Home Electric Fences by Perimeter

Residential Electric Fence Sizing

For Brazilian homes, an electric fence is hard to beat on cost as an active perimeter deterrent. It goes on top of an existing wall or on its own posts. To work out how much wire you need, use total_wire = perimeter × wires. You typically run 8 to 10 horizontal wires spaced about 20 cm apart, which adds 1.6 to 2.0 meters of vertical fence above the wall.

The central energizer (“central de choque”) sends out pulses of 8,000 to 10,000 volts, but at amperage so low that the shock hurts and disables without being lethal. That matches what CONTRAN and ABNT NBR 15983 (the Brazilian standard for residential electric fences) require. The law also says you need warning signs (“Cuidado: cerca eletrificada”) every 25 meters along the perimeter, plus one at each access gate. On top of that, the install has to have grounding rods at least 1.2 m deep and a panic button you can reach from inside the house.

Applications

You see these on house walls, condominium boundaries, commercial buildings, rural plots, and around roof access points. ICVE (Instituto de Certificação de Cercas Eletrificadas) handles certification of installers and equipment. The brands you run into most often here are Genno, Intelbras (ELC), JFL and ECP. Size the energizer to your perimeter: a single-zone unit handles up to 1,000 m of total wire, while multi-zone industrial gear goes past 5,000 m.

FAQ

Is the shock dangerous to humans or pets? Each pulse lasts 1–3 milliseconds at very low current (under 5 mA). It makes muscles contract but won't burn you or pose a cardiac risk if you're healthy. Even so, keep the warning signs up and keep kids away. Anyone with a pacemaker should never touch the wires.

Does it work during a power outage? Yes. Every certified energizer carries a 12V backup battery (sealed lead-acid, 7–12 Ah) that keeps the fence live for 4 to 12 hours. Some models will also set off a siren if someone cuts the wires.

Do I need permits or condo approval? A standalone house usually won't need a municipal permit, but condominiums and shared walls do require sign-off from the neighbors. Hire an installer registered with CREA or ICVE so the job meets NBR 15983 and your insurance stays valid.