Will Replacing a toilet really save that much water?

I was thinking about replaing an old toilet to save water, any suggestions on which one I should buy for this purpose and costs?

Yes, it will save water. How many people in the house and how much of the day are there there verses say at school, the office, or elsewhere? How much does the current toilet use? The really old ones could use as much as 8 gallons/flush. The newest dual-mode flush ones use like 0.8gallons/1.2gallons, depending on the mode. So, depending on how many people and how long they are home, many hundreds to thousands of gallons per year. In many places, that affects not only the cost of water, but also the sewage charges as well.

Look at the Toto Drake II as a starting point. Some of the choices are style, height, single-piece, two-piece, skirted, 'traditional', elongated, round. Toto is the largest toilet manufactuer in the world, and has a huge variety of toilets from several hundred dollars, to many thousands, depending on style and options.

Say the old one is a 5g model, new one is 1.2
Per person savings, multiply by the number of people
Min I'd say 3 flushes a day....old toilet 15g vs 3.6g new toilet
11.4g per day....average 30 days a month = 342g of water a month......4,104g of water a year

Even more importantly (I've found after purchasing 3 new toilets, while taking advantage of a local rebate) is answering the questions of friends, family, neighbors and coworkers who express interest -- especially if you've done your homework beforehand. I've referred a few people to this site and others that have toilet info, and let them know how easy the process is (assuming no floor repairs are necessary and water supply pressure is adequate). For every person you steer to a new low flush toilet, that's another 4,000 gallons of water saved that you can take as "feel good" credit.

using scuba dave's numer of about 342 gallons per month, at the rate we pay for water in San Diego, that would amount to about $4 per month. That won't pay off the mortgage , but it all adds up. If you factor in that amount over a couple of years, plus a rebate if your area does that, it does pencil out to get a good toilet.

Yes, they will save that much water, but spend some time getting an education about toilets from this forum. You will learn that all toilets are not created equal and some of the famous name brands have not redesigned their toilets to perform. Toto leads the pack in this regard. Some of the old names are still using designs that may have worked fine with 7 gallons of water or even 3.5 gallons of water, but just don't do the job with 1.6 gallons or the newer 1.28 gallons per flush models.

I am not "brand specific" and use many different toilets, Toto being one I seldom use, without any customer complaints. But I also doubt many "friends and relatives" are going to notice your new toilet and start a discussion about it, unless you start the conversation.

Frankly, I have been surprised how often the topic comes up without me initiating. Many know I'm doing work on the house and have outright asked my opinion, but many others have mentioned "by the way" they were thinking about replacing a toilet for whatever reason -- not my prompting. Ordinarily I might have responded "oh that's nice" but now I can give them some pointers / advice / encouragement and a nudge in the right direction.