Drinking water can save you $977 a year

This post comes from Paul Michael at partner blog Wise Bread.

Most of us eat out at least once a week. In fact, renowned culinary expert Zagat recently announced that although we are dining out less as a nation -- due to the poor economy -- we are still eating out an average of 3.1 times per week. That's the average. Of course, some of us are eating out daily. (See also: "A cheapskate's guide to eating out.")

And when we eat out, be it at a fast-food restaurant or something more refined, we drink soda. Oh, how we drink soda. As a nation, we can't get enough of it. Dr. Oz says that "53 million Americans drink at least one soda a day, and we spent $70 billion last year on soda."

That got me thinking. How much would we save, on average, if we substituted tap water (not bottled, please) for soda every time we ate out? Every restaurant, fast food or otherwise, has given me free water with my meal when I ask for it. And remember, I'm not talking about substituting every single soda we drink -- just the ones that accompany the meals we eat away from home.

• How much will my savings grow?

First, let's review the numbers we're dealing with.

We already know that we eat out 3.1 times per week. Now take the average family size, which, according to 2009 U.S. census data, is 3.19 people. And, as we're playing with averages, what's the median cost of a soda?

Well, the cost of soda is obviously going to change depending on where you live and where you eat. A glass of soda at a high-end restaurant in New York City is not going to be the meager $1 charged by McDonald's (although that's still a huge markup). I've paid almost $5 for a glass of Coke in a trendy gastropub. Post continues after video.

But I did some digging and found out that there is generally a recommended price for a 20-ounce soda with free refills. That price is $1.75 plus tax. So, let's round that up to $1.90.

Here's the math:

• We eat out 3.1 times per week.
• 3.19 people make up the average family.
• With 52 weeks in a year, that makes roughly 514 glasses of soda every year for an average family.
• 514 x $1.90 = $977!

What could you do with an extra $977 a year?

Right now, you could buy a really nice laptop, a whole new wardrobe, or it could go toward a vacation for your family. And all for substituting water for soda only when you eat out. It's not like you're giving it up entirely. Think it over.

More on Wise Bread and MSN Money:

• 8 natural ways to make water more flavorful
• Hungry? You should probably have a drink
• How to make your own soda
• Fast-food joints jazz up drink menus for summer
• Diet Coke outsells Pepsi for first time
• New Pepsi vending machines send friends drinks