I have a two story 1800 sq foot home and I need to replace the central heat and air unit. Is a 14 or a 15 seer standard for this size of home? Or would the 15 seer be a waste of money?

The higher the SEER the more it costs BUT a higher SEER will save you money on the utility bill. There is NO set standard for home size but there is a set minimum standard for energy efficiency which is 13 SEER.