Yes it is illegal for them to be using your electricity!
What I would do is tell them that need to find a different way for the electric and the trash.
Only offer to buy them groceries. That way you know how the money is spent, plus your still helping your fellow neighbor.
Ask your husband to read this page
Leviticus 25:17 Do not take advantage of each other, but fear your God. I am the LORD your God.
Hope this helps.
Blessings