Intended Consequences: These are the outcomes that are not only desirable but sought after in developing an energy policy. If we're looking at a policy to implement higher fuel economy standards on passenger vehicles to reduce gasoline consumption and greenhouse gas emissions, and the policy effectively forces automakers to comply with these new standards, that's an intended policy consequence.
Unintended Consequences: When policy makers (energy policy or otherwise) are crafting policy design to handle specific issues, they need to pay careful attention not just to the consequences they're intending to achieve with the policy, but also the ones that might come along as byproducts of the policy design. When we talk about unintended consequences, we're usually referring to a negative, unforeseen consequence of a seemingly well-intentioned policy design. For example, one of the most prominent cases of unintended consequences in a policy related to energy is the case of ethanol. Policies enacted to stimulate corn ethanol production in the United States in an effort to reduce greenhouse gas emissions and dependency on foreign oil have come under harsh criticisms for a host of potential unintended consequences such as food scarcity, increased greenhouse gas emissions, increased food prices, water and air pollution, and ecosystem disruption.
There are however, some times when the unintended consequences of energy policy are beneficial. One example of this can be found in the case of policies instituted to reduce carbon monoxide emissions from car exhaust. Reductions in carbon monoxide emissions in car exhaust appear to have led to a decrease in carbon monoxide poisoning suicides. (Curious? Read Unsuccessful Suicide by Carbon Monoxide: A Secondary Benefit of Emissions Control and Suicidal Asphyxiation by Inhalation of Automobile Emission without Carbon Monoxide Poisoning to learn more.