Monday, December 24, 2012

The Cost of Lights

So, I was at Costco, and there was a sale on LED lights.

I'm a geek. I am to LED's like a moth is to a flame. They're efficient, They're quick to react (so... they're efficient), they run cool (again... meaning they're efficient) and they are also new and shiny  and I impulsively bought them, without doing any research, because... well they were on sale.
My Light bulbs used to look like this... 

My House as a TON of GU-10 Socket light fixtures.
They are 110 Volt fixtures with 3-4 Halogen "Projector" bulbs in them.
These bulbs run HOT, don't last very long, and are high wattage for their size.
I chose to replace all these with the LED's. It meant leaving Costco with over 140 bucks in LED lights.

It seemed like a good idea at the time!

I had also gotten my first "lunker" of a hydro bill.
(Yes, Sometimes my spending habits make no sense - Big bill I have to pay = sink money into LED light bulbs?)

So,  Lets figure out how stupid I really was.

Here will be my calculations on how much you can save/spend on various forms of lighting.

First a 40 second intro to Lighting: (more if you are a slow reader)

There are 5 kinds of lighting that are commonly used in house holds.

Incandescent - Thomas Edison style - Tungsten filament, burning so hot it glows. Standard for the last century until the last decade or so. 40-60-100 watt bulbs are standard

Standard Socket Compact Florescent - Ballast built into Bulb, Direct replacement for most incandescent bulbs. 7-8 watt replaced 40. 13-14 watt replaces 60. 23-27 watt replaces 100 watt. Variety of "color" temperature, but effects useful light output. Bulbs also decay and lose up to 40% of light output with age.

Florescent Tubes - In houses, used in workshops, laundry rooms and sometimes kitchens. Bright, uniform light reduces shadows. 32-40 watts per bulb, usually 2-4 in a fixture. Somewhat harsh light, and is avoided in "living" area

Halogen Lights - Small, High output bulbs, also used in pot lights, Under cabinet lights, some desk lamps. They run hot, and burn out frequently, but are great when small size matters. 20 watt For desklamps/cabinet lighting, 35-50 watts for flood or spotlight type fixtures, 100-150 watts for outdoor / some bathroom fixtures

LED Lights - Popularized probably by Christmas lights, only in the last few years has the technology been developed to get this at a price range people will consider buying to replace normal house bulbs. More efficient than all of the other light types, they're also more expensive for the light output produced.

Heres a handy chart for Light output vs Energy Usage: (shamelessly stolen from wikipedia)

Electrical power equivalents for differing lamps[27]
Minimum light output (lumens)Electrical power consumption (Watts)
IncandescentCompact fluorescentLED
1,1007518–25Not available
1,60010023–30Not available
2,60015030–52Not available

So - Lets find out how much money I wasted:

Note: the way I will explain this wont' make sense from a science perspective, but WILL get you the desired result in energy consumption.

To calculate the cost, you need to figure out how many watts (Watt Hours) you use.

Basement - 3 Bulbs, 5 hours a day  = 750 Watts
Kitchen - 3 Bulbs, 4 hours a day = 600 Watts
Breakfast bar - 3 bulbs, 6 hours a day = 900 Watts
Bathroom - 3 Bulbs, 1.5 Hours a day = 225 Watts

Total daily usage: 1475 Watt Hours, or 1.475kWh

My Blended Usage Rate (an average of what I pay per kWh, based on time of usage peak/low rates) is about 8.3 cents per kWh (I pay 12 cents at "peak" time, 6.9 cents at night/weekends)

So, in One day, these bulbs cost me an average of 12.24 cents.
Over a year, that means $44.68 in energy us used to run these bulbs.

The LED bulbs use just 6 watts, or just 12% of what the halogens used, so all I have to do is take 12% of the total to figure out the cost of running them for a year:

44.68*0.12 = $5.36 per year.

A savings of $39.32 a year.

This means these bulbs will pay themselves off in 3.5 years in energy costs alone.

Now, there are some tangible and intangible benefits over the next 5 years of ownership:
  • The Halogen bulbs burn out quickly - I had 2 burn out in 3 months. Normalize that a bit (I might have been unlucky) and lets call it 5 a year. That's 20 dollars a year in bulbs. The LED's will last a lot longer, (probably longer than I will own the house - 5+ years.  The bulbs have a 3 year warranty to boot. so thats now $59.32 a year savings.
  • The halogens were HOT. So much so, they'd heat the back of my head when i was cooking in the kitchen. They'd also heat the basement up a bit. So the AC was turned up to counteract that. Its hard to put a dollar value on it, But I'm assuming the opposite effect occurs in winter - Gas consumption vs Electric - we'll call it a wash - But it was DEFINITELY noticeable in the fact that the kitchen has cooled off since ditching 300 watts of lights!
So, really, ~$60 a year in savings, I didn't have to replace 4 light fixtures ( 300+ Dollars)

Overall... I'd call it a "smart" decision in hindsight. 

Within the length of their lifetime, they will pay themselves off two to three times.

I am also impressed with their light output, the color and "crispness" of their light, and overall aesthetics  I'm not a huge fan of CFL (twisty) bulbs, but Use them where I can over incandescent, just for the energy savings.

When We first bought the house, almost every fixture had 60 and 100 watt incandescent bulbs (mixed randomly)

For shits and giggles one day in September  I turned on all the lights for an hour, and Documented that the house used 4.4kWh.  I turned off all the lights for an hour afterwards, and the house consumed 0.9kWh This tells me I have 3100 watts worth of Light!  I know for a fact now I've reduced that by about 1000 watts via LED and CFL lights, so Once I'm done swapping out all the bulbs, I'll do the test again (after getting a "baseline" hour) and see what the difference is!  I'll do this in a few weeks.

So my official recommendation:

If you don't mind the "light" that comes from CFL bulbs, they are the cheaper way to get energy efficiency. If you have some unique/unusual fixtures that use the two pin GU-10 sockets, LED may be the only way for you to go green - And if it is, I HIGHLY recommend it. They're great little bulbs!

1 comment:

  1. Alex, only you would do all the calculations necessary to figure out how much your impulsive purchase cost you or saved you, LOL!! Love it!