We can save the energy by consuming less energy. That is the only way to do it. It is that simple. The more we consume, the more we will have to produce from fossil fuels or nuclear plants, which is not sustainable. If we reduce our consumption, then we can replace that amount of fossil fuel/nuclear power with clean renewable energy and still be able to meet our needs. Not only that, but we will be far better off since most of the energy consumed goes towards things which are not really needed or cause harm to health and environment (e.g., pointless transportation, junk food which causes obesity).
To reduce our consumption of energy, we need to change our behavior at an individual level and also at a societal level by changing policies and regulations.
At an individual level:
* Stop using cars for short trips (or any trips if possible). A bike or even walking is better for your health and the environment.
* Stop using air conditioning (AC) in summer and central heating in winter. Wear appropriate clothing depending on the weather instead of relying on artificial climate control systems; live in a house which is well insulated so you don't need AC/heating as much; plant trees around your house for shade during summer. Another idea is to use a solar panel if you have one in your house. This is a great way to save energy because you are not being charged for the electricity being used by your solar panel. If you do not have a solar panel at home, I would suggest that you get one. This will be very useful for you when saving energy in the long run. 

If everyone would do these things, we would save a lot of money and help the enviorment.