Converting an A/C to a heat pump is a bit like upgrading an old Lenovo laptop to a modern CPU. It’s surely doable, and the parts are unlikely to be terribly exp

Converting an A/C to a heat pump is a bit like upgrading an old Lenovo laptop to a modern CPU. It’s surely doable, and the parts are unlikely to be terribly expensive, but as a practical matter it’s pretty specialized and no one does it. What you do is wait for the A/C to hit end of life (or end of efficient life if new systems are enough more efficient) and replace it outright. (I once got a quote, in an expensive market, to add an A/C to an existing furnace and, separately, to remove the furnace and add a three-head multi-split heat pump. The two quotes were almost the same price. The equipment is not especially expensive.)