HVAC units and insulation contractors

We jsut bought in the area and though we keep the unit at 62, last month our bill was $800 and this month it will look like it will be 1k. HVAC company checked it and said it worked fine but the cost is 😱 we are trying to find someone who can maybe spray in additional insulation to help but I’m wondering if maybe a different unit would be more efficient than what we have. At this rate, a 7k new unit would pay itself off after 7 months of these super high prices. The house is only 1700 sq feet. I would point out even at 62, auxiliary is always kicking on to maintain the temp. We are at the top of the mountain. I’m suspecting that the unit is too small. Any leads or suggestions for perhaps a more efficient unit or remediation and:or contractors to install insulation, I would be grateful.