You must first find out if the fixture is safe with a 100w bulb. Makers of lighting fixtures usually specify the maximum wattage of a fixture. (See writing which is usually printed on a label, or on the fixture itself, near where the bulb is inserted.) If the fixture is rated for 60w, to be safe you need a new fixture installed that is rated 100w because the 60w fixture is very likely to overheat if you put in a conventional 100w incandescent bulb. Another solution: you could use one of the latest types of Compact Fluorescent Lamp. They use only about 1/5 (a fifth) of the power taken by an incandescent lamp. So you could have the equivalent of 100 watts of light and it would only cost you 20 watts worth of electricity! Also, a CFL should last much longer than an incandescent lamp. Five years' life is not at all unusual, compared to one year or so for an incandescent. One problem might be if you cannot find a CFL that will easily fit your present fixture. In that case why not change the fixture? Its cost might even be more than covered by the savings in electricity you might make using a CFL for the next five years and onwards, especially if you can install the new fixture yourself. Having said all that, the actual money savings you might make using a CFL will depend on the amount of time the lamp is likely to be used each day. However, now that the prices of CFLs are rapidly coming down because of the increased public demand for them - so more manufacturers are making them - the actual average daily usage time needed to save money using a CFL is becoming less and less nowadays... As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed.
Before you do any work yourself,
on electrical circuits, equipment or appliances,
always use a test meter to ensure the circuit is, in fact, de-energized
IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB
SAFELY AND COMPETENTLY
REFER THIS WORK TO QUALIFIED PROFESSIONALS.
About 150 watts.
The formula you are looking for is W = I x E. Watts = Amps x Volts. If you can find the two values on the fixture's label then use the formula to find the wattage of the fixture.
Look at the wattage capacity of the fixture. Some fixtures are limited to 65 watts, some can take much more. If you use a larger bulb than what the fixture was designed for you create a fire risk. If you need to use a larger bulb but the fixture is limited to 65 watts, you need to change the fixture.
Unless it's in a palace, a bathroom probably won't need more than 240 watts in total, if they are incandescent bulbs, or 40-60 watts for CFL bulbs. Try four 15 w spiral CFLs. My bathroom is a small one with a 70 w halogen bulb.
Depends if ballast is in fixture and switch is on. Several watts if new ballast and perhaps 15 watts for old ballasts....
If a fixture is only rated for 75 watts and you install a 100 watt light bulb in it, you have exceeded the rating of the fixture. The fixture could overheat and catch fire. Do not do this! electrical equipment have been tested to see what they can safely handle.
NEVER! NEVER! NEVER! The current draw from a 100W light greatly exceeds the design limits built into the 60W fixture. The end result would be a fire. You can use florescent light bulbs to get more light with less amperage. You get 100 watts equivalent lighting for 23 watts and will not create a fire hazard.
The fixture recommended wattage is a maximum limit. Using a smaller wattage bulb is fine.
The watts determine how much energy is taken and how much heat is produced. You need to look at the lumens to see how much light is produced. CFLs produce 4-5 times more lumens than incandescent bulbs, or 3-4 times more than halogens, for the same power in watts.
How many watts a bathroom exhaust fan uses will depend on the fan used. Some can use up to 60 or more watts, while other more energy efficient models could use as little as six watts.