We have been comparing the electricity incandescent light bulbs consume compared to compact fluorescent (CFL) light bulbs.

In our posting Do Compact Fluorescent Bulbs really Save Energy we show a detailed graph of the energy used for each bulb or device in our apartments two bedrooms and bathroom. The graph shows the electricity consumed as each light bulb and appliance is switched on, first the incandescent bulbs, and then the replacement CFL bulbs.

I do encourage you to look at the article to see how much energy the CFL bulbs save. The data is real, and the replacement bulbs were carefully selected to give out exactly the same amounts (lumen) of light as the old incandescent bulbs.

We continued with our monitoring, this time to measure the actual electricity used by us over two week days. Monday and Tuesday were monitored using the old incandescent bulbs, Thursday and Friday were monitored using the new CFL bulbs.

Here is the graph of the four days of data, monitored using a watts up Smart Circuit 20





X Axis - Time
Y Axis - Watts

Once again the data speaks for itself.

We are saving more than 50% of the electricity we used to use for our bedroom(s) and bathroom electricity consumption.

As with all things there is a but .........

CFL's do contain a trace of mercury, see The truth about Energy Saving (CFL) Light Bulbs where we write "but the mercury is sealed within the bulbs glass tube and is of no danger at all. The amount is less than four milligrams, about that required to cover the tip of a ball-point pen. Given the amount of fossil fuels incandescent bulbs waste, your CFL's will be saving both mercury and many other toxic chemicals required to produce the excess energy" Notwithstanding, be responsible and dispose of them as directed.

Individual CFL's have a Power factor of between 55% and 70% (the actual power factor on the circuit during the above testing was 100% for the incandescent bulbs and 85% for the CFL bulbs) If ever there was a confusing topic filled with FUD (Fear Uncertainty and Doubt) this must be high on the list.

It might help if we first agree on some terms. See this summary for an explanation of real power, apparent power, reactive power and power factor. The article has a link to Wikipedia for those who want an even more detailed explanation.

A low power factor means that energy is being supplied by the grid and then not used by the device – but the energy is NOT wasted. The energy is returned to the electrical circuit and from there to the sub-station, incurring distribution and harmonic losses, in the order of 1%.

There are complicated discussions on how consumer and industrial users are billed for having a low power factor. In addition to the distribution losses there are implications to how much power the energy company needs to supply. At peak loads the utilities do not want to be producing electricity that is not fully consumed. Unfortunately they have to deliver 100% of the demand, even if the devices return a large portion of it through low power factor.

Every utility has a different rule, depending on the implications to them of a reduced power factor. I mention circuit for there are two types of power factor loss, that caused by electrical inefficiency, and that caused by the back resistance of a motor. In a home we create both, the fridge creates a back current when to compressor runs, and it may be on the same circuit as a CFL – it is quite possible that the two cancel each other out (electricity is a wave) and there is an advantage to having a CFL with a low power factor

In California there is no charge to consumers for low power factor. The consumer is only charged for the active power, what you used. This is because compared to industry, in the same sub-station, commercial power dwarfs the consumer issue. Commercial companies are penalized for a net power factor of less than 85%, and given incentives for being higher than 85%.

I stop here, for it is quite impossible to determine what the billing implications or electricity implications of a lower power factor are in a specific instance, let alone at a general level. I know that PG&E are subsidizing the supply of CFL bulbs, so we have to assume THEY THINK it is a net positive?

With that out the way, back to the energy saving.

CFL’s give off less heat than incandescent bulbs, for the same Lumens of light. This is why they use up to 75% less electricity. If you are in a cold climate, you could argue that the incandescent bulbs are no less efficient for their extra energy will be less heat to create.

I am not making this up, it was argued to me once. It is not a good argument though, for they are not good heaters compared to other natural gas burning heaters.

The combination of a longer life, and the energy you will save justifies investigation into CFL lighting in almost all situations. This is particularly true for outside walkways and home entrance lighting. These bulbs are on for 8 hours each day and I can see no reason not to replace them.

I encourage you to visit the web site of Wholesale Bulbs who have a comprehensive catalog, and direct from manufacturer pricing for Energy Star certified CFL bulbs.