Because you are buying now two appliances, a water heater and air conditioner, “heat pump heaters are twice as expensive” as the old electric water heater
EPA Regulations forcing compliance on new appliances
If you ask an engineer, he will tell you that CO2 is not a pollutant, and burning fossil fuels has made the Earth greener because their emissions are rapidly assimilated by sunlight. As Dr. Klaus Kaiser had explained, “incomplete combustion can cause air quality problems, not because of CO2 but due to soot particles and nitrogen oxides,” particularly in high density urban areas where the air tends to be stagnant. There is a reason why Chicago, the ‘Windy City,’ has not had an air quality problem.
The green biomass, including trees and plants, is 99 percent carbon and water. This carbon comes from atmospheric CO2, including CO2 dissolved in rain water or taken up by the oceans. “Higher atmospheric CO2 dramatically accelerates growth of green biomass above a minimum concentration of 200 parts per million (0.02%). Below that concentration (about 50 percent of CO2 level in the air today), it’s difficult for plants to keep growing.”