(well, energy is neither created or destroyed... Just converted to other forms. Nick

...The amount of light reaching a surface, is inversly proportional to the [square of the] distance, between light source and the surface. Bunsen's (1811) grease spot photometer is one way to compare the light output from a CF and an incandescent bulb. Put a grease spot on a piece of paper and find the position between the bulbs where the spot seems to disappear, which indicates that it is equally lit on both sides. Then measure the distance to each bulb... Nick

  Color will also affect brightness in different rooms. Different fluorescent bulbs (different models) radiate different colors.  We use terms like soft white, natural light, etc to describe bulbs with different color intensities.  Trial and error may be required. The necessity for trial and error is one of the more frustrating things about CF bulbs.  They're expensive enough (often $10+ for the better brands) that it's difficult to try one and see if you like it - any money savings is pretty much wiped out if you have to buy and discard a couple of expensive CF bulbs because they don't give the right kind of light. If you have a lot of places to use CF bulbs, then you could use the reject bulbs in places that are less important (bathroom, kitchen, etc.) but it's still a lot of hassle and expense.   Karen

Watts(power) = current(amps) X  voltage. (period)  For a purely resistive load, then there are inductive loads, reactive loads, etc. Lumens is just one measurement of light output, as are Candela, foot candles, and candlepower, just to name a few. We should never get Watts and Lumens confused. Also we have to consider whether the lamp is cool white, warm white, or clear.  There are lots of variables.

Light falls off relative to the square of the distance.  A 100 watt incandescent bulb 7 feet away will give you the same amount of light as a 200 watt bulb 10 feet away.  Or a 50 watt bulb 5 feet away. A quirk of incandescent lightbulbs is that its efficiency is a function of its temperature, so that at those distances the 100 watt lightbulb will be brighter than the 50 watt and dimmer than the 200 watt due to the temperature differences.  In other words, those silly 40 watt lightbulbs give little light in comparison with the amount of money it sucks away, and that dimming the lights may be less frugal than switching a lightbulb off.