[brummm]

Like the other commenter hinted on, it depends on the ambient temperature. While for certain temperate ranges (above 0C) heat pumps are in their high efficiency range and depending on local electricity prices might be cheaper, it can change quickly once temepratures go below freezing. So there is a break even point where heating with gas is cheaper below that temperature and above heating with electricity through the heat pump is cheaper. Where that temperature is, depends on gas and electricity prices as well as your heat pump