How to Get Some Sleep. Tonight.

So you screwed up. You forgot to buy an A/C, and you’re baking like a casserole. You need a unit delivered. Right. This. Instant. The bad news: Most stores offer next-day delivery at best. Bed Bath & Beyond promises same-day delivery for as low as $15, but be warned: They won’t actually install it. P.C. Richard says if you’re desperate, they’ll try hard to get a messenger to give you same-day service. Another option is simply to buy the A/C and call a messenger yourself. Though not all will handle big, bulky units, a few—such as RDS Messenger, Direct Rush Messengers, or Parkes Messenger—will deliver within Manhattan for about $40 to $100.

Still, getting it home is only half the battle: Now you have to install it. Most stores will do this for a fee, but if you can’t wait, call Mike’s Air Conditioning (718-257-1200), whose specialists will install for $95 and up, including complex custom jobs.

In your rush, don’t forget to make sure you’re getting a big enough unit, because—surprise—air conditioners are not returnable or exchangeable. So, do the math: Take the square footage of the room and multiply it by 35. That’ll give you the number of BTUs, or British thermal units, you’ll need. Consider getting a unit with intelligent energy-efficiency circuitry, which ramps down power usage when the room is cool enough.

Lastly, figure out how much noise you can tolerate. Panasonic makes the quietest units, but they sacrifice power and thus aren’t as cold. If you want a bedroom that feels like a meat locker, consider a high-end Friedrich unit, which pushes more air but is noisier. “Some people actually ask for the louder ones, because it drowns out the garbage trucks at 5 a.m.,” says Stanley Hank Saunders of P.C. Richard at Union Square.

If you’ve already got an air conditioner, consider getting it cleaned. Bacteria and mold grow inside, generating bugs that spill into your room and exacerbate allergies. “You’d vomit if you saw inside one of these things,” shudders Bill Saferstein of Bronx-based Air-Wave (212-545-1122). For $200 and up, he’ll pick up your unit, clean it, and reinstall it. And for true convenience, you can pay Air-Wave to pick up your air conditioner each year, store it over the winter like a fur coat, clean it, and deliver it fresh each spring. Now, that’s playing it cool.

How to Get Some Sleep. Tonight.