Upgrading to LED Lights Measure Cut Out Sizes Choose the Right Colour and Avoid Unsafe Products

Swapping old downlights for LEDs looks simple until the new fitting drops through the ceiling hole, sits crooked, flickers on the dimmer, or turns out to be a questionable product with poor safety markings. The light itself may be small, but the details matter.

A good LED upgrade has three parts:

• The fitting must match the ceiling cut out

• The colour temperature must suit the room

• The product must meet recognised safety requirements

  
  

Miss one of those and the result can be annoying at best, unsafe at worst.

Recent trade discussion in Australia and New Zealand has put a spotlight on unsafe and non-compliant lighting products entering the market. The message is simple: do not assume a cheap LED from a random online seller is safe just because it turns on.

Here is how to get the basics right before buying.

Measure before you buy, because downlights are not one-size-fits-all.

Measure the cut out size before choosing a new light

The cut out size is the diameter of the hole in the ceiling, not the outside width of the light fitting.

This is one of the most common mistakes when upgrading to LED downlights. People remove an old light, measure the visible face or trim, then order a replacement based on that number. When the new light arrives, it does not fit the actual ceiling opening.

Know the three measurements that matter

When looking at LED downlight specifications, pay attention to these measurements.

Measurement	What it means	Why it matters
Cut out size	The size of the hole in the ceiling	The fitting must suit this opening
Overall diameter	The visible face of the light	It needs to cover the hole neatly
Recess depth	The space needed above the ceiling	It must fit safely in the ceiling cavity

For example, a downlight may have a 90 mm cut out and a 110 mm overall diameter. That means it fits into a 90 mm hole, while the trim covers the edge of the plasterboard.

If the cut out is too small, the fitting will not go in. If it is too large, the spring clips may not grip properly and the light may sit loose or fall out.

How to measure an existing cut out

Turn the light off and let it cool before touching anything. If the light is hard-wired, damaged, or you are not sure how it has been installed, call a licensed electrician.

For plug-in style downlights, the basic measuring process is:

1. Switch off the power to the light at the wall, and at the switchboard if you will be handling the fitting.

2. Gently pull the existing downlight down from the ceiling.

3. Hold the spring clips carefully, as they can snap back.

4. Measure the diameter of the actual ceiling hole.

5. Measure across the widest point, from plasterboard edge to plasterboard edge.

6. Check the measurement in millimetres.

7. Measure more than one light if you are replacing several, as older homes can have mixed cut out sizes.

   
   

Use a firm tape measure or ruler. Do not measure the shadow line, the old trim, or the dust mark around the light. Measure the hole itself.

Common cut out sizes vary by product and age of installation. In many homes, sizes around 70 mm, 90 mm and 92 mm are common, but do not guess. A few millimetres can make the difference between a good fit and a messy ceiling repair.

What to do if the hole is too large

If the existing cut out is larger than the new light requires, do not rely on the springs to “sort of” grip. That is a poor fit.

Possible solutions include:

• Choosing a downlight with the correct larger cut out size

• Using an approved adaptor plate or conversion plate

• Repairing and re-cutting the ceiling opening

• Choosing a light with a wider trim, if it is designed for that use

  
  

Adaptor plates can be useful when replacing older, larger fittings, but they should still suit the downlight and ceiling material. The finished installation should sit flat, secure, and tidy.

Check the depth above the ceiling

Cut out size is only part of the job. LED downlights also need enough space above the ceiling.

Some fittings include built-in drivers. Others have a separate driver attached by a lead. Some are low-profile and suit tight ceiling cavities. Others need more clearance.

Before buying, check:

• The fitting height

• Driver size

• Clearance requirements

• Insulation rating

• Whether it can be covered by insulation

• Whether it is suitable for the ceiling type

  
  

In New Zealand homes, insulation is often close to ceiling lights. That makes the fitting’s insulation rating especially important. Look for clear markings such as IC or IC-F, and follow the product instructions. If in doubt, ask an electrician before installing.

The hole size, not the face size, decides whether the new LED will fit.

Choose the LED colour that suits the room

LED colour is usually described as colour temperature, measured in Kelvin. It does not mean red, blue, or green decorative lighting. It describes whether white light looks warm, neutral, or cool.

The right colour changes how a room feels. It can make a lounge feel calm, a kitchen look crisp, or a bathroom feel clean and bright.

Common LED colour options

Colour temperature	Common name	Best suited to
2700K	Extra warm white	Bedrooms, lounges, feature lighting
3000K	Warm white	Living areas, dining rooms, hallways
4000K	Natural white	Kitchens, bathrooms, laundries, garages
5000K to 6500K	Cool white or daylight	Task areas, workshops, some commercial spaces

Warm white has a softer yellow tone. It feels comfortable in spaces where people relax.

Natural white is cleaner and more neutral. It works well where visibility matters, such as kitchens and bathrooms.

Cool white can feel bright and clinical in a home. It may suit garages, hobby rooms, storage areas, or places where strong task lighting is needed. Used heavily in living spaces, it can feel harsh.

Match the colour to how the room is used

A lounge does not need the same lighting as a laundry. Before choosing, think about what happens in the room.

For living rooms and bedrooms, 2700K or 3000K usually feels more comfortable. These colours pair well with timber, soft furnishings, and evening use.

For kitchens, bathrooms and laundries, 4000K is a popular option because it gives a clearer, whiter light without feeling too blue.

For garages and workspaces, 5000K may be useful if detail and visibility matter more than atmosphere.

If the house is open plan, try to keep the colour temperature consistent across connected spaces. A kitchen in 4000K beside a lounge in 2700K can work if the zones are distinct. If the fittings are close together, the mismatch may stand out.

Consider tri-colour downlights

Many modern LED downlights are tri-colour or colour selectable. These have a small switch on the fitting or driver that lets you choose between common colour temperatures, often 3000K, 4000K and 5000K.

This can be helpful when you are unsure which colour will suit the space. It also gives flexibility if the room changes use later.

Check where the switch is located. If it sits on the back of the fitting, the colour should be selected before the light is clipped into the ceiling.

Do not ignore brightness and beam angle

Colour temperature is not the same as brightness. Brightness is measured in lumens. Beam angle describes how wide the light spreads.

A downlight with a narrow beam can create bright spots and dark patches. A wider beam can give smoother general lighting. Ceiling height, room size, wall colour and the number of fittings all affect the result.

For a typical home upgrade, aim for even coverage rather than simply buying the brightest fitting on the shelf.

Different LED colours can change the feel of connected rooms.

Be careful when buying lights

The cheapest LED is not always a bargain. If a product is poorly made, falsely labelled, or not suitable for local electrical rules, the risk shifts to the person installing it and the people living with it.

Lighting products sold in New Zealand and Australia should meet relevant electrical safety and compliance requirements. Many products in this market are designed around AS/NZS standards. Depending on the product and how it is sold, markings and documentation may include details such as supplier information, ratings, model numbers, installation instructions, and compliance marks.

A trustworthy product should make it easy to answer basic questions:

• Who supplied or imported it?

• What standard does it claim to meet?

• Is it suitable for New Zealand conditions?

• What voltage is it rated for?

• Can it be used with insulation?

• Is it dimmable?

• What warranty support is available?

• Are installation instructions clear and specific?

  
  

If these answers are missing, vague, or hidden behind poor listings, treat that as a warning sign.

Why non-compliant lighting is a real concern

Unsafe lighting products can fail in several ways. The risk is not limited to the LED chip burning out.

Poorly designed or non-compliant lights may have:

• Inadequate insulation between live parts and touchable parts

• Low-quality drivers that overheat

• Weak strain relief on cables

• Incorrect or misleading safety markings

• Poor heat management

• Flammable materials in the wrong places

• Instructions that do not match safe installation practice

  
  

A product can look neat from the outside and still be badly made inside.

If a light fitting has no clear compliance information, no recognisable supplier, and no proper installation instructions, do not treat it as a harmless bargain.

This is why recent warnings from electrical industry people matter. They remind buyers that lighting is not just decoration. It is electrical equipment fitted into ceilings, often near timber, insulation and dust.

Take care with marketplace bargains

Online marketplaces can be useful, but they also make it easy for unknown sellers to offer products that may not be supported locally. A listing might use polished photos, broad claims, and confusing safety logos. That does not prove the fitting is compliant.

Be especially cautious when:

• The price is far lower than similar products from known electrical suppliers

• The listing has no clear brand or importer

• The product claims to suit every country

• The plug, driver, or wiring does not look suitable for NZ use

• The instructions are missing or poorly translated

• The seller cannot provide compliance information

• Reviews focus only on delivery speed, not electrical quality

  
  

For fixed electrical products, buy from reputable lighting suppliers, electrical wholesalers, established retailers, or electricians who stand behind what they install.

Check dimmer compatibility before you buy

LED dimming is another area where cheap upgrades can disappoint.

Old dimmers were often designed for halogen or incandescent loads. Some work poorly with LEDs. Symptoms include flickering, buzzing, lights not turning fully off, or a very limited dimming range.

Before buying dimmable LEDs, check:

• The downlight is marked as dimmable

• The dimmer is LED compatible

• The number of fittings suits the dimmer load range

• The brand provides a compatible dimmer list, if available

  
  

If dimming matters, it is worth matching the fittings and dimmer properly from the start. Guessing can lead to repeat callouts and frustration.

Clear labels and instructions are part of a safer lighting product.

Bring the upgrade together before installation

A good LED lighting upgrade starts before anyone cuts, clips, or wires anything. The buying decision should be based on the ceiling, the room, and the product quality.

Use this quick checklist before committing.

Measure the existing ceiling holes

Record the cut out size in millimetres. Check more than one fitting if replacing several lights.

Check the visible trim size

Make sure the new downlight will cover the existing hole neatly.

Confirm ceiling cavity space

Allow for the fitting body, driver, cable and any required clearance.

Choose the right colour temperature

Use warmer light for relaxing spaces and cleaner white light for task areas.

Check the insulation rating

Make sure the fitting suits the way it will sit near or under ceiling insulation.

Buy from a reputable source

Choose products with clear compliance information, proper instructions, and local support.

Use a licensed electrician where required

Fixed wiring is not a DIY guessing job. If the installation is hard-wired or anything looks uncertain, get qualified help.

Avoid mixing too many different fittings

If you are upgrading a whole home, try not to buy a few lights from one place, a few from another, and a few random replacements later. Even when fittings look similar, they can differ in colour, brightness, beam angle, trim colour and dimming behaviour.

That can create a patchy result.

For the cleanest finish, choose one suitable model for each type of space, then keep a record of:

• Brand

• Model number

• Colour temperature setting

• Cut out size

• Warranty details

• Supplier

  
  

This makes future replacements much easier.

Think beyond the light fitting

The best downlight will still perform poorly if the layout is wrong. Replacing one-for-one is common, but it is not always ideal.

Older halogen layouts sometimes used too many fittings, too close together. Other rooms may have dark corners because the original lights were poorly placed. If you are renovating, repainting, or re-lining ceilings, it may be worth reviewing the layout rather than simply copying the old one.

Good lighting often uses layers:

• Ceiling downlights for general lighting

• Pendants for dining or kitchen islands

• Wall lights for softer evening light

• Under-cabinet lighting for kitchen tasks

• Exterior-rated fittings for outdoor areas

  
  

The goal is comfortable, useful light, not just a ceiling full of LEDs.