People often confuse economic and economical.
Use economical to describe methods, products, machines etc that are not expensive or do not waste money or other resources:
✗ They want people to buy more economic cars.
✓ They want people to buy more economical cars.
✗ Email is an efficient and economic way of contacting a large number of people.
✓ Email is an efficient and economical way of contacting a large number of people.
Use economic to describe things that are related to the economy of a country and how well it is performing:
✗ a long period of economical growth
✓ a long period of economic growth
✗ a serious economical crisis
✓ a serious economic crisis