Modern systems are much more efficient, so when replacing the HVAC system, simply getting a new system of the same size may not be ideal.
Heat Load Calculation, Cooling Load Calculation
A system that is too large will cost more to run and not deliver any benefit for that extra cost. A system that is too small will become overworked and wear out faster.
Costs vary greatly by region (and even by zip code). To get free estimates from local contractors, please indicate yours.