We are building a new house 2 story its 2300sf with 500 extra sf in basement.The builder is installing a 3 ton 13 seer heat pump. I have looked around on the web and been to a few web sites that tell you to enter sf and zip all say around 4.5 or 5 ton.My zip is 45005 Ohio house has 15 windows 6 in front 7 in back 2 on the sides house faces north has 11in 30r in attic not sure on what walls are .Is a 3 ton enuff it's a tempstar unit thanks for reading

Share this info with your installer. See if he can give you a reason for going with the size he recommended. Internet can be a wicked tool. Your installer has seen your house and probably has a better idea of what you need. If the installer has been in business for any amount of time, he has most likely installed many systems such as yours. I would trust him(if he is reputable) above online advice.