Selecting Low-Consumption AC
To choose a high-rated air-conditioner, look for qualified models with a high EER/SEER (energy coefficient).
Take into account the UE eco-labeling, in European countries, or the Energy Star rating in USA, Canada, New Zealand and Australia. Do not choose a central AC with a low SEER. Look for a central AC with a SEER rating above 15, or a room unit with a EER above 12.
AC Technical Information
Toolbase organization has a wealth of information about HAVC equipment. See: Toolbase and HAVC.
To see if there is any state incentives for high-efficient air conditioners, take a look at:
In Canada, see: Office of Energy Efficiency Grants and Incentives
In USA, see: Energy Star and tax credits information.
Data on federal incentives in USA, see DSIRE USA
Local tax incentives, see DSIRE
See Energy Rating Australia Government
See Energy Saving Trust
Air conditioner sizing tools
Using charts and calculators only makes sense for portables and room air conditioners. Consider, in such case, a chart like the Energy Star one here.
The main AC manufacturers can help you find their dealers, contractors and qualified technicians. Just call them, or take a look at their sites.
North-America: ACEE (North America) and Natex (American Technician Excellence) and ACCA (Air Conditioning Contractors of America) or even Resnet (USA).
Europe: European HAVC Associations.
Australia: Energy Rating Australia Government