What does lumens mean in solar lights?

What are lumens?

Lumens are a measure of brightness, denoted by the symbol “lm”. In simple terms, a lumen rating tells us the total amount of visible light given off by a light source. Lumens are useful because they give us a standard metric for comparing the brightness of lights, something that has become necessary as light technologies have evolved.

Watts or lumens – which is better?

Until recently, when we bought lights most of us used watts as our guide to the brightness of the light. But watts are not a measure of brightness. Watts are a measure of the amount of energy consumed by the light.

In previous times when almost all lights used incandescent bulbs, watts – i.e. energy consumed – was a valid number for comparing brightness. However, energy efficient alternatives to incandescent lights, including LED (light emitting diodes) and CFL (compact fluorescent lamps), are changing the game. Because LEDs and CFLs are vastly more efficient than incandescent lights, energy consumed is no longer an appropriate metric to use when comparing the brightness of lights.

So lumens keep it simple by measuring what we actually care about – brightness.

Converting watts to lumens

If you find yourself needing to estimate the brightness (lumens) of an incandescent bulb quoted in watts, here is a conversion chart:

How many lumens do I need for outdoor solar lighting?

That will depend on what kind of outdoor lighting you are installing.

Step lights

Typical rating: 12 to 100 lumens

Step lights (or stair lights) are intended to prevent falls on an outdoor staircase. They don’t have to be particularly bright, but they do need to show the way clearly and unambiguously. This means avoiding shadows or lighting gaps, and so it is better to have a larger number of smaller lights than a smaller number of brighter lights.

Path lights

Typical rating: 100 – 200 lumens

Path lights guide you and your guests, and they also add a decorative touch to your yard or garden. They are spaced farther apart than step lights and so a little more brightness from each light is desirable.

Landscape spotlights

Typical rating: 50 to 300 lumens, some as high as 600

Small shrubs can be lit up nicely from below by a 50 lumen landscape spotlight. 

If you’re wanting to illuminate larger features of a yard or garden, then a brighter light is appropriate. These are often sold in sets of two or four. For example, Urpower spotlights come in a set of 4 x 220 lumens. Another popular choice is the Litom 2 x 600 lumen landscape spotlights. You can learn more about both of these here.

Having a set of two or four spotlights is nice because it lets you easily play with different lighting arrangements.

You might choose to light a certain tree from the left and right. Or, if you need more brightness falling on one location, you could place a pair of these lights close together.

And because solar lights can easily be moved to a new location – no underground wiring, no unsightly cords – you are free to experiment with different configurations and placements.

Flood lights and motion sensing security lights

Typical rating: 300 lumens for a small area, 700 and up for larger areas

Flood lights are not meant to be gentle. These are big, bright lights designed to light up a large area, either for security or to help you see what you’re doing.

At the smaller end of the spectrum, you might position a 300 lumens motion sensing light around a doorway. That’s enough to help you find your keys and get them into the lock. Whether it is adequate for security will depend on the specifics of the location.

If you need to light up a larger area then you’ll want a flood light with a lumen rating of 700 or even more. Some models are capable of throwing off 2000, 3000 or even 5000 in the brightest models. This would be overkill in a small secure space, but is appropriate to provide illumination over a wider area.

Lamp post

Typical rating: 120 to 180 lumens

Lamp posts look classy and throw off useful light, but they don’t need to be as bright as a flood light. And they fact that the post raises the light well above the ground means that even a 115 or 130 lumen light can illuminate a much wider area than a path light.

Are watts still a useful metric?

Not for buyers of solar lights. Watts are still a useful number for electricians or homeowners deciding how many and what kind of lights can be combined on a circuit. And of course your electricity provider needs a way to measure how much power your home is using and they will continue to rely on watts as their key metric.

But for a solar light, your main concern is, “How bright is this light?” And to answer that question, lumens are the way to go.

What about candlepower as a measure of brightness?

Candlepower is useful when discussing or comparing flashlights, but less so with solar lights. We’ve all noticed that the light emitted by a flashlight is brightest at the center of the beam. Candlepower is concerned with the measurement of this center-of-beam brightness, rather than all of the other light around the periphery. Lumens, on the other hand, is a measure of the total visible light emitted. Here is a useful guide to the difference between lumens and candlepower.

Wrapping up

We began with the question, “what does lumens mean in solar lights”? And now you know that lumens are the most useful way of measuring and comparing the brightness of solar lights. And you also have some idea now of the appropriate number of lumens for different kinds of lights. Thanks for reading.

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