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Wi-Fi Battery Life Calculator
How long a battery-powered Wi-Fi sensor lasts — and why how it connects matters far more than what it sends.
1 · Your device
Payload size is not an input: over Wi-Fi the message itself is free. What costs charge is the connection wrapped around it.
MacSync WT One — temperature · every 15 min
2.94years
0.148mAh
Charge per message
35,040
Messages per year
627µA
Average draw
Where the time goes
3.30 s of radio for one message
The publish itself is the small bar. Everything else is overhead — which is why shrinking the payload does almost nothing for a Wi-Fi sensor, and why the two dropdowns above are worth more than any amount of firmware tuning elsewhere.
To hit your target
Tune the connection
Same device, same 15 min interval. Only how it joins and secures the link changes.
Best here is 14.3 years against your current 2.94 — a 4.8× difference from firmware settings alone, with no hardware change. Dropping TLS is listed for comparison but is rarely the right trade; resumption gets you most of the saving and keeps the encryption.
Deep sleep or stay connected?
2.94
years — deep sleep between messages
1.14
years — stays associated with the AP
Holding the association means waking for every DTIM beacon, which averages about 1 mA — three orders of magnitude above deep sleep. It is the most common reason a battery Wi-Fi sensor dies in months instead of years. Only stay connected if the device genuinely has to receive commands within seconds.
Would LoRaWAN be better?
Usually, for a battery sensor reporting on a schedule. A LoRaWAN uplink costs roughly 0.017 mAh against 0.148 mAh here, because it never has to associate, get an address or negotiate a session — it simply transmits.
Wi-Fi earns its keep when the infrastructure already exists, the data rate matters, or the device is near mains anyway. For a sensor on a cell, reporting every few minutes, the gap is years.
How these numbers are calculated
The session, not the payload — each message costs wake + sensor read + association + TLS + publish + teardown. Over Wi-Fi the publish itself is microseconds of air time, so payload size is deliberately not an input. Multiply the session charge by messages per year, add idle draw across all 8,760 hours, add cell self-discharge, and divide into usable capacity.
Connection timings — a stored BSSID, channel and static IP restored across deep sleep is measured at under 200 ms; DHCP typically costs 1.5–2 s and considerably more when the server is slow. A full TLS handshake takes roughly fourteen times the energy of an unencrypted exchange; session resumption avoids nearly all of it.
Cross-check — an unoptimised wake-connect-publish cycle is widely measured at 3–5 s of radio at about 160 mA, or roughly 0.2 mAh per message. The phase model reproduces that for the DHCP plus full-TLS path, which is what tells us the individual timings are sane.
These are typical figures, not Macnman measurements — unlike our LoRaWAN range data, connection timings are not on any specification sheet and depend heavily on your access point, network load and broker. Treat the ratios between options as reliable and the absolute years as an estimate until measured on site.
Service life is capped at 20 years — Li-SOCl₂ cells are rated for roughly 20–25 years regardless of how little current you draw.
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