A measure of cooling capacity: one ton = 12,000 BTU/h, historically the melting power of a ton of ice per day. Home systems typically run 1.5–5 tons — and the right number comes from a load calculation, not square footage alone.
Around Baltimore, Annapolis, and the DC metro, cooling decisions revolve around humid Mid-Atlantic summers, correct sizing for row houses and older homes, SEER2 efficiency, and whether a repair or a planned replacement is the smarter long-term spend.