When the star Sirius appears in the night sky, it officially kicks off the "dog days of summer," 40 of the hottest, stickiest days of the year. They extend from July 3 to August 15. This year, with energy costs at an all-time high and expected to keep on rising, it's an excellent time to beat the heat and high energy bills by buying a new air-conditioning system. Today's high-efficiency models with a federal energy star label use half the energy of a 20- year-old model. And, during peak cooling periods, you can cut overall energy bills 20 percent to 40 percent. Units 10 years old or older have seasonal energy-efficiency ratings (called S.E.E.R.'s) of only 6 to 8. New units are rated 12 to 14 -- or greater. With new higher S.E.E.R. energy star efficiency, you'll see a big difference and big savings. And, many utilities now offer rebates on these units, too. For more tips, visit our Web site at onthehouse.com. And that's the On The House tip for today.