How much energy do I waste if I don't switch off my computer at night?

That depends on your setup. Flat screen monitors and notebooks consume less than a PC with a conventional CRT monitor. It also depends on whether your computer is Energy Star rated and whether it enters standby (powersave) mode.

We use the rule of thumb that a PC with monitor consumes:

• 116 watts/hr when ON
• 35 watts/hr when in STANDBY
• 6 watts/hr when OFF

If left ON for 14 hours each night and throughout the weekend, a PC and monitor will waste €64 per annum and result in the unnecessary emission of half a tonne of CO₂. In STANDBY, it will waste €19 per annum and 170 kg of CO₂. Each of the colleges has thousands of computers, resulting in a very high overall cost.

How does energy use cause global warming?

The combustion of fossil fuels such as oil and natural gas produces carbon dioxide (CO₂). In Ireland most electricity is generated from the combustion of fossil fuels. When we consume electricity or heat, our actions indirectly produce CO₂.

Greenhouse gases, of which CO₂ is the main one, trap the heat of the sun in the earth's atmosphere, resulting in overall warming and climate change. The amount of CO₂ released into the atmosphere due to fossil fuel use has increased tenfold in the last century. Energy use is responsible for two-thirds of Ireland's greenhouse gas emissions.

Likely effects of climate change include changes in weather patterns, increases in flooding, droughts and storms. Some scientists see a risk of a colder climate for Ireland if the Gulf Stream is diverted. (Source: SEI)

I was told to leave fluorescent tube lamps on because switching them uses more energy than running them — is this true?

In the past, when electro-magnetic ballasts were used, there may have been some sense in this argument. Nowadays fluorescent tubes have electronic ballasts and their switching uses very little energy. In general, it is better to switch off when not required.

How much do vending machines consume?

A recent study of several vending machines in UCD found that they consume 7,000 kWh, cost €630, and result in the emission of 5.5 tonnes of CO₂ each year.

Which is better for heating: electric heaters or gas-fired central heating?

In almost all circumstances, gas-fired central heating is better. Consuming a unit of electricity costs approximately 9 cents and produces 0.78 kg of CO₂. Consuming a unit of gas costs approximately 3 cents and produces 0.2 kg of CO₂.

Are electric heaters expensive to run?

Absolutely. A typical 2 kW heater running on full power costs 18 cents per hour and produces 1.6 kg of CO₂. These heaters are often run unnecessarily and left on.

What does the unicorn in your logo represent?

The unicorn in the e3 logo represents purity, energy and it symbolizes the balance of the yin and yang and the power of nature. The word 'unicorn' comes from the Latin 'Uni', meaning one.