Bigger HVAC equipment is not necessarily better. In fact, an over sized system will cycle on and off often, which results in a less comfortable home and higher energy bills. This often causes uneven temperatures in the home and, because the system turns off more quickly than it should. On a hot summer day, feeling cool but damp in your home is not pleasant.
Insist that your contractor perform a Manual J calculation. This is the best method for him to most properly decide what is the best size of equipment necessary for your home. Among other things, The Manual J calculation takes into account such details as how many windows your home has and what direction they face. A Manual J type calculation is a requirement for any “Quality Installation Certification”