which is/are the most energy efficient?  Efficiency should be considered from two perspectives - 

(1) use of energy delivered to and used within the building boundary 

(2) use of the primary energy source (for example, coal used to power an electric generating station).  The former perspective will require you to investigate the efficiencies of current heating systems available on the market today; you are to tabulate these comparisons in your report.  The latter perspective will require you to investigate energy losses from a power plant to the point of use. 

• Explain the differences in the energy efficiencies and their consequences relative to emissions, energy use, and cost to operate these systems.
• Describe recent innovations that improve the efficiency of these systems and discuss any on-going R&D activities aimed at further improvement of the efficiencies of these systems.