There are guidelines on how many fluorescent lights are needed in a garage to provide proper lighting. How many depends on your usage of your garage. If all you do is drive your car in and out of your garage, one large incandescent light will probably be enough. However, if you store items there, work on the car or perform other tasks in the garage you should probably opt for cost efficient and energy efficient fluorescent lighting.
Know your lighting needs
Determine your desired lighting. Accent lights highlight features like decorative wall paintings, while ambient light provides overall illumination. If you're going to do more than park your car in the garage, you want task lighting.
A standard 2-tube fluorescent light fixture may suffice if you do not use your garage a lot -- a common tube used in garage lighting is a 1.2 m (4 foot), 54-watt fluorescent. But if you have a workbench, shelves and corners, you want multiple fixtures. To get an estimate, consider a 21 watt fluorescent per square metre (2-watt per square foot) of your work area.
Depending on the size of your garage, you may want an intensely bright space. To illuminate a 6.6 m x 6.6 m (22 foot x 22 foot) area would require eight or nine, 32-watt, T8 lamps. If you want the garage to have even illumination, reduce that amount by half. Four, 3-lamp fixtures should achieve even lighting over nearly all of the garage. If you don't need to have the whole garage lit up, one or two of these fixtures should suffice.
If you perform work in your garage, do a test. If the lighting is dull in the areas where you work, add fixtures until you achieve a satisfactory level of lighting to perform your tasks. The Illuminating Engineering Society handbook provides additional information on how much lighting you need for various tasks.
If you're not sure of your lighting needs, talk to lighting experts. Provide them with your lighting needs, garage size and ceiling height. A specialist can design a layout and provide specifications on what you want: how many lumens you will get from each lamp, the spread that each light gives at each ceiling height and how much overlap to allow to achieve your desired results.