Whether you need both a furnace and a heat pump depends on your climate and heating and cooling requirements. In moderate climates, a heat pump alone can efficiently provide both heating and cooling throughout the year, making it a cost-effective and energy-efficient choice. However, in colder climates where temperatures regularly drop below freezing, a heat pump may struggle to extract sufficient heat from the outdoor air during winter, and supplemental heating from a furnace or electric resistance heating may be necessary for efficient heating. This setup, called a "dual-fuel" or "hybrid" system, combines the efficiency of a heat pump with the added heating capacity of a furnace when needed, providing versatility and cost savings in regions with extreme temperature fluctuations. Consulting with an HVAC professional can help you determine the best heating and cooling solution for your specific climate and needs.