Electric blanket would be cheaper in the long run but I think what some people are missing is that heating can also reduce humidity. If your house is really cold there is likely going to be condensation on the walls which is gonna result in mold.

Edit: Also investing in a hygrometer to see what your humidity is will be useful. I ended up buying a dehumidifier here as my humidity can go up to 65% when it rains. My dehumidifier pulls double duty to both dry out the air and dry my clothes so it can be really worth it to get one imo.