Low flow toilets averaging around 1.6 gallons per minute are a great idea. But the return on investment period is long considering you’ll have to shell out at least $300 between the cost of the toilet and replacement labor costs (plumbers are not cheap). The toilet tank bank and Niagara dual flush tank are cost-effective alternatives.
Another option is to do a retrofit on your toilet e.g. fill valve so less water gets released, and at less then $20 these deliver a very quick ROI. My favorite is the toilet tank bank – which is the poor man’s solution. At around $1.25 these are a no brainer. Simply fill them with water and stick them in your toilet tank. Instant low flow toilet!
The N7714T-DF Niagara dual flush tank is an Ultra High Efficiency tank that uses either 0.95 or 0.5 gallons of 
water per flush. The Stealth technology has truly changed the market in that it features a low-profile body, ultra quiet flush, and patented hydraulic technology. An elongated toilet bowl is sold separately, and can adapt to fit a 12″ rough installation. The Stealth line of Ultra Efficiency Toilets easily replace existing toilets. By providing 2 flush options, they reduce water consumption and costs like no other models out there!
Most of the time you’ll only be needing 0.8 gallons per flush so why not stop that extra 0.8 gallons from going down the toilet!