1/10 Second Power Outage = Sense Offline


Had a quick power outage again on Sunday 9/24 just before 9 AM. Didn’t check sense until just now and it’s been offline since that power blip. Looks like the AP did get power cycled this time.

Should I not have received notification that it was offline or did that feature not come until 9/25?


@KHouse75, that feature wasn’t released until the morning of 9/25 so you wouldn’t have gotten a notification if the outage was before then.


We had a freak (for Georgia) snowstorm come through last Friday night and had lots of intermittent power service issues (enough to make the UPS beep a few times, but not enough to have the TV, roku, oven, microwave, or anything else with a capacitor reboot).

Each and every time the power fluctuated, the sense unit went offline (at least 6 times). Where does this issue stand with engineering? Is there a possibility of an external power source? Battery? Capacitor on the power input? Power over ethernet (or ethernet in general)? This unit continues to demonstrate that it’s a really neat toy but just not reliable enough to be used in any serious installation.



Any updates on this issue? I can now confirm that the “device offline” notification is working, as my Sense monitor crashed twice yesterday during the windstorm that affected us in the northeast. We had about five power drops lasting from ~200ms to 2 seconds before we lost power entirely. Sense went offline after two of them. I had to turn the breaker off and back on to bring it back to life. Is there no hardware watchdog in this thing??


Hey @pswired - sorry about this! Hope you faired ok in that Nor’easter.

These kind of brownout and power outage conditions are still a known issue without a simple solution unfortunately. The hard reset you mentioned is the best workaround. Hopefully this doesn’t happy too frequently for you, but if you are in an area that frequently experiences brownouts or outages, please reach out to the support team to see if they may be able to offer some additional workarounds.

So sorry for the troubles!


Thanks, Brad. I don’t have frequent power outages, so this isn’t a major problem for me, but I am away from home a lot, and one of the major benefits I get from Sense is the ability to remotely keep an eye on important devices like my furnace and sump pump. I can’t do this if it’s gone offline from a power blip.

Also, all of my wireless APs, my router, and ISP equipment is battery-backed, so in my case there shouldn’t be any networking issues regardless of what the utility power is up to. I have a fiber-based primary ISP and satellite backup, so there should be no link between utility outages and ISP failures.


You’re right, the problem is on us to think about some future solution that can offer battery backup, or a juicy capacitor to help bridge the gap during very quick power outages. There have been some great suggestions here. Unfortunately, we have some customers with really nasty power situations where they experience brownouts every day, and their Sense has a hard time recovering. They are understandably pretty frustrated. Best case is actually a full power outage that gives Sense a chance to restart from scratch.

We’ll be sure to update this thread as we learn more, and thanks for everyone’s patience in the meantime!


Any updates, @BradAtSense? Another round of storms rolled through this evening and knocked my Sense offline when a utility recloser cycled. Doesn’t your hardware have a way to implement a CPU watchdog?


If we have a residential power outage, the SENSE monitor quickly restarts before the internet and WiFi connection has been re-established. The SENSE software is not robust enough to reconnect later if WiFi (or internet) is not present (or available) during the reboot phase. When we have a neighborhood power outage, it affects our ISP neighborhood hubs along with our home network. It takes time for the internet and WiFi connections to be re-established at all the different locations. I know there is a lot of competing traffic on the internet just after power is restored. All of my home network devices are working to reconnect to remote servers (plus the neighbor’s).

My Solution:
I installed an “On-delay Timer relay” that powers the SENSE unit. If power is lost, then the timer waits for 8-minutes (or some adjustable time) before restoring the power to the SENSE monitor. During this wait period, the internet has time to re-connect and re-establish the communications link before SENSE powers up. I lose about 10-minutes of data (8-minutes for the delay, 2-minutes for SENSE to reboot and reconnect), but not hours or days of data.

The Device:
My brother built this device using parts that were laying around in his garage. There are more elegant solutions. Basically it’s a SPST (Single-Pole, Single-Throw) 0-8 minute ‘Delay-timer’ connected to a DPDT relay. You can purchase a DPDT (Double-Pole, Double-Throw) ON-Delay timer relay that tests both legs for voltage that has more options for the timer and all the features are built into the relay for around $60.

Now after I have a power outage, I do not have to go manually reset the breaker that SENSE is attached to in order to establish internet communications. Yes, I lose 10-minutes of data, but that is better than losing hours, days or weeks of data if I am not home to manually restart the SENSE monitor. I started with the maximum delay setting and will test for shorter time delays. I have attached some photos.

Parts and Wiring:


Offline 13 times this year
Sense Offline after Power Outages

Delay relay is a nice solution. But I am having a hard time believing that whatever SoC the sense is using doesn’t have some sort of onboard watchdog timer that will reset the system when it gets into whatever unknown state these power fluctuations cause.

At least in my case, the issue is not with reconnecting to an unavailable WiFi or Internet connection as those are not interrupted when the power goes out for me.


You can do the same setup but with a small standby ups. During a power outage, the ups flips to battery during which time, watts calculated will be based on the voltage supplied by the UPS batteries and not line voltages. When the power comes back on, a switch internal to the ups flips to A/C power only. Keep the WiFi access point on battery as well.


I can place a UPS system on my home network parts, but that does not fix the problem where my internet provider’s hubs are down. The ISP hubs (which are external to my home) have to reboot and reconnect. That takes time. How much time, I am still working to figure out. I am sure there are multiple solutions to similar problems. The only other solution I can envision is that SENSE Support writes a software routine for the SENSE monitor that correctly works to establish WiFi connection after the unit has rebooted so that a manual reset at the breaker panel is not necessary. That hasn’t happened and it did not appear to me that it was going to happen.

My point was to share my experience so someone else might benefit.


I just chatted with one of our engineers about this and we do have a CPU watchdog. If you write into support@sense.com they can take a look at your logs and see exactly what’s happening on your end. And @Dcdyer if you’re finding that your delayed relay solution isn’t working well enough (but really cool solution!), I’d suggest you do the same.


I had already turned in tickets:



I did receive replies from the Support team. I think the tickets have been closed. The problem was they interpreted my problem as something different than what I was trying to explain. At this moment, my ‘On-delay timer’ is working successfully. I lose 10-minutes of data after a power outage, but I don’t have to go to my breaker panel and manually reset the breaker to make the SENSE monitor connect to the WiFi. I’m still interested in finding a better solution, but I guess I gave up on SENSE support finding a software solution, so I developed a hard-wired solution.

I have lengthy emails giving the Support team all types of personal data. Thanks for taking the time to respond.

My suggestion is to use the “Six Sigma process” methodology to find solutions to the issues that SENSE customers are having. Maybe you are already doing this, but haven’t allowed the customer community to see it in action. I see a lot of individual blogs where people are voicing their frustrations but there are no tools in place for the customer to measure the frequency of problems or small things like their WiFi connection strength. Unless you provide standardized tools (from SENSE) that can replicate the same measurements for every SENSE customer, then you are going to keep seeing frustrated customers. When I read through the customer blogs, it feels like the ‘wild west’. Everyone is using a different tool and giving you their opinions. There is no standardized set of tools with data.

Write more documentation! Or get @Kevin1 (a customer) to write it for you. He is a very knowledgeable customer. Or put a team of “super customers” together to write missing documentation (helpful personal hints, etc.). @NJHaley has a lot of prior history and has answered numerous customer questions that should have been included into an “Advanced User document”. You are missing out on an opportunity to “crowd source” the knowledge from people who are willing to help the company succeed.

Thanks for listening. I’m certain you are already getting too many suggestions from customers, more than you have time to read. Don


When I started this topic, initial impressions were that this doesn’t seem to be an issues with WiFi or internet connectivity being unavailable when a quick power flicker occurs. I think that is still the case. I’ve had several instances where the power flickered and sense stopped working but my cable modem, access points, and network switches never went offline. None are on UPS. Power cycling the access point used by sense didn’t help. Only power cycling sense fixed the problem.

I’ve had a few occasions where the power went out for longer than a few seconds and everything turned off. I takes a few minutes for the cable modem to boot, sync and come online. It then takes a little while longer for my firewall to obtain an IP address from the ISP. I’ve never once had sense not connect up when this happens.

I’ve also had many occasions where my internet connection went down for an extended period of time and sense always connects back up and fills in missing data as it caches several hours internally.

Since I haven’t had to power cycle my sense in a really long time, I thought maybe the problem had been resolved and I never explored using two UPSes. If it does happen again, I will pick up a couple of inexpensive UPSes and will wire the sense into them and we’ll see what happens.

I also have a Smappee and have never once had to power cycle it for any reason. It always connects back up. I think Sense is far superior in almost all ways. However, I do like that I can monitor both my power panels using one Smappee device and four CT devices connected with a Y cable.


I don’t understand these suggestions that sense can be wired to a UPS. The power input for the sense monitor is 240v and is used for voltage sensing to do power calculations. I’m not aware of 240v 60hz UPS units, especially in the sizes needed here. And even if one were to attach two small 120v single phase UPSes to separate legs and connect both to the sense monitor, I can imagine the havoc that would ensue when they drift out of sync. Plus many UPSes have AVRs and other components that would affect the sense monitor’s voltage reference.


You’d have have to use 2 ups devices. Most UPSes you use in the home are just simple bypass devices. They have a contact switch that flips between line and battery. When on line, it’s straight line typically. I’ve tested the other way around where devices are plugged into APC standby UPSes and they are detected with no issues. Same with power conditioners. No issues with sense detecting the devices plugged into them. There is no buffering of the energy consumption so nothing to change what sense sees when devices use energy through a standby UPS or Power Conditioner.

I thought I explained somewhere here a while back about how to go about using 2 UPSes.

See my post below for more information on what the two 120 connections to sense actually are used for.


One very important thing I forgot to note above is that sense is only using the two 120V phases to monitor voltage and to supply a small amount of electricity to sense for it to operate. It then takes that voltage for each phase and multiplies it with the amps detected with the CT sensors to determine watts used. Nothing else is done with the two 120v lines.

Since the current from the CT sensors is what sense uses to determine what devices are being used, running Sense through a UPS in no way interferes with senses ability to detect devices even if it was running on UPS batteries. If on UPS batteries, watts used will be calculated based on what the UPS inverter is supplying for voltage so it may be a tiny bit off but it’ll be close enough.

Some other devices such as Smappee plug into 1 phase of 120V and calculate watts for both phases by multiplying the CT currents against that 1 phase only. Like I said, it’s not as accurate as one phase may show 118v and the other 121v, but again, it’s close enough.


Since I’ve had my sense, I’ve probably had a half dozen brownouts that I can recall. I know this because all of my networking and computer systems are on UPS devices so I can with certainty tell you that my Internet and Wifi access never went down. However, my sense did go offline and had to be hard cycled in order to restore service.

Not sure what else Sense needs to know in order to validate these orange boxes not resetting themselves when there are power fluctuations. If I’m here at home when the lights flicker, I can expect to see this message from my Fingbox show up in a matter of minutes…


It would be nice to get some input from a sense EE here to comment on the UPS situation. I suppose it wouldn’t much matter for these short interruptions we’re discussing here, but I still see longer outages as a problem (the separate UPSes will lose sync and then your 208v will drift down to 0) and I (perhaps mistakenly) think there is still some voltage regulation done in even the small consumer UPS units. My sub-$100 APC desktop PC UPS at home has an AVR.