Get a solid SEER rating, but always understand how they work and their efficiency due to outside temperature. The heat pumps work excellent right up until it drops below 40. They are still usable but draw more electricity until about 5 degrees where most give up. Also understand the BTU ratings. If it takes a 100k BTU heating system to heat your house you will still need 100k BTU's to heat your house so a 30k unit will not get the job done especially seeing most only give 80% when used for heat.