Is there an idiom about wasting money and a window?

Solution 1:

The most commonly-used equivalent English phrase is:

Pouring/throwing money down the drain

Fig. to waste money; to throw money away. "What a waste! Buying that old car is just pouring money down the drain. Don't buy any more of that low-quality merchandise. That's just throwing money down the drain."

Solution 2:

I have often heard other American English speakers say, "that's just like throwing [or tossing] money out the window" when referring to someone wasting time or resources (eg - not closing a door in winter), or buying unnecessary items or services. I don't remember the last time I heard this phrase said, but don't believe that this english idiom has gone out of use. I am 55, and idioms - like slang - do go out of favor over time and/or enter regular use after people hear the popular actors or celebrities of the day say them on TV or in the movies, hear popular singers use them in song lyrics, or see or hear them used in current books, media or advertisements.

Solution 3:

A slightly more "colourful" version is to flush your money down the toilet.

See http://www.google.com.au/search?q=flushing+money+down+the+toilet