Skip to content

Smart Home Load Calculator

Calculate total electrical load from smart home devices, PoE budgets, and UPS sizing

Reference Info & Formulas
PoE Standards

PoE (802.3af): 15.4W per port

PoE+ (802.3at): 30W per port

PoE++ (802.3bt): 60W / 90W per port

Most cameras and APs use PoE or PoE+

Typical Smart Home

3-bed house: 80-150W total smart device load

Well within a single 16A circuit

Most smart devices use minimal power

Smart Devices
Enter quantity of each device type

12W active, 12W standby

2W active, 0.5W standby

8W active, 8W standby

15W active, 15W standby

5W active, 5W standby

10W active, 3W standby

15W active, 5W standby

15W active, 15W standby

50W active, 50W standby

5W active, 5W standby

5W active, 1W standby

25W active, 25W standby

Custom Devices
Add devices not listed above
Options
UPS and PoE calculations

Data: Manufacturer specifications, IEEE 802.3af/at/bt, BS 7671

For guidance only. The responsibility for any electrical installation lies with the qualified person carrying out the work. Always verify calculations independently and apply professional judgement.

How This Calculator Works

The smart home load calculator sums the power consumption of all smart devices to determine total load, PoE budget, UPS sizing, and circuit requirements.

Each smart device has an active power rating (when in use) and a standby power rating (when idle). The calculator sums both to give you worst-case and typical power draws. PoE devices are separately totalled to determine the required PoE switch budget, and UPS sizing accounts for the full active load with a 20% safety margin.

Annual cost = ((Active_W x Active_hrs) + (Standby_W x Standby_hrs)) x 365 x Rate / (1000 x 100)
Active_W
= Total active power of all devices (W)
Active_hrs
= Hours per day devices are actively used
Standby_W
= Total standby power of all devices (W)
Rate
= Electricity unit rate (p/kWh)

PoE budget = sum of all PoE device wattages (at 48V DC)

The circuit recommendation is based on the total active load. Most smart home installations fall well within a standard 16A circuit. The calculator flags if the total load exceeds 500W, at which point a dedicated circuit may be worth considering for reliability and ease of maintenance.

Quick Reference \u2014 Smart Device Power Consumption

Typical smart home device power ratings

Manufacturer specifications (typical values)
DeviceActive PowerStandby PowerPoE
WiFi Access Point12W12WYes (PoE)
Smart Switch/Dimmer2W0.5WNo
IP Camera (Indoor)8W8WYes (PoE)
IP Camera (Outdoor)15W15WYes (PoE)
Video Doorbell5W5WNo (battery/transformer)
Smart Speaker10W3WNo
Network Switch (8-port)15W15WNo
NAS/Server50W50WNo
PoE Lighting Panel25W25WYes (PoE++)

Actual power consumption varies by manufacturer and model. Always check the device data sheet for the specific power rating.

Practical Notes

PoE Switch Sizing

Always buy a PoE switch with at least 20% more budget than your current total PoE load. This allows for future expansion and accounts for the fact that some devices may briefly draw more power than their steady-state rating (e.g., during camera IR illumination at night or PTZ motor operation). A 120W switch comfortably handles most 4-6 camera installations.

UPS for Network Infrastructure

A UPS on your core network equipment (router, PoE switch, NAS) keeps your entire smart home operational during brief power cuts. This is especially important for security cameras, alarm systems, and any automation routines that need network connectivity. A 500VA UPS typically provides 30+ minutes of backup for a network rack.

Neutral Wire Requirements

Many smart switches and dimmers require a neutral wire at the switch position. Older UK lighting circuits often only have line and switched live at the switch. Before specifying smart switches, check the wiring at each switch position. Some "no neutral" smart switches exist but require a minimum load and may flicker with very low-wattage LED lamps.

Frequently Asked Questions

SparkyHub is a free resource built by Taro Schenker — I build websites for trade businesses too.

Related Calculators

Lighting Circuit

Cable sizing for lighting with inrush current

Max Demand

Calculate total maximum demand after diversity for the EIC

UPS & Generator

Size UPS, generator, and battery for critical power

Electricity Cost

Calculate how much it costs to run any electrical appliance

Built by Taro Schenker · Need a website for your trade business? Get in touch