My boat had 4 lamps mounted around the cabin and galley that use screw in bulbs that are 12volt but look like household bulbs. The fixture is like this:
And have shades on them like this:
They put out very decent light, but with 15 and 25watt bulbs they sucked a lot
of battery juice. I replaced the bulbs with screw-in 12volt compact flourescent lamps that cost about $7 each through an online RV supply store. They come in varied color temperatures and I selected one step warmer than tungsten (but still well below daylight). They worked out great! Use about 25% of the power of the tungsten. Only difficulty was getting the shades to fit. They are designed to grasp a round bulb, not the curly CFL bulbs. But with some finagling I got them to hold on.
For specific use lighting (reading, focused, etc) I have begun switching out the 12v tungsten and halogen bulbs for LED's. There are an ever increasing variety of "bulbs" available with the proper base/contacts arrangement to fit the existing fixtures. For spot use there are white (not bluish white) bulbs that fit right into the existing brass bell fixtures. (But I do not
do this where I need dimmable lighting, as LED's require special dimmer circuitry.)
Up forward there are two "steerable" spots on the bulkhead that take 25watt tungsten bulbs of the "spotlight" (or "mushroom") shape with a very long neck. A lot of directed light, but very hot
, and use a lot
of power. I finally found LED bulbs with the single contact base the fixtures need. The replacement arrays fit way down inside
, as they are short neck not long, but are very bright though not quite as wide a spread of light, and use minimal power. Very minimal.
In the head there is a fixture that is rectangular with a white plastic cover for top and sides, and has two tungsten bulbs inside. Similar to this but angles instead of curved cover:
I replaced the bulbs with two 36 LED "bulbs". They are slightly less bright, but distinctly cooler than the tungsten. I think I will probably go back to tungsten as the head lighting is not used for long times. Otherwise I will go with a CFL screw in fixture like the main cabin.
In cupboards and hanging lockers I have 6 inch flourescents that are powered by 4 AAA batteries (which, since they are only on for short periods, last a long time).