I asked Reliance Controls about a THP103 meter that I was having trouble with. Turns out that it's not a true RMS meter and thus is unable to give you accurate readings on a CFL or LED installation. See my other question: Why am I getting strange results when using a power meter to measure CFLs?
After explaining why I was testing a CFL (not seeing a noticeable difference in the cost of electricity being used) they replied with the following which I'm assuming isn't public knowledge because the average person doesn't have a degree in Electrical Engineering:
You may already have information on estimating the energy usage/utility charges, but here is a document that might assist in calculations if you are interested. The difference between a 100W incandescent light and a 15W CFL is pretty minimal when related to monthly costs, but that's just a generalization and there are many factors.
If both lights are on 24 hours per day, for 30 days in a month, the 100W bulb might cost about 5-6$ more for that month than a 15W CFL. But if they are on only 12 hours per day, for 30 days, the difference is much less, maybe only 2-3$ per month. Less than 12 hours per day will bring that difference closer as well. Maybe some of the formulas will help learn more about what could be bringing the bill up or down.
So, I'm looking for a way to bring down my electric bill and I'm leaning on the age old principle of simply turning off the lights when you leave the room. However, I work long hours and light is somewhat of a necessity unless I work by the glow of my computer screen. Plus I need a light for my chickens which require 16 hrs of light during the day and winter is setting in, and the simple fact that I live with 3 other people who don't know how to turn off the lights. One's 3 so he's excused until he can reach the switch.
Does anyone know if LED bulbs make any difference in terms of lowering costs to a noticeable degree?
Best Answer
Say your electrical bill is $100 a month.
Now say you have a refrigerator, a computer, a window fan and your light bulbs in your house as your only electrical devices. Everything but your light bulbs are on 24/7.
In that scenario your lights represent 0.8/24.8 or 3% of your daily electrical consumption.
If you replace your light with a 15W bulb, you've dropped from 24.8kWh to 24.12kWh a day, a savings of only 2.7% of your total daily consumption.
Addendum: I am not saying lighting is going to be 3% of your bill - I'm only making an example. You have to do the math - you have to figure out how much total power you're using (check electric bill) and then how much power your lights use (look at the bulbs and measure how long each one is left on each day) and that's your total % of energy for lighting. If that % is 15 then you can only reduce that 15%. You can cut your lighting costs in half, but half of 15% is only 7.5%.