I have used Ethan from Sustainability Now in a number of strata complexes, and in each we were have been able to make substantial improvements to our energy use and costs based upon the advice / report given.
The Green Strata website that Lady Penelope mentioned is a treasure trove of great information on this subject. Coincidently Ethan has been involved in that over the years: https://greenstrata.com.au/acknowldegements