🔌 Halloween Decoration Power Budget

The load. Every appliance's rated wattage is added and scaled by the proportion running at once. That matters: a fog machine cycles its heater, while a projector and a blower run continuously. Add up the labels, then be honest about which ones are on together — Christmas and Halloween displays usually trip a breaker in the first hour of the first cold night.

Current and headroom. Current is watts divided by volts. A 13 A socket is not a 13 A target: continuous loads are normally kept to about 80% of the breaker or socket rating, so the planner shows the headroom that remains and flags anything above it. The existing load on the circuit matters too — the decorations share the ring main with whatever else is plugged in.

Voltage drop. For a copper lead, drop ≈ 2 × length × current × 0.0175 ÷ cross-section, with length in metres and cross-section in mm². The factor of two accounts for the out-and-back path. A 20 m, 1.5 mm² lead carrying 7 A loses about 3.3 V, or 1.4%, which is fine; a 40 m, 0.75 mm² lead carrying the same current loses over 13 V and gets warm. Above about 5% the props dim and motors strain; the cable's current rating matters more than the drop.

Cost. Energy is kilowatts × hours. Multiply by the nights on display and the tariff on your bill (the default is a recent UK-style figure, not a promise). The biggest saving is usually the blower left running after the last visitor, not a new set of bulbs.

Last reviewed: 2026-10-20. A planning estimate, not an electrical installation design. Use RCD-protected outdoor sockets, keep connections out of standing water, and follow local wiring rules.