How Do Real Estate Professionals Judge the Relative Energy Efficiency

How do real estate professionals judge the relative energy efficiency of a house?

A) by making an honest, good faith estimate based on their experience
B) by looking at the house blueprints filed at the registrar
C) by using complex instrumentation that measures heat loss in different parts of the house
D) by setting up sonic emitters at the windows and listening with a special detector outside
E) by asking for utility bills for the last 12 months and comparing it to other houses