LEDs and electricity savings

[sphelps]

Oh no another LED thread to discuss electricity savings

Actually I just wanted to share some results I recently measured. Not long ago I wondered how much power I was actually saving with LEDs compared to a lighting source such as metal halides. One of primary reasons many of us make the switch is the potential for such savings, among others, but some of us have often wondered if the savings are that substantial when you consider your heater may have to work a little harder to combat those "cooler" LEDs. So I decided to measure the power consumption of each and see exactly what I'm saving. I'm sharing the results more for "food for thought" purposes, everyone will get different results and may make different assumptions than me.

Executive Summary:

• LED power used: 0.84 kWh per day
• Metal Halide Comparison: 6.12 kWh per day
• Heater power saved from Halides: 0.91 kWh per day
• LED power savings: 4.37 kWh per day
• In this case the power saved with LEDs is substantial including the extra power requirement from heaters.

Some system details

• Display tank volume: 270 gallons
• Connected frag tank and sump volume: 70 gallons
• Realistic water volume approximation: 300 gallons.
• Maintained water temperature: 78F
• Lights: 3 x Mitra
• Heaters: 2 x 300W

Insulation and equipment heat addition:

• 15mm glass with only view-able side but has an open top.
• Sumps are acrylic and contained in a humidity controlled room which stays fairly humid and warm meaning heat loss from the sumps will be minor.
• I'll installed all my pumps internal to take advantage of their heat loss.
• I also have fridges under the main tank which vent around the sides and back.

In other words I've taken some steps to add as much heat to the tank from equipment and keep it in as much as possible without doing something that would have negative effects. I mention this because I think it's important when looking at your own tank you consider how heat loss/addition will effect your savings.

Measured Results:

• Lights run for 12 hours, peak at 135W dimming up and down. Power used per day is 0.84 kWh
• I measured the power used by the heaters a few different ways, during the full 12 hours on different days, during the peak light time and 24-7 to get a feel for any changes in usage that occur. I concluded the heaters duty cycle doesn't fluctuate substantially and they use an average of 0.13 kW per hour.

Now for the debatable part, the comparison.

• The mitras run in high output mode, GHL claims it's comparable to 340W of halide, however I would no way compare the 12 hours of ramping up and down to that of a solid state 340W halide. Rather I believe it's comparable to 6 hours of equivalent halide which is 6.12 kWh per day excluding any inefficiencies.
• In my experience when halides are on, heaters are off. I also think another hour is fair for a cooling off period. In other words I'm assuming the halides save me 7 hours of heat which is 0.91 kWh per day.

Conclusion

• LEDs save me money in electricity even with heating cost included. A total savings of 4.37 kWh per day or approximately 70% decrease. However I believe the steps I've taken to with hold heat are a key player for this savings, I've noticed the heaters activate much less frequently from switching to acrylic sumps alone. I also maintain my temp at 78F while many SPS gurus will keep it closer to 80F which could play a role as well. This of course was also a winter reading, results will be different if house temperature climbs during hot summer days. Other peoples results will vary but the substantial difference I measured should conclude in virtually all cases the electricity savings are real.