What was the weather this past couple months versus last year? If colder that could cause it.

Does your provider allow you to look and track usage by day/hour? Some do on the website. That could help identify the issue.

See https://www.reddit.com/r/personalfinance/comments/q8gadf/comment/hgpcfvr/?utm_source=share&utm_medium=web2x&context=3 who had a similar problem and some advice.