There are many kinds of power plants so some produce more energy than others.
Nuclear power plants produce energy from controlled nuclear reactions. They use nuclear fission, not nuclear fusion. Right now many people believe that nuclear fusion is a better and safer way to produce energy in a nuclear power plant but they have not yet really discovered a way to make it feasible in this setting.
Hydroelectric dams produce a lot of energy as well. They use the power generated from flowing water to create electricity. An example of this is Hoover Dam which generates electricity to a vast area including Arizona, Nevada, and southern California.
Wind turbines also create a lot of electricity. There are many wind power plants being constructed as is it a safer and more environmentally friendly. The problem with this is they take up a lot of space and do not create nearly as much electricity as other types of power plants.
There are also power plants that use fossil fuels as a source for energy. These kinds of plants burn oil and they are expensive and very polluting. As fossil fuels are running low, different kinds of power plants are thought to be a better option.
Power plants generate electricity by spinning coils of wires inside of magnets (or they can spin the magnets inside of coils, it doesn't matter). Power plants can generate lots of electricity because they can spin really large magnets or really large coils of wire. This makes lots of electric current.
The problem is that you need some sort of energy to make the magnets or the coils spin. Most of the time, that energy comes from steam. The steam is made by using some sort of fuel (often coal or oil).
It is important to conserve energy so that not so much coal or oil is used to make the steam that spins the coils or magnets.
Power plants generate try to generate as much electricity as is required by the consumers to whom the electricity is supplied. It will not be the right approach to conserve energy by simply reducing the electricity supplied by the power plants. This approach to conservation of energy is most likely to effect adversely both industrial production and comfort and well being of consumers in general.
We try to conserve energy because of two reasons. First is because many of the world has limited quantity raw material or fuels such as petroleum and coal used for generating power, and unless we take care to conserve these resources, we will soon run out of them. Second reason for energy conservation is the pollution that is caused during the process for generating power from burning fuel.
The best approach to energy conservation involves more efficient use of energy so that less power is required for the same level of industrial and other economic activities. To some extent, energy conservation can also include changing our lifestyles to reduce the total power requirement. This includes action like managing with slightly lower temperatures an homes in winters to reduce energy used for heating, and pooling of cars for commuting. However, such programs should be gradual and directed at reducing demand rather than on arbitrarily cutting down electricity generation.