If we want to save energy, then we should use energy economically.
This statement can be written in the form of a logical statement using the conditional "if...then" structure. The "if" part of the statement is the condition that we want to achieve, which is "to save energy." The "then" part of the statement is the action that we should take in order to achieve that condition, which is "to use energy economically."
The statement is logical because it establishes a clear relationship between the condition and the action that will lead to the desired outcome. In this case, if we use energy economically, we will be able to save energy. Therefore, the statement is a valid and reasonable assertion about how to achieve the goal of saving energy.