Dad’s short answer: If anyone in the house has allergies or asthma, yes. Otherwise it's a nice extra. The catch is that a HEPA filter only helps if the whole machine is sealed — otherwise fine dust leaks out around the filter instead of going through it.

Sealed system is the part that matters

A HEPA filter captures very fine particles — dust mite debris, pollen, pet dander. But air takes the path of least resistance, and if the housing leaks, dusty air escapes through the gaps rather than the filter. You've then paid for a filter cleaning a fraction of the exhaust.

The phrase to look for is a sealed system, sometimes called whole-machine filtration: the airway from head to exhaust is gasketed so everything must pass through the filter. HEPA on an unsealed machine is mostly a sticker.

This is also why bagged machines tend to do better on allergies overall — the bag adds a filtration stage and contains the dust at emptying time.

Living with filters

Know which of your filters are washable and which are replaceable, because washing one that isn't meant to be washed ruins it. On a typical corded upright you'll have reusable foam filters you rinse, and a HEPA filter you replace roughly once a year.

Washed filters must be bone dry before they go back in. A damp filter smells and restricts airflow. I put mine out in the sun.

A clogged filter is the number one cause of "my vacuum stopped picking up." Check it before you conclude anything is wrong. Same story in every vacuum category I test.

Handhelds are worth flagging: plenty don't have HEPA at all and clog faster on fine dust as a result. Know that before you buy one for drywall dust or fireplace ash.

Dad’s Take: HEPA without a sealed system is a sticker. Ask about the seal, not the filter grade.