Can Google conquer television? Yesterday, I talked with Keval Desai, product manager for Google’s TV Ads unit, and he did a pretty good job convincing me that it can.

“TV is becoming like the Web,” Desai says. From an advertiser’s perspective, he has a point. In the 1980s, a popular TV program like The Cosby Show might have captured half the viewers in the entire United States; today’s most popular shows, like American Idol, are lucky to capture a fourth of the whole audience. The difference is that there are dozens of channels now, each catering to a different set of viewers. As Desai notes, this is a lot like the Web: the audience is out there, but it’s split into small bits consuming a wide variety of content.

So Google’s TV Ads system works much like AdWords. An advertiser selects keywords and sets a spending limit for each day (per thousand people who see the ad). The system then figures out where and when the ad should be placed. Google is borrowing another trick from Web advertising: a soon-to-be-launched feature that lets advertisers search for shows based on audience demographics (a feature inspired by Google’s search-based ad targeting).

The service is clearly aimed at a different kind of television advertiser. In addition to a simplified user interface, TV Ads includes instructions on how to visit Google’s marketplace and find someone who can help make an advert. Indeed, Desai says, the plan is to draw in advertisers who don’t normally put ads on TV and, as a complement, bring ad dollars to networks that don’t normally have broad recognition.

The TV Ads interface already lets you select target shows based on audience age and gender information, which is in turn based on data from a partnership with Nielsen. But Desai told me about a partnership that will take this farther. A satellite-TV company called Echostar, working with credit-reporting company Equifax, will cross-reference shows watched (using its own data from set-top boxes) with income and buying habits (using Equifax’s data). This will let Google offer shows to advertisers that will reach, for example, people with household incomes greater than $100,000. Desai stresses that all this data is made anonymous, so it certainly won’t be possible to target specific households with ads.

I wonder how long we’ll have to wait for that.