Very little. A 10W LED downlight running five hours a night uses about 18kWh a year, which is roughly $6 to $7 at current electricity rates. The 50W halogen it replaces costs over $30 a year, so a house full of LEDs typically cuts lighting energy use by 75 percent or more.

Warm white (3000K) suits living rooms, bedrooms and dining areas. Cool white (4000K) suits kitchens, bathrooms, laundries and garages. If you are not sure, choose a tri-colour (CCT selectable) fitting and pick between 3000K, 4000K and 5000K on the fitting itself after install.

Buy on lumens, not watts. As a guide, a 6W to 7W LED replaces a 50W halogen, a 9W LED replaces a 60W incandescent, and a 13W to 15W LED replaces a 100W incandescent. Check the lumen output on the product page to match brightness exactly.

Quality LEDs are rated for 30,000 to 50,000 hours, which is well over 15 years at five hours a night. Fittings are either integrated, where the LED is built in, or take a replaceable LED globe. The product page for every fitting tells you which one you are looking at.

No. Check the product page for dimming compatibility before you buy. Dimmable LEDs also need an LED-compatible trailing edge dimmer; pairing them with an old halogen dimmer is the most common cause of flickering.

LEDs run far cooler than halogen or incandescent, but they still produce some heat. For downlights installed under ceiling insulation, choose an IC-F abutment rated fitting so insulation can safely sit against it. This is an Australian safety requirement, so do not skip it.

Yes, most LED strips can be cut, but only at the marked cut points along the strip. Cutting anywhere else will stop that section working. If you are joining or extending strips, use the matching connectors and make sure your LED driver has enough capacity for the total run.

Almost always. Switching from halogen to LED typically cuts lighting energy use by 50 to 75 percent, and several states run energy efficiency schemes that subsidise LED retrofits. Add a lifespan of 10 to 15 plus years and most homes recoup the cost of the upgrade within a couple of years.