The answer to 'why is my mini split high energy bills' is that there are several common causes, including improper sizing, poor insulation, air leaks, and inefficient compressor operation. Mini split systems that are not the right size for the space, have inadequate insulation around the indoor and outdoor units, or have air leaks around the refrigerant lines and indoor air handler can all contribute to high energy usage and bills.
Another potential cause is an inefficient compressor or other internal components that are not functioning optimally. Over time, mini split systems can lose efficiency and require maintenance or repairs to restore performance and lower energy costs.