If Energy cannot be created nor can be destroyed then why should we conserve energy?
Answers
The law is -
"Energy can neither be created nor destroyed but only transformed from one form to another"
Energy forms can be Mechanical, Electrical, Chemical, Magnetic, etc.
Resources means the materials that can be used to extract the required kind of energies. So, to drive your vehicle, you use the resource called fossil fuel and CONVERT its Chemical energy into Mechanical energy which is used to move the vehicle. That mechanical energy is then used to drive an alternator to generate electricity (i.e., mechanical energy is further converted into electrical energy) which is used for lighting, heating which are again in their own right conversion of electric energy into electromagnetic radiation(Light) and Thermal Energy (Air Conditioning)
So, Energy is just being converted, but the fuel is burnt. It is gone and there is no more chemical energy left to convert into Mechanical, electrical, thermal, etc. To get back that spent energy into chemical form again, it will require millions of years of high pressure compression of biomass under the earth (which was how the fossil fuels were made in the first place)
Another example is using the potential energy of water stored at a height and running it down a slope and then use it to generate electric energy. Once the water comes down, that resource of water with potential energy is not spent. Unless there is rains and more water accumulates at the height, there is no chance of producing more electricity. Hence, we need to conserve that resource and use it in a sustainable manner.
I hope you get the difference here and why the resources need to be conserved.