Tamper-resistant outlets vs outlet covers: the outlet with shutters inside, or something on the outside

Three mechanisms

A tamper-resistant receptacle has spring shutters behind its slots that open only when both prongs push together; Leviton describes it as a shutter mechanism that blocks access to the contacts unless a two-prong plug is inserted. A sliding plate puts a similar shutter on the outside, on the wall plate, sprung to close when a plug is removed. A plug insert is a plastic plug with no prongs that fills the slots until someone takes it out. The first two protect without an adult doing anything; the third protects until it is removed, and it is designed to be removed. ESFI cites about 2,400 children a year treated for outlet injuries before TR receptacles were standard; the shutters are the fix the code chose.

Side by side

What each protects, and what it doesn't

All three protect an empty outlet from a probing object. None protects a plug that is in use: the TR shutters are open around the prongs, the sliding plate is held open by the plug, and the insert has been removed to make room. That gap is covered by in-use boxes, in best outlet covers for plugs in use. Where they differ is failure. A TR receptacle cannot be defeated by a child; a UL 498 listing stands behind it. A sliding plate can be jammed open by an over-tightened screw, and a determined child can sometimes slide the shutter with a flat object. An insert can be pried out, and then it is a choking hazard; that argument is made in full in plug inserts vs sliding outlet covers.

Cost and effort per outlet

A TR receptacle is a few dollars and fifteen minutes with the breaker off, per outlet, or an electrician for the whole house in a morning. A sliding plate is a few dollars and two minutes, breaker on. Inserts are under a quarter each and ten seconds. Over a house with twenty reachable outlets, the receptacles cost the most in time and least in worry; the plates are the reasonable middle; the inserts are cheapest and need the most supervision. Whether your outlets are already TR, which makes the whole question moot, is the subject of are outlet covers necessary.

Choose the receptacle if / choose a cover if

• Choose the TR receptacle if you own the home, are comfortable turning off a breaker and wiring an outlet (or will pay an electrician), and want the problem gone rather than covered.
• Choose the sliding plate if you rent, or wiring is not on the table, or the house has outlets you will not get to for a year.
• Choose inserts if it is a hotel, a grandparent's house for the weekend, or you already have TR outlets and want a visual cue. Then read best outlet covers for babyproofing for the rest.