Some common signs that you might need a new furnace rather than a repair include:

1. Age of the furnace: Most furnaces last between 15 to 20 years. If yours is in this age range, it might be more cost-effective to replace rather than repair.
2. Frequent repairs: If your furnace needs frequent repairs, it might be nearing the end of its life.
3. Rising energy bills: If your energy bills are increasing without a clear reason, it might be because your furnace is losing efficiency.
4. Inconsistent heating: If some rooms are colder than others, or the furnace can’t maintain a consistent temperature, it might be time for a replacement.
5. Unusual noises: Loud or strange noises coming from the furnace can be a sign that it’s time for a new system.
6. Poor indoor air quality: An old furnace might not filter the air as well, leading to dust, dander, or a stale smell in the house.

It’s best to consult with a professional HVAC contractor who can assess the condition of your current system and make a recommendation based on your specific circumstances.