TechFuel HQPoE Power Budget Calculator: Will Your Switch Power It All?
Size a PoE switch for your APs, cameras, and phones. Add devices, cable length, and headroom to get the budget to buy — plus an 802.3af/at/bt reference.
PSE-side budgets: typical PD draws, cable loss and headroom.
PoE standards reference
| Standard | Name | Per-port at switch (PSE) | Usable at device (PD) |
|---|---|---|---|
| 802.3af | PoE (Type 1) | 15.4 W | 12.95 W |
| 802.3at | PoE+ (Type 2) | 30 W | 25.5 W |
| 802.3bt | PoE++ (Type 3) | 60 W | 51 W |
| 802.3bt | PoE++ (Type 4) | 90–100 W | 71.3 W |
A switch's PoE budget is the total wattage it can supply across all ports, measured at the switch (PSE) side. Device specs are usually the device-side (PD) draw, and the difference is lost in the cable — longer runs lose more, so this tool adds a length-based loss and a headroom buffer to recommend the switch budget you should actually buy. Per-device defaults are typical values; set your gear's real draw for accuracy. See the budget networking gear guide.
Worked examples
These are this calculator’s own outputs, computed with the same formula the tool runs in your browser — so you can see a real answer without touching a single input.
Small home network on the tool’s own defaults: 2 mid-range Wi-Fi access points at 13 W each and 4 fixed IP cameras at 8 W each, 20 m average runs, 20% headroom, switch budget left blank
- Inputs: ap-q = 2, ap-w = 13, cam-q = 4, cam-w = 8, ptz-q = 0, phone-q = 0, other-q = 0, len = 20, head = 20, budget = (blank)
- Result: Recommended switch budget 72 W (6 devices, +20% headroom); Raw device draw 58 W; Cable loss +2 W (~20m), 3% over the run.
Homelab with outdoor PTZ cameras: 3 access points at 13 W, 6 fixed cameras at 8 W, 2 PTZ/IR cameras at 20 W, 30 m average runs, 20% headroom, no budget entered
- Inputs: ap-q = 3, ap-w = 13, cam-q = 6, cam-w = 8, ptz-q = 2, ptz-w = 20, phone-q = 0, other-q = 0, len = 30, head = 20, budget = (blank)
- Result: Recommended switch budget 159 W (11 devices, +20% headroom); Raw device draw 127 W; Cable loss +6 W (~30m), 5% over the run.
Small office checking an existing 250 W PoE switch: 4 access points at 13 W, 8 fixed cameras at 8 W, 4 VoIP phones at 6 W, 25 m average runs, 20% headroom, existing switch budget 250 W
- Inputs: ap-q = 4, ap-w = 13, cam-q = 8, cam-w = 8, ptz-q = 0, phone-q = 4, phone-w = 6, other-q = 0, len = 25, head = 20, budget = 250
- Result: Recommended switch budget 174 W (16 devices, +20% headroom); Raw device draw 140 W; Cable loss +5 W (~25m), 4% over the run; Your 250W switch: Fits, 76 W to spare.
How to use this calculator
Enter how many of each PoE device you have — access points, fixed cameras, PTZ cameras, VoIP phones, and anything else — with the wattage each draws. Set the average cable run length and a headroom percentage, and the calculator returns the total switch PoE budget you should buy. Enter your switch’s actual budget too, and it tells you whether it fits with watts to spare or falls short.
The defaults are typical values; for an accurate result, set each device’s real rated draw (it’s on the spec sheet or the device itself).
Switch budget vs. device draw
A PoE switch advertises a total PoE budget — say 60 W or 250 W — which is the combined wattage it can deliver across all ports at once, measured at the switch (the PSE, power-sourcing equipment). Your devices (PDs, powered devices) are rated by what they consume, and the difference between the two is lost in the cable. So the budget you need isn’t just the sum of device labels: it’s that sum, plus cable losses, plus headroom. Size for the switch side, not the device side.
The headroom rule
Always leave room. Power-on inrush, an AP that ramps up under a full client load, a camera switching on night-vision IR, and underestimated cable loss all push real draw above the nameplate sum. About 20% headroom keeps ports reliable and leaves space to add a device later. A switch run at 100% of budget will start dropping power to ports the moment something spikes — usually as a confusing, intermittent outage rather than a clean failure.
What this pairs with
Once you know the budget, the budget homelab networking gear guide covers switches that hit common budget tiers, and the 10GbE on a budget guide is worth a look if you’re combining PoE with a 10GbE uplink. If your APs are the big draw, the Wi-Fi 7 guide covers which APs need PoE+/bt versus plain PoE.
Assumptions and sources
- The 802.3af/at/bt tier figures (15.4 / 30 / 60-90 W sourced at the switch, 12.95 / 25.5 / 51-71.3 W delivered at the device) are the IEEE PoE standards’ numbers: 802.3af (Type 1), 802.3at (Type 2), and 802.3bt (Types 3 and 4, published as IEEE 802.3bt-2018, which the IEEE sells rather than publishes openly). The Fluke explainer previously cited here for the same figures now redirects to Fluke’s blog index and no longer carries them, so it was dropped on 2026-08-14 rather than left standing as a source that supports nothing.
- The default device draws (13 W mid-range AP, 8 W fixed camera, 20 W PTZ, 6 W phone) are TechFuelHQ typical values, stated so you can replace them with your gear’s rated draw from its spec sheet - which the page recommends for an accurate budget.
- The distance-based cable-loss model (rising to roughly 15% near a 100 m run, applied as
deviceW / (1 - loss)because loss is a fraction of what the switch sends) and the 20% headroom rule are TechFuelHQ working assumptions. The 100 m case works out to a x1.176 markup, which matches the IEEE ratios in the table above - 802.3at is 30 W at the switch for 25.5 W at the device, and 802.3bt Type 3 is 60 W for 51 W. Until 2026-08-30 the model multiplied by (1 + loss) instead, topping out at x1.15 and so sitting under the standard this page prints, in the under-powering direction.