HVAC
Heat pump versus gas furnace, SEER-upgrade payback, and the repair-cost threshold where replacing a working system finally becomes the stronger move.
Most HVAC decisions here share the same shape: a system is failing, aging, or up for an efficiency-tier upsell, and the real question is whether replacing it now beats repairing it or waiting. Every engine uses your own quoted costs and ownership horizon, never a regional average, since the same furnace replacement pays back on a different timeline in a cold climate than a mild one. Start with a replace-vs-repair tool if a system just failed, or an efficiency-upgrade tool if you are comparing tiers on a working one.
For the ideas shared across every HVAC engine, see Repair-or-Replace as an Economic Decision.