Roof Lantern vs Skylight Cost Difference Calculator

How this calculator works

This calculator compares typical UK supplied-and-fitted price ranges for the two options, drawn from published 2026 industry cost guides. Your inputs scale those base ranges: the calculator multiplies the per-unit range for each option by the number of units and by adjustment factors for the choices you make below, then shows both totals side by side along with the estimated difference between them. Because real quotes vary, everything is expressed as a range from a realistic low to a realistic high rather than a single figure.

A roof lantern typically costs around to fitted in 2026 against to for a flat skylight, making the lantern roughly three to six times the cost of covering equivalent roof area with skylights. Two or three well placed skylights usually deliver more even light distribution than a single lantern for considerably less money.

Number of units

Enter how many units you are comparing. Note that one lantern is often compared against two or three skylights covering similar roof area, so you may want to run the calculation both ways.

Specification level

Two windows that look similar from the street can sit at very different price points. Budget products use simpler profiles, standard hardware and basic glass. Mid-range covers the typical A-rated units most UK installers quote by default. Premium covers high-end systems with upgraded security hardware, better thermal performance, special finishes or designer profiles, and typically adds around 30 percent to the price.

Where you live

Labour rates are not uniform across the UK. Published cost guides consistently show installation prices in London and the South East running roughly 20 to 30 percent above the national average, driven by higher labour costs, travel, parking and congestion charges. The calculator applies an uplift of around 20 percent if you select London and the South East. Product prices themselves are broadly similar nationwide, so the difference mostly reflects fitting costs.

What else affects the price

The lantern premium buys architecture, not just light: a raised glazed centrepiece that adds height, drama and kerb appeal to an extension, which flat skylights cannot replicate. Skylights win on cost, simpler installation, easier cleaning and better thermal performance per pound, and they suit minimalist designs where the roofline stays clean. Structural requirements differ too, since a lantern needs an accurately built kerb and a roof designed for its weight and opening, while skylight openings are smaller and simpler to trim. On south-facing roofs, budget for solar control glass with either option.

Planning permission, building regulations and certification

Most roof glazing falls under permitted development rights, provided the units do not project more than 150 millimetres above the roof plane and sit no higher than the highest part of the roof, but conservation areas, listed buildings and flats have tighter rules, so check with your local planning authority before ordering. Building regulations apply regardless of planning status, covering structural alterations, thermal performance, safety glazing and, in loft conversions, escape and ventilation requirements. Installers registered with a competent person scheme can self-certify that replacement glazing complies with the regulations and issue a certificate you will need when selling the property; for structural roof work, building control involvement is normally required.