for the exact series code (e.g. Europa 5500 or Alumil S560). Only then can you check whether all three fabricators offer the same aluminium thickness and the same thermal-break technology. If one gives you a light, older series and the other a heavy-duty one, the price difference is fully justified.
Even worse, some quotes simply say "thermally broken profile" without specifying the series. A lightweight thermal-break profile (with narrow polyamide) can deliver almost half the insulation of a premium system with wide polyamide and triple sealing.
Glass covers 80% of the window. "Double glazing" is no longer enough - you need to know exactly what glass you are getting.
Every quote must state: Is it energy-coated (Low-E)? Which manufacturer (e.g. Saint-Gobain, Guardian)? Does it have Argon gas in the cavity (if yes, insulation is much better)? What is the thickness - a 4mm-16-4mm unit is cheaper and less soundproof than a 5mm-16-4mm one? And whether balcony doors use safety glass (Triplex).
If one quote includes triple glazing (4-12-4-12-4) and the others double, the price will naturally be higher. But insulation will be 30-40% better. To compare fairly, ask for the U-value (Ug) declaration of each glass - if two quotes say "energy glass" but one gives Ug 1.0 and the other Ug 1.4, the price difference is fully explained.
This is where the biggest price gap usually hides. A "cheap" quote may give you basic 2-point locks instead of multi-point perimeter locking mechanisms.
Quote A may have basic 2-point locks. Quote B may have branded (e.g. GU, Siegenia, Giesse) perimeter multi-point mechanisms offering top-level anti-burglary protection. Ask for the brand and type.
Are they plastic (PVC) or aluminium with polyurethane insulation? Huge price difference. If motorised, are the motors branded (e.g. Somfy with 5-year warranty) or of "unknown origin" that will burn out within the first year?
Are you getting basic spring-loaded screens (which break easily) or Plissé-type screens with Kevlar cord and tracks? The price difference can reach €100-150 per opening.
The cheapest quote often omits important services, which you will be asked to pay "extra" on installation day.
Does the price include 24% VAT? Many quote ex-VAT to look cheaper. Does it include removal of old windows? Rubble collection and recycling? Use of a crane if you live on a high floor?
For quotes to be comparable, they must match on: exact same profile series (not just same brand), same glass type (thickness, energy coating, gas), same hardware category (perimeter or basic), same shutter type (material and motor brand), and inclusion of all labour (removal, rubble, crane, VAT).
Once you equalise all the above, you will find that differences between serious fabricators are minimal - in the range of 5%-10%. If a quote remains 30% cheaper, rest assured that quality has been "cut" somewhere you cannot read on paper. Spend 10 minutes comparing properly and you will save your investment for 30 years!
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