This is example highlights the benefits of heat pumps as the heat from the gas furnace is waste heat from something functioning on an entirely separate purpose that will occur independently from the water heater. In turn this situation benefits the heat pump as it is actually more efficient to scavenge the wasted heat from the gas furnace. It is super odd that your post is suggesting that it is not efficient because it is using “extra electricity” when the efficiency is from reduced running costs(money) and not hype fixating on just electrical usage. On the flipside, a gas water heater will use extra gas to heat the water, too! This is just silly