It's no secret that many of the people reading this are doing a lot of green stuff for two main reasons: 1) To reduce their burden on the Earth's ecosystems, and 2) to save some dough. That's perfectly fine, nothing to be ashamed about, especially in these tough economic times.

But some people are hard to convince. "Why should I turn turn down my air conditioner and drink tap water," they say. "After all, I'm making $50,000 a year, so those savings are insignificant."

Well, is that true? Say that you could save a few hundreds of dollars by cutting down on your energy use, by consuming less, and following some of the other tips on Planet Green and our sister site TreeHugger. How big a difference would it make to your budget?

The real answer can be found by looking not at your gross income, but rather at your disposable income.

That's a very important point, and needs to be repeated: Disposable income is what matters.

If you make $50,000 a year (random number) but $47,000 of those dollars are going to: pay taxes, pay the rent/mortgage, car payments, utility bills, groceries, education, putting money aside for retirement, etc... Not much disposable income is left (it's a whole other discussion, but I hate the term "disposable income"

So those few hundred dollars of savings are actually quite big compared to the $3000 (for example) you have left at the end of the year. That's what frugal green living is about, making a noticeable difference, both for you and the planet, and our world definitely needs a good dose of green personal finance education the way people are spending their ways into financial and ecological holes.

Read more about going green and saving money in our eco-nomics feature.

Got a tip or a post idea for us to write about on Planet Green? Email pgtips (at) treehugger (dot) com.