Power & electrical
How to Know When Your RV Loses Shore Power — Before It Matters
Search any RV forum for "shore power alert" and you'll find the same thread, written over and over by different people: "Alert/Alarm for Losing Shore Power???" "Power Outage Alert." "How To Know When Shore Power Is Lost." The question has been asked on iRV2 for years, and the answers never satisfy, because the honest answer is uncomfortable: there is no great off-the-shelf product for this. There are workarounds — some clever, some fragile — and this article walks through all of them. But first, why this question keeps getting asked.
Why losing shore power is invisible
Here's the cruel design irony of a modern RV: the better your electrical system, the less you notice a power failure.
When the pedestal drops, your inverter does exactly what you paid it to do — it takes over instantly and silently. The lights stay on. The TV keeps playing. The residential fridge keeps humming on battery. Nothing beeps. Nothing flashes. From inside the rig, the moment shore power dies is literally imperceptible.
What the inverter can't carry is the air conditioner. On most rigs, the AC dies the instant the pedestal does, and a clock starts ticking that nobody announced. On a hot afternoon, an RV interior can climb to dangerous temperatures in well under an hour — and if your dog is asleep on the dinette while you're out to dinner, that clock is the only one that matters. (We cover the heat timeline in our pet safety and temperature guide.)
This is why power-loss alerting beats temperature alerting. A temperature alert tells you the RV is already hot. A power alert tells you it's about to get hot — often 30 to 45 minutes earlier. In the pet scenario, that head start is frequently the whole outcome.
All the ways a pedestal fails you
Five failure modes, one common thread: only one of them is "the whole campground went dark," and a standard RV reports none of them.
Campground power dies in more ways than most owners expect, and only one of them is "the whole campground went dark":
- A tripped pedestal breaker. Two ACs, an electric water heater, and a convection oven will find the limit of a tired 30A breaker on a 95°F day — exactly the day it matters.
- A campground-wide outage. Heat waves knock out whole parks precisely when every rig is running max AC. The campground office knows; you, at a restaurant twenty minutes away, do not.
- A worn receptacle. Decades of plug cycles leave pedestal receptacles loose and heat-damaged. A connection that worked at check-in can fail — or arc intermittently — days later.
- Another RVer unplugs you. It sounds paranoid until you read the forum threads. Confused neighbors, kids, and campground staff have all starred in this story.
- Your own EMS disconnects you — correctly. A quality surge protector/EMS is supposed to cut power on low voltage, an open neutral, or a wiring fault. You want it to. But an EMS that protects your rig silently is still an AC outage as far as your pets are concerned. (If you don't run one yet, start with our surge protector and EMS guide — the one device category we consider non-negotiable.)
Notice what's common to all five: nothing in a standard RV tells you any of it happened. So RVers improvise.
The workarounds RVers actually use — honestly assessed
None of these was designed as the complete answer; all are pressed into service anyway. Here's each, with its real failure modes.
1. A cellular monitor with power-loss alerts (MarCELL is the standout)
The most direct commercial answer is a cellular monitor that treats power loss as a first-class alert, and MarCELL is the best example we've found: it checks power every 10 seconds and pushes a power-lost notification by text, call, or email, keeps reporting on its internal battery for up to 48 hours, and tells you when power returns. Plans start at $8.25/month, in Verizon and AT&T versions to match your campground's actual coverage.
The honest catch: MarCELL watches the outlet it's plugged into — the RV side, not the pedestal side. Fine for the common case (pedestal dies, RV outlets die, alert fires). But if your inverter feeds the outlet MarCELL lives on, the inverter's seamless takeover fools the monitor exactly the way it fools you. It has to go on a non-inverter-backed circuit — which may take a wiring diagram, or some outlet testing with shore power pulled, to identify. Get that one detail right and this is the best plug-and-play option going. See how it stacks up against Waggle, Temp Stick, and the rest in our full monitoring system comparison.
2. Hughes Power Watchdog + RV Whisper
The Hughes Power Watchdog is a surge protector/EMS that sits at the pedestal and watches voltage, amps, and faults over Bluetooth — sensing exactly the right thing, on exactly the right side of the plug. The problem is Bluetooth's range: brilliant at the campsite, useless from a restaurant.
Hughes and RV Whisper offer a pairing that bridges the gap — an RV Whisper monitor station reads the Watchdog over Bluetooth (Gen II Watchdogs can also report over their own WiFi) and relays its data to the internet, so you can see pedestal-side power from anywhere and get text or email alerts when it changes. (Hughes sells the station under its own name as the RVM21S, so this is a supported alliance, not a hack.) Architecturally, this is the most correct workaround on the list: it monitors the pedestal itself.
The honest catch: the relay chain needs campsite internet, a powered RV Whisper hub, and two products from two companies staying friends. Every link is a place the alert can silently die — and the internet link usually depends on the same power that just failed, unless your router is on battery backup too. It works, owners like it, and Hughes selling the station as the RVM21S makes it official — but official doesn't shorten the chain, and chains fail at their weakest link.
3. Generator auto-start as an accidental alarm
Owners of rigs with automatic generator start (Onan EC-30, Magnum AGS, or SilverLeaf's Rozie web remote on RV-C coaches) have discovered a side effect: set the AGS to fire on low battery voltage, and a shore power failure eventually starts the generator — keeping the AC alive and functioning as a very loud, very expensive notification. Some Rozie users on iRV2 run this explicitly as their pet-protection backstop.
The honest catch: it's not an alert, it's a delayed response — plain AGS sends you no message at all, and even Rozie owners, who can at least check status on the web, get no shore-loss push. The generator starts when the battery sags — potentially hours after the pedestal failed, hours your AC wasn't running. Set the voltage threshold too high and the generator cycles constantly; too low and one day it doesn't start at all. A genuinely good backstop for motorhomes that have it — but not a monitoring system, and you still won't know anything happened until you come home to a warm generator.
4. A smart plug + phone automation
The budget hack: put a WiFi smart plug (or a purpose-built device like a MySpool power-failure alert, which texts on power-off and power-restored with no subscription fee) on a shore-power-only outlet, and let "device went offline" become your outage signal — via the vendor's native alert or a phone automation that pings you when the plug drops off the network. One iRV2 owner reports MySpool texting them within 30–60 seconds of an outage, with the router deliberately kept on an inverter-backed circuit so the alert can still get out.
The honest catch: this inverts the problem into keeping the network alive while the power is dead. The router must be on battery or inverter power; the plug must not be. (That's the same wiring caveat MarCELL carries — neither device truly senses the pedestal side; both infer it from an outlet that dies with shore power.) And "offline" alerts are infamous for false positives — every WiFi hiccup looks identical to an outage, and after the fifth false alarm most people mute the notification that was the entire point. Cost: $10–25 for a generic WiFi smart plug. Reliability: exactly what you'd expect at that price.
5. The DIY route: Home Assistant + a Shelly sensor
For the tinkerers: a Shelly relay or plug on a shore-power-only circuit, reporting to Home Assistant, with an automation that fires a critical phone notification the moment mains power disappears — pushed over a cellular router or Starlink, with the whole stack on a small UPS or the house battery. Done right, this checks all three boxes — it senses the right circuit, survives the outage, and alerts you anywhere, with no subscription beyond your connectivity — provided you build and maintain every link yourself.
The honest catch: done right is load-bearing. You're the integrator, the electrician, and the on-call engineer, and the system is precisely as reliable as your weakest automation. But it's the only approach here where every failure mode is at least yours to fix. Our complete smart RV Home Assistant guide walks through the full build, including this exact automation.
What a real solution would require
The three-box test. Run the five workarounds against it and the pattern is stark: no off-the-shelf product checks all three.
Strip the problem to its essentials and a trustworthy shore-power alert needs exactly three things:
- It senses pedestal-side power — not an interior outlet the inverter can quietly backfill.
- It has its own battery — the event it exists to report is, definitionally, the loss of its power supply.
- It has its own cellular path — campground WiFi is unreliable on a good day, and on the day power fails, your router may be dark too.
Run the five workarounds against those boxes and the pattern is stark. MarCELL has the battery and the cellular radio but senses the wrong side of the plug unless you wire around it. The Watchdog senses the right side but depends on borrowed internet. The smart plug fails two of three. The AGS isn't an alert at all. Only a carefully built DIY stack checks all three — and only because you personally assembled each box.
The gap, stated plainly
We'll say directly what the forum threads dance around: shore power loss alerting is the biggest unsolved problem in RV monitoring. It's the failure that starts the most dangerous common scenario, it's invisible by design, and after years of RVers asking, no off-the-shelf product senses the pedestal, carries its own battery, and carries its own connection. Everything above is a workaround — and the fact that thousands of owners maintain these Rube Goldberg alert chains is the clearest possible evidence that the actual product is missing.
What to do today, by camper type
- Traveling with pets: a cellular monitor with power-loss alerts (MarCELL first, on a non-inverter outlet) plus temperature alerting as the backstop. The one profile where we'd say don't wait — do it before your next trip.
- Motorhome with auto-gen-start: AGS on low voltage as your response layer, a cellular monitor as your notification layer. They solve different halves.
- Seasonal/long-stay site with good WiFi: Watchdog + RV Whisper gives the richest pedestal-side picture, if you accept the internet dependency.
- Rig in storage: power alerting matters less than battery and temperature — a different problem, covered in our storage monitoring guide.
- Tinkerers: the Home Assistant build is the only path to all three checkboxes today. Budget a weekend.
FAQ
How do I know if my RV loses shore power while I'm away? You won't — not from the RV itself. Modern rigs fail silently because the inverter bridges the outage. You need a device that notices for you: a cellular monitor with power-loss alerts (on a non-inverter-backed outlet), a pedestal-side EMS with an internet relay, or a DIY sensor with its own alert path.
Does an inverter mask a power outage? Yes — that's its job. It switches over in milliseconds so your electronics never blink. Lights, TV, and residential fridges keep running; the air conditioner, which the inverter can't sustain on most rigs, quietly dies. That's exactly why outages go unnoticed.
Will my surge protector alert me if power goes out? At the campsite, often yes — Bluetooth EMS units like the Hughes Power Watchdog show faults and voltage on your phone within range. From across town, no — Bluetooth doesn't travel. You need something to relay it to the internet, like the RV Whisper pairing, and that relay needs power and connectivity of its own.
What is the best RV power outage alert device? For plug-and-play, MarCELL is the strongest option we've found in owner reports — dedicated power-loss alerts over cellular with up to 48 hours of battery. Its blind spot: it must live on an outlet the inverter doesn't back up. For pedestal-side sensing, Watchdog + RV Whisper; for full control, DIY Home Assistant. No single device does it all — see our full comparison.
What is RV low voltage protection? An EMS function that disconnects your rig when pedestal voltage sags below a safe threshold (typically ~104V), protecting air conditioners and electronics from brownout damage. Worth having unconditionally — just know a protective disconnect is also a power outage you won't hear about unless something tells you. Details in our EMS guide.
Bottom line
Losing shore power is the most consequential silent failure in RVing: common, invisible by design, and the start of the clock on the scenario every pet owner dreads. Today's honest answer is a layered workaround — a cellular monitor on the right outlet, an EMS at the pedestal, maybe a generator or DIY stack behind them — because the purpose-built device genuinely doesn't exist yet. Pick your layer, test it by actually pulling the plug at the pedestal (the test almost nobody runs), and know exactly which box your setup doesn't check.
[Disclosure placeholder: once Waystation launches, add — "We're building an RV monitoring product ourselves, which is why this gap is the problem we think about most. This guide reflects owner reports and published specs; we've marked every place our judgment could be biased."]
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