How many watts does an LED spot need?

That has become the wrong question. Since LED, watts tells you nothing about how much light you get — look at lumens. For orientation: our recessed spotlights sit between 3 and 7 watts and give 320 to 700 lumens with it. For an average room you need spots of 5 to 6 watts.

Why watts lost its meaning

With incandescent bulbs, consumption tracked light output neatly, so you could shop on watts. With LED that link is broken: how efficient a spot is varies per model.

Two examples from our own catalog, both 5 watts:

• Marlo — 5 watts, 350 lumens
• Lyvo — 5 watts, 500 lumens

Same consumption, almost half as much light again. Buy on watts and you are shopping in the dark.

What our spots consume

The range in the catalog, with the output alongside:

• Vigo — 5 watts, 320 lm
• Marlo — 5 watts, 350 lm
• Lesto — 4 or 6 watts switchable, up to 400 lm
• Quaro — 6 watts, 400 lm
• Ferro — 6 watts, 600 lm
• Lyvo — 5 or 7 watts, 500 or 700 lm

So six watts is both 400 and 600 lumens, depending which spot you pick. That 50 percent difference at the same consumption is exactly why you have to compare on lumens.

When watts does matter

Three situations, and then it is not about light but about the electrics:

1. Your dimmer. Add up the consumption of every spot on the dimmer. Our dimmer 0.5-250W could in theory handle forty spots of 6 watts.
2. Your driver. Same sum, but per driver. Our 20-watt 12V driver is rated at a maximum of six spots.
3. Your circuit. At the fuse box power is what counts, and with LED you rarely run into that in a home.

For those three sums, watts is exactly the right number. For the question of how bright your room will be, it is not.

The switchable spots

Two models let you choose. The Lesto has a wattage switch between 4 and 6 watts, the Lyvo between 5 and 7 watts. That is not dimming — it is a fixed setting you choose during installation.

Handy if you use the same spot in two rooms: the high setting in the kitchen, the low one in the hallway. One order, two light levels, and the ceiling looks the same everywhere.

The number that actually matters

If you want one figure to compare spots fairly, divide the lumens by the watts. That is the efficiency, expressed in lumens per watt, and it tells you how much light you get per watt consumed.

Run it on our own spots: the Marlo comes to 70 lumens per watt, the Quaro to about 67, the Ferro to 100 and the Lyvo to 100. That is a fifty percent difference between the most and least efficient spot in the same catalog. Over the life of a ceiling full of spots that adds up, and it also explains why one spot costs a few euros more than another.

How to convert it

If you do want to go from watts to a number of spots: first establish how many lumens you need (roughly 100 to 150 per square meter for a living room, 200 to 300 for kitchen and bathroom), and divide that by the output per spot. The wattage then falls out by itself as a sum.

For a living room of 30 m² you come to around 3,000 to 4,500 lumens. With 600-lumen Ferros that is five to eight spots, and therefore 30 to 48 watts in total. That is less than a single old-fashioned incandescent bulb.

The calculation is worked through in How many lumens do you need per room? All the wattages and lumen figures are listed per product with the recessed spotlights.