Lighting
25% of Domestic Electricity Use – Potential Savings: $100 per year
(Based on replacing 10 x 60 watt bulbs with 10 x 15 watt compact fluorescent (CF) lamps; lights on 6 hours per day x 365 days; electricity cost $0.10 per kWh)
The light bulb was the first commercially available electric appliance. In fact, many electricity suppliers are still known as “Power and Light” companies. It is the simplest and cheapest appliance you can buy. Lighting is also the most affordable energy efficiency investment, yielding the best return. The incandescent light bulb was invented over 140 years ago. It is time to relegate it to museums, or to special uses where nothing else will do.
Incandescent
Incandescent lamps work by passing an electric current through a fine tungsten wire, which gets hot and glows. The bulbs used to be evacuated so there would be no oxygen inside to oxidize (burn) the filament. Today they are usually filled with an inert gas. The more current flows through the wire, the hotter and brighter it gets. That is important – increased heat gives more, whiter light, but high temperature also causes the wire to vapourize more rapidly, shortening life. “Long Life” bulbs tend to run at a lower temperature, and give less light than standard ones.
Light is a good example of a service provided by electricity. With lighting we want lumens (a measure of light intensity), but pay for kilowatt hours. The right choice of lighting equipment can give you the lumens you need for far less power, and money.
Gas Discharge
All industrial and municipal lighting is now provided by gas discharge lamps. These pass current through a gas, which ionizes and glows. Most of these lamps produce colours few of us would want at home. Neon lamps glow bright red and are used in advertising. Sodium lamps produce a brilliant yellow, excellent for street lighting. Mercury lamps give a greenish-blue, but are rare now due to their relatively low efficiency and mercury content.
Fluorescent
The majority of gas discharge lamps are fluorescent tubes. Their gas glows to produce invisible ultraviolet radiation. Fluorescents are very versatile because the inside of the glass tube is coated with phosphors. These absorb ultraviolet, re-radiating this absorbed energy as visible light. Manufacturers choose the colour their fluorescent tubes produce. Most of the colours used in advertising are fluorescent lamps with special phosphors. Offices and large stores are lit with “cool white” fluorescents. Boutique shops and homes prefer “warm white”. Industrial premises use “daylight” which is noticeably blue.
Compact Fluorescent
Fluorescents are far more efficient than incandescents. For example, a 100 watt incandescent lamp yields 1550 lumens. By contrast, a 40 watt fluorescent tube (4 foot) yields 2500 to 4000 lumens. Some 25 years ago manufacturers developed the compact fluorescent (CF) with a thinner tube (like your little finger). This is coiled into a compact shape and mounted on the same base as an incandescent bulb. CFs are now small enough to fit most light fixtures. They are generally 12-25 watts, with the light output of 50-100 watt bulbs. CF lamps as small as 5 or as high as 36 watts are available.
Over a ~5 year life, a compact fluorescent (CF) lamp, on for 5 hr/day, saves enough to buy 5 more. CF lamps often outlast manufacturer’s claims, saving even more. In 14 years, I have replaced only a ½ dozen of the 40 in my house.
CFs are more costly than incandescent lamps and should be put into high use fixtures where they will give the best savings. Outside lights at the front of a house are a good choice. These are often left on overnight, and sometimes the following day – a good opportunity to save electricity. Make sure that your choice will work in winter cold.
Most CF lamps are destroyed by dimmer switches! Dimmer-compatible CF lamps are available, but expensive. You can also buy “Tri-light” CF lamps with 3 intensity levels – also expensive.
Halogen or Quartz
Another widely available choice is the halogen or quartz lamp. Quartz-halogen lamps were originally (in 1968) developed for car headlights. These are incandescent lamps filled with a halogen gas (iodine, chlorine, etc) and a far smaller envelope (bulb) made of quartz -so it doesn’t melt. The gas and hot quartz envelope slow tungsten loss from the filament.
Halogen lamps can either offer more light or longer life than ordinary incandescents. Their slightly longer life does not compensate for a price close to that of a CF lamp.
They are usually bought as a decor statement. They are very good for task lighting where tiny reflector lamps (10-20 watts) light a small working area very well.
The “Earth Light”
A widely available incandescent light bulb labeled “Earth Light”, packed in enviro-green boxes claims to save energy. “Earth Lights” are NOT energy efficient! They are offering a 90-watt lamp to replace 100 watts. Certainly, you use less energy, but you also get less light! If you insist on going that route, replace your 100-watt lamps with 60 or even 40-watt ones for “romantic” lighting. A 40-watt bulb uses 2 ½ times the energy of a 15-watt CF – but provides less than 1/3 of the light!