I have a townhouse with a 20-year-old 2-ton heat pump I'm getting estimates to have replaced. The main issue I'm looking to address is the noticeable temperature difference in the summer between the main floor and the warmer upstairs. So far I've mostly been told that a variable-speed blower would help this, and upgrading to a 2.5-ton unit would be less efficient.
However, I've now heard one counter argument: with a variable-speed blower, the main floor's thermostat would reach the desired temperature with a lower fan speed, and the system would shut off, with the upstairs having received less airflow and thus creating an even greater temperature difference. This contractor advised a single-speed air handler with a 2.5-ton unit to increase upstairs airflow.
So my question is, what would be best to keep temperatures even throughout the house? A variable-speed blower running either on auto or continuously, or a larger unit with a single-speed blower?