I’ve had it for years. Every 6 month they re-evaluate your use. So you see your actual amount each month (that you actually use) and then there is the agreed amount. The way I think it works is they take the total of the 6 months and average it. Then do that the next six months. During the winter my bill is more because im paying the summer estimate. In about may? My bill gets much cheaper through December because it’s based on winter usage (no ac) you can cancel it anytime but you have to pay that “ actual” balance you used. Right now with everything being so expensive it’s nice to know exactly what you’ll be paying.