Before you decide to turn off every electronic device/ appliance in your household, consider the following.
Your local power plants constantly generates power, which are distributed through your neighborhood's transformers, and eventually end up in your home at a fraction. These power plants operates on a 24\7 schedule, and the amount of energy they create are not stored in an abundant level, except in the case of fail-safe protocols does a power plant provide minor backup electricity.
SO, by turning off all the electricity in your home, while saving bills on an economic level, does not dictate the fact that you are actually preserving energy. You are just simply not using the constant flow of electricity coming from your local provider.
Secondly, should you participate in total shutdown during Earth Hour, please consider that turning the power back on approximately after the end of the hour, may apply an incredible amount of stress on your local transformer. Reason being that there is a high chance that many people would be turning their power back on simultaneously right after Earth Hour, this causes a sudden, flooding of electrical current in the form of electric surge which can overflow the transformer. That's how your neighborhood may end up with a blown transformer, which by the way, does take days for the city to send a replacement, and at the main time, you'll have a blackout for the next couple of days.
Though the ideology that Earth Hour encompasses the awareness of utilizing and rationing electricity for the good of our environment, it would almost be counter productive and pointless to simply turn off the lights for an hour once every 365 days.
Instead, try turning off the lights after leaving a room. Install energy efficient lights/dimmer lights in your household. Open a window for a breeze, use fans instead of air conditioners from time to time during the summer.
And it doesn't have to stop there with just electricity, I'm sure there are tons of ways out there that are both environmentally friendly as well as economically efficient when it comes to energy consumption.
Don't take showers that are more than half hours long. Ride a bicycle, take public transits more often, carpool, put a mop on your baby and make them crawl to clean the floor.
Most importantly: Buy less non-recyclable and crap quality products that will only last you a couple of days/months, only to end up in a landfill for the rest of its days later on.
I hope this entry is a bit helpful in creating a more environmentally friendly community!
