We have a dog. We have a kid. Our carpet has seen things. Spilled milk, muddy paw prints, something brown I chose not to identify. After renting a carpet cleaner from the grocery store four times in one year, I did the math — I had spent enough on rentals to buy a machine outright.

Here is what to look for, plus a few machines that punch above their weight.

What Matters in a Carpet Cleaner

• Suction power. This is the whole game. Strong suction pulls dirty water out of the carpet so it actually dries in a few hours. Weak suction leaves the carpet damp, which leads to mildew smell.
• Brush roll. Rotating brushes scrub the carpet fibers. Look for machines where the brush roll can be removed and cleaned — pet hair wraps around it fast.
• Tank size. Bigger tanks mean fewer trips to the sink. But bigger machines are heavier. If you have stairs, lighter is better.
• Hose and attachments. You need an upholstery tool for furniture and a crevice tool for edges and stairs. Most machines include these; check before you buy.

Best Overall: Bissell ProHeat 2X Revolution Pet Pro

Designed specifically for homes with pets. The brush roll has rubber nubs that grab pet hair. Heats the cleaning water (warm water cleans better than cold). Two separate tanks — one for clean water, one for dirty — so you are not pushing dirty water back into the carpet. About $250.

Best Budget: Hoover PowerDash Pet

Compact, lightweight, under $120. The small tank is annoying if you are doing multiple rooms, but for spot cleaning and one room at a time, it performs well above its price. Great for apartments.

Best Portable: Bissell SpotClean ProHeat

Not a full-size machine — it is a spot cleaner. Hose and hand tool only, no upright push mode. But for car upholstery, stairs, and pet accidents on furniture, it is the tool you actually use instead of putting off until the weekend. About $160.