Get the complete demand
Request the outdoor-unit, indoor-unit, and backup-heat models, running demand, startup requirements, voltage, and manufacturer limitations for generator use.
Running power and starting power are different. Generac's sizing worksheet distinguishes continuous demand from the extra power needed to start motor-driven equipment. A worksheet is a starting aid, not approval for your installation. Generac generator-sizing guidance.
Do not judge suitability from the efficiency label, cooling size, or breaker rating alone. The indoor blower, controls, backup heat, and accessories need to be included.
Check the actual arrangement
Give the electrician the generator and transfer-switch models, fuel used, backed-up circuits, and other expected loads. Refrigeration, pumps, medical equipment, and cooking may compete for capacity.
Ask whether all necessary heating circuits are backed up, whether transfer equipment and protection are suitable, and whether approved load management is needed. Get an explanation of what can run together and how backup heat will be handled.
Do not move circuits, alter transfer controls, bypass protection, or add a startup device yourself. Proposed accessories must suit the exact heat pump and be coordinated with the electrical provider.
Define what it will provide
Request a written plan identifying supported modes, operating limits, and an authorized test. A successful compressor start does not establish sustained heating under every condition.
Use a portable generator outdoors only, at least 20 feet from the home, with exhaust directed away from nearby buildings. Never operate it in a garage or other enclosed space. CPSC generator guidance. A transfer switch does not make an unsafe generator location acceptable.
Your next step is to make backup compatibility a written part of the proposal review. If the arrangement cannot provide adequate heat, plan another heated place for outages rather than rely on an untested connection.