Everyones banging on about using low energy bulbs, European legislation has already banned the manufacture and import of 100-watt incandescent bulbs. In 2011, 60-watt bulbs will go, and 40- and 25-watt bulbs will be banned by 2012.
But are eco bulbs that good?
The amount of light the menufacturers say they give off is misleading, most claim that a 10-12 watt cfl bulb is equivalent to a 60 watt normal bulb, untrue, they only have to claim the nearest equivalent of a incandescent bulbs with a soft white light, but most people use clear bulbs which are brighter. The EC recommends deviding the normal wattage by 4, so a 60watt normal bulb would be replaced by a 15watt cfl. The US say devide by 3, so a 60 watt bulb becomes a 20 watt cfl.
Also a cfl wattage is calculated at 20 degrees C but can be lower by as much as 10-20% when the cfl is warmer or colder than 20deg C, the cfl can get warmer by fitting in recesed fittings or shades.
Cfl bulbs also lose about 20% of their light output over time. None of this happens with a normal bulb.
Another thing is that they are supposed to last years, not accurate.
Whilst branded bulbs may last 10 years, but dont normally, supermarkets own brands and cheaper brands often have a shorter life.
When a batch of bulbs is tested, they are turned on for three hours, then off for 20 minutes over and over again until half the batch fails. This point in time is then decreed the average life.
It is often 10,000 hours. As no-one adds up the hours a light is on over its lifespan, this is translated as 10 years, on the assumption that the bulb will be on for an average of three hours a day.
But as half the bulbs will fail before 10,000 hours, a shopper may be unlucky enough to pick a dud that will fail after just 2,000 hours. However, the main manufacturers do their best to make bulbs that cluster around the average life mark, says the Lighting Industry Federation.
And what you do with a bulb can affect its lifespan. Continuously turning it off and on every 15 minutes, for example, will more than halve its expected lifespan.
Do they save energy, not as much as you think.
The European Commission, the Energy Savings Trust and manufacturers say CFLs use up to 80% less electricity than traditional bulbs. But it's an "up to" 80% claim. The EC says the saving can be as low as 60%.
When you see an 80% savings figure on the side of a low-energy light bulb, it doesn't actually mean that you're going to save 80% lighting energy, 80% carbon emissions, and 80% costs.
Traditional bulbs expend about 95% of their energy producing heat.
Let's say your house uses 1,000kWh a year to produce the light you use. If you were to replace all the old-fashioned light bulbs with the modern low energy lamps, you might expect an 80% reduction - 800kWh. However you'd find about 60% of that 800kWh would get automatically chucked back in by your thermostat-controlled heating system. A typical heating system is only about 75% efficient. So the actual figure you end up with is more like 240kWh a year saving, rather than the 800kWh saving you expected.
Also they contain murcury, so you cant throw them in your bin when they do blow.
Source BBC
BBC News - Why eco-light bulbs aren't what they seem
But are eco bulbs that good?
The amount of light the menufacturers say they give off is misleading, most claim that a 10-12 watt cfl bulb is equivalent to a 60 watt normal bulb, untrue, they only have to claim the nearest equivalent of a incandescent bulbs with a soft white light, but most people use clear bulbs which are brighter. The EC recommends deviding the normal wattage by 4, so a 60watt normal bulb would be replaced by a 15watt cfl. The US say devide by 3, so a 60 watt bulb becomes a 20 watt cfl.
Also a cfl wattage is calculated at 20 degrees C but can be lower by as much as 10-20% when the cfl is warmer or colder than 20deg C, the cfl can get warmer by fitting in recesed fittings or shades.
Cfl bulbs also lose about 20% of their light output over time. None of this happens with a normal bulb.
Another thing is that they are supposed to last years, not accurate.
Whilst branded bulbs may last 10 years, but dont normally, supermarkets own brands and cheaper brands often have a shorter life.
When a batch of bulbs is tested, they are turned on for three hours, then off for 20 minutes over and over again until half the batch fails. This point in time is then decreed the average life.
It is often 10,000 hours. As no-one adds up the hours a light is on over its lifespan, this is translated as 10 years, on the assumption that the bulb will be on for an average of three hours a day.
But as half the bulbs will fail before 10,000 hours, a shopper may be unlucky enough to pick a dud that will fail after just 2,000 hours. However, the main manufacturers do their best to make bulbs that cluster around the average life mark, says the Lighting Industry Federation.
And what you do with a bulb can affect its lifespan. Continuously turning it off and on every 15 minutes, for example, will more than halve its expected lifespan.
Do they save energy, not as much as you think.
The European Commission, the Energy Savings Trust and manufacturers say CFLs use up to 80% less electricity than traditional bulbs. But it's an "up to" 80% claim. The EC says the saving can be as low as 60%.
When you see an 80% savings figure on the side of a low-energy light bulb, it doesn't actually mean that you're going to save 80% lighting energy, 80% carbon emissions, and 80% costs.
Traditional bulbs expend about 95% of their energy producing heat.
Let's say your house uses 1,000kWh a year to produce the light you use. If you were to replace all the old-fashioned light bulbs with the modern low energy lamps, you might expect an 80% reduction - 800kWh. However you'd find about 60% of that 800kWh would get automatically chucked back in by your thermostat-controlled heating system. A typical heating system is only about 75% efficient. So the actual figure you end up with is more like 240kWh a year saving, rather than the 800kWh saving you expected.
Also they contain murcury, so you cant throw them in your bin when they do blow.
Source BBC
BBC News - Why eco-light bulbs aren't what they seem
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