Whether or not a forced air gas furnace is less expensive than an electric heat pump depends on the type of each that you have. There are a lot of gas furnaces that burn only at around 78 percent, which is not really that efficient. This means that for each dollar you spend on gas, only 78 cents is used up to generate the heat. The rest goes out the chimney. However, the government has mandated to have these heaters generate heat at 78 percent efficiency at least. Depending on the price of these heaters, it may be wiser to just get the electric heat pumps since these have thermostats that automatically shut off the heating process when the room reaches the desired temperature.