The best choice (2017) is now LED and traditional bulbs will gradually phase out over time. Fortunately there is an LED equivalent for all types bulb of so the light fittings designed for traditional bulbs can still be used.
If you decide on LED you will wonder why some people have the cheek to charge twice or more than you can buy LED bulbs on EBay. Like anything if it is cheap the quality suffers because it is unlikely that the seller is working for no profit. With an LED it will be in the quality of the chip and/or the electronics. No real way of telling the quality of the chip until time has passed. You can tell if the quality of the electronics is low budget as the LED's will have a flicker. This is not detectable with the naked eye, but shows up when viewed through a phone camera.
If it flickers save yourself a headache and don't buy it.
All the bulb types below are still available in NZ but some types such as incandescent candles are becoming hard to get.
These are often called General Lighting Service (GLS) lamps and are the least efficient. They will produce about 15 lumens of light for every watt of electricity used.
Incandescent or GLS lamps can be dimmed (ie run on a lower voltage). When the rated voltage of a lamp is reduced (by dimming), the light out put and colour temperature are lowered. Running a lamp on lower than its rated voltage will also increase its life. Conversely, running a GLS lamp on a higher than rated voltage (over-voltage) will shorten its life. Over-voltage and over-current are the most common reasons for GLS lamps failing. This often occurs when lamps are first switched on and the current rises rapidly (over a few milliseconds) or when variations in the supply voltage causes it to rise above 230volts.
These lamps have a life of about 1000 hours
CFL Compact Fluorescent Lamps
These lamps will produce the same light as an incandescent lamp but require only 20% of the power. They can do this because less energy is wasted in heat. A CFL can be used to replace either bayonet or Edison screw bulbs.
This table shows the equivalent wattages of Osram Duluxstar Twist and incandescent lamps.
For comparison a CFL lamp produces about 60 lumens of light per watt of electricity used
Compact Fluorescent Wattage
The twist bulbs are more efficient and smaller than the u shaped bulbs and will fit into any light that uses an incandescent bulb.
The average life of an Osram Duluxstar bulb is about 5000 hours but lower quality bulbs can be much less.
12 volt halogen bulbs are usually of the MR16 type. The MR stands for multi faceted reflector and the 16 for the diameter of the bulb in one eighths of an inch i.e. two inches or 50mm. Halogen bulbs that operate on 230 volts or 110 volts are the same shape but the pins on the base are of the twist and lock type and cannot be inserted into a 12 volt fitting.
A halogen lamp will produce about 35 lumens per watt.
bulbs are available in four beam widths. The ten and 24 degrees are used to give a narrow spot beam, the 36 degrees is most common domestically used for floodlighting and the sixty degrees is becoming more popular for general floodlighting.
Osram Infra Red Coating Lamps
(IRC) are about 30% more efficient than normal halogen lamps. They achieve this by making better use of the heat generated.
A low voltage halogen lamp has a life of between 2000 and 5000 hours depending on the quality. A mains voltage lamp will last 2000 hours
Fluorescent tubes are specified by their wattage and diameter. The diameter is given as T and a number. The number is the diameter of the tube in one eighths of an inch.
ie a T4 tube is half an inch in diameter. Common tube diameters are T4, T5 and T8
The wattage of the tube determines its length, so if you buy a tube of the same wattage it will fit into the light.
The tubes are available in a range of colour temperatures which range from warm white to cool white and daylight.
These lamps are very efficient and produce about 70 lumens per watt, they have a life of about 10,000 hours.
Types of Bases
The base of the lamp makes the electrical connection with the with the light fitting and there are a wide variety of different bases.
Theses are the more common bases:
Incandescent and Compact Fluorescent.
Bayonet fittings are the push and lock type and come in two sizes. The most common is B22d which is 22mm in diameter and the small bayonet B15d which is 15mm in diameter.
The screw bases are called Edison Screw and there are two sizes in common use.
The E27 is the most common and has a diameter of 27mm. The Small Edison Screw (SES) or E14 has a diameter of 14mm.
Halogen Lamps 12 Volt
Halogen capsules have pin bases. The number refers to the distance the pins are apart,IE the G4 has pins 4mm apart. These are the common sizes in use in NZ
The MR16 12 volt reflector lamp base has two pins and the number 16 refers to their distance apart in millimeters.
Halogen Lamps 220 to 240 Volts
These lamps have two pins with a larger diameter end which allows them to twist and lock into the fitting.
The most common type is the GU10 which has the pins 10mm apart.
Mains Voltage halogen capsules have a G9 base;