Tell me about your energy bills, the size of your house, the number of its occupants, and your climate; and tell me about your windows and their size and if they face the sun or not, and the age of your appliances, and the type of your heating and cooling system, and the insulation levels of your attic, walls and floors, and some of your habits involving baths, and cooling and heating… and I will tell you the home energy improvements that you should undertake, and the savings that you will get with the energy improvements….
That’s basically the idea behind the best energy auditing software. They will require the data that we have mentioned (or some of it), and they will recommend energy improvements and show the benefits that you will get.
Helpful or useless?
Some of these online tools are helpful. But be aware: do not expect too much from them, even from the best. They don't replace a professional energy audit or your own assessments and commitment.
Most of these tools are useless, and data errors and omissions can make their recommendations ambiguous, at best.
The best online tool (to our knowledge) is the Lawrence Berkeley National Laboratory’s Home Energy Saver. It's American software, expressly designed for American homeowners, requiring you to enter a Zip code - to identify your climate zone and to take into account climate considerations.
Using them outside the USA
But… you can use it outside the USA, as long as your climate matches one of the several American climate zones (see US Climate Zones). You just have to choose an American city and the zip code that matches your climate.
The Lawrence Berkeley National Laboratory’s Home Energy Saver and the Energy Star energy auditing software for Energy Improvements
The Lawrence Berkeley National Laboratory’s Home Energy Saver is able to estimate the levels of savings for several recommended upgrades.
This program is sophisticated and requires a large set of data. You can access it here: Energy Audit Saver.
The Energy Star Home Energy Yardstick is a lot simpler. It will require your Zip code, the home's square footage, the number of occupants, the fuel you use with your appliances and heating equipment, the last 12 months of utility bills, and not much more.
This program will give you some tips and insights on what to do to improve your heating and cooling equipment, or your appliances and hot water system and lighting, but not much more; it mostly provides links to pages where you can look for information on home energy improvements, and an estimation of your home's carbon emissions.