Over the last couple of years, there have been some new and very efficient Dual Flush Toilets. Upgrading your old and less efficient unit with a low flow toilet with or without a rebate will save you noticeable money over time. About the rebate, some local water jurisdictions offer rebates to their customers when they upgrade to a more efficient toilet that save water.
Check with your local water company to see if you would qualify for a rebate. By visiting a website called dualflushkit.com you can get more helpful information on these water and money plumbing products. So, upgrade your toilets and you will see your water bill go down on your very next bill.