A 1989 Sears catalog shows the price of a Kenmore AC unit.
A 1989 Sears catalog shows the price of a Kenmore AC unit. - 
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As Marketplace celebrates its 25th birthday this year, we are looking at the surprising, sometimes delightful and sometimes destructive ways that prices have changed during that quarter century.

A 1989 Sears catalog reveals that a medium capacity window air conditioner (in '80s-style faux-wood paneling) could be had for around $300. Factor in inflation, and that's about $575 in today's dollars. An equivalent 8000 BTU window AC unit, again Kenmore, today goes for just $219.

But what about the cost of running an AC unit? In the most recent period when stats are available, people on average spent $237 a year on electricity specifically for AC cooling. This includes the whole country, rich and poor, hot climates and cold. In 1989, adjusted for inflation, people spent $321 on power for the AC. In other words, the average household is paying less now for AC than in 1989.

So here's the concern when it comes to household budgets and climate change: When something like this gets so much cheaper, it changes our behavior. But how?

Click the media player above to hear Marketplace Morning Report host David Brancaccio talk about what inflation can tell us about how we use energy.

Follow David Brancaccio at @DavidBrancaccio