High utility bill due to hvac unit
We live in KY and are in the final stages of adding on to our house. We added a new hvac unit to the new addition but kept the older one (4years old) but reran some registers to heat and cool the existing house. We turned on both units about 6-8 weeks ago and our December electric bill was 220.00 and we do not live there, we have no appliances, and no hot water heater hooked up. The electric company told us that next month we are looking at 600.00 because we are using so many kw. We think the problem obviously has to do with the heat and air units. Any suggestions or where do we start?