External shading systems
In some situations, it is best to use a shading system on the exterior of your home, rather than inside. Exterior shades block out the light and heat before they enter your home, so that you are one step ahead of the heat that increases your electric bill.
A central air conditioning unit can use as much as 3500 watts per hour, literally blowing away all other electricity users in your home. Since direct sunlight increases your home’s temperature by as much as ten to twenty degrees, it seems obvious that stopping that sunlight will decrease your need to run the air conditioner. The key is finding the perfect balance between solar screening and room darkening. Do not completely block out all natural light, or you may end up using more electric light, which can generate heat as well. However, solar screens are capable of blocking out sun-generated heat – as much as 60-70% – while still allowing ample light in the room.
External shading systems, such as retractable awnings, can not only beautify your home, but also create functional spaces from areas that were too hot to enjoy. Awnings can provide shade during sunny days and protection from the rain. Plus, since they are retractable, you can remove them for overcast days or those warm spring days when the sun is peeking from the clouds for the first time since last autumn.
Motorized controls for retractable awnings can be used manually, set to a timer, or linked to environmental conditions, such as amount of sun, wind, rain, or other factors. This is beneficial for individuals hoping to reduce glare, UV rays, and heat in the interior rooms of their home.
Reducing your electric bill is as easy as adding an eternal shading system.
Resource: http://michaelbluejay.com/electricity/cooling.html