How much effect does dimming/running a light on lower output have on its electricity usage?

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Downey_Mildew

New Member
I'm in the process of looking at indoor equipment and live in a country where electricity is not exactly cheap. I was wondering if I'd be better off buying a LED growlight that is higher wattage, slightly more efficient (higher quality bar setup) and pay a higher price for it up front if it means I get to run it at lower power/dimmed values. The rationale would be to have a higher quality light whileusing less electricity, increase longevity of the light and make up for the higher initial purchasing price in X years.
However, does running something at lower power/dimming decrease the electricity it uses by an equal amount?

I was wondering if anyone can educate me through the following hypothetical scenario:
If a 1000W LED lamp is dimmed/run output at 50%, then 500 Watts will be used for the plants. Does this also mean the light uses up 50% less electricity at that moment? Would it be correct that a 500W LED light run at 100% output with the same efficiency as a 1000W light run at 50% output uses equal amounts of electricity if all other variables (efficiency etc) are equal?

I run into the same dilemma when choosing between 6" Inline Duct Fans versus 4'' Inline Duct Fans. The 6'' have more wattage so should theoretically use more electricity, however how much of an impact does it make if the 6'' version is only slightly more expensive up front and will let me run it at half power most of the time as opposed to a 4'' at 100% power.

Anyone that can shed some light on the topic? Any info is much appreciated!
 
hotrodharley

hotrodharley

Well-Known Member
Buy the most powerful light you can squeeze into your grow space. Make sure it’s dimmable. Buy a decent quantum PAR meter for less than $200. It will quickly pay for itself. You’ll save money on electricity.
 
hotrodharley

hotrodharley

Well-Known Member
Variable speed fans are also good. However I’ve found the 4” are good for an intake. 6” at full speed for exhaust.
 
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Downey_Mildew

New Member
Thank you for your input. Do you have any insight about the relationship between running a lamp at lower power/dimming and the actual power draw change? Running a lamp at 50% brightness does not result in an equal 50% reduction in power usage does it? Would have to get an outlet wattage meter to see the actual power draw, I wonder how much it impacts it.
 
Boatguy

Boatguy

Well-Known Member
Downey_Mildew said:
Thank you for your input. Do you have any insight about the relationship between running a lamp at lower power/dimming and the actual power draw change? Running a lamp at 50% brightness does not result in an equal 50% reduction in power usage does it? Would have to get an outlet wattage meter to see the actual power draw, I wonder how much it impacts it.
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It results in lower efficiency from the driver. Meanwell's driver documentation shows how efficiency changes based on dimming.
Measuring power draw wont tell you whats going on there. The best plan is to get something alittle over powered, not majorly, and dim as you see fit for veg and flower.
 
Horselover fat

Horselover fat

Well-Known Member
Dimming the fixture makes it more efficient per watt, but how much more efficient depends on things... Your diodes will become more efficient, because they will be cooler and cooler diodes are more efficient. Your power supply however will work at a lower effiniency when it isn't running at full steam. How much less efficient depends on the driver.

Here is an example of how a set of diodes would respond to current. These are just diodes without consideration for how the power supply affects things.

CurrentLumenLumen/W
0.350 A3005 lm233.13 lm/W
0.700 A5968 lm227.79 lm/W
1.050 A8868 lm222.93 lm/W
1.400 A11714 lm218.59 lm/W
1.750 A14492 lm214.38 lm/W
2.100 A17239 lm210.75 lm/W
2.800 A22574 lm203.85 lm/W
3.500 A27633 lm197.53 lm/W
 
coreywebster

coreywebster

Well-Known Member
In my opinion you are over thinking it.

Buy a light that covers your area well and is a bit over what you need.. not double what you need because the price difference isn't worth the small gain in efficiency.

As for fans, they are low power in comparison and don't cost much to run.
But you should buy one sized for worst case (hottest summer days) and run it slower for most of the year.
 
lusidghost

lusidghost

Well-Known Member
Downey_Mildew said:
I run into the same dilemma when choosing between 6" Inline Duct Fans versus 4'' Inline Duct Fans. The 6'' have more wattage so should theoretically use more electricity, however how much of an impact does it make if the 6'' version is only slightly more expensive up front and will let me run it at half power most of the time as opposed to a 4'' at 100% power.
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Fans don't use a lot of power, but AC Infinity Cloudline fans are automated to kick on and off when temps or humidity get high. You'll definitely save electric. Especially when the lights are out. It will also save on heating in the winter by not throwing warm air out of the house 24/7.
 
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Phytoplankton

Well-Known Member
Downey_Mildew said:
I'm in the process of looking at indoor equipment and live in a country where electricity is not exactly cheap. I was wondering if I'd be better off buying a LED growlight that is higher wattage, slightly more efficient (higher quality bar setup) and pay a higher price for it up front if it means I get to run it at lower power/dimmed values. The rationale would be to have a higher quality light whileusing less electricity, increase longevity of the light and make up for the higher initial purchasing price in X years.
However, does running something at lower power/dimming decrease the electricity it uses by an equal amount?

I was wondering if anyone can educate me through the following hypothetical scenario:
If a 1000W LED lamp is dimmed/run output at 50%, then 500 Watts will be used for the plants. Does this also mean the light uses up 50% less electricity at that moment? Would it be correct that a 500W LED light run at 100% output with the same efficiency as a 1000W light run at 50% output uses equal amounts of electricity if all other variables (efficiency etc) are equal?

I run into the same dilemma when choosing between 6" Inline Duct Fans versus 4'' Inline Duct Fans. The 6'' have more wattage so should theoretically use more electricity, however how much of an impact does it make if the 6'' version is only slightly more expensive up front and will let me run it at half power most of the time as opposed to a 4'' at 100% power.

Anyone that can shed some light on the topic? Any info is much appreciated!
Click to expand...
To answer your question, yes, dimming will decrease the power consumption. It not quite a straight line conversion, but it’s close. Also railing your lights (full power all the time), can hasten driver failure.
 
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