FilterWatch FAQS

FW actual image

What exactly is FilterWatch ?

When you install a new filter in your system, the air flows across the filter at a high speed. The exact speed is different for everybody. As the filter gets dirtier and dirtier, that initial speed gets lower and lower. FilterWatch constantly measures that speed and alarms when that speed is 25% less than the initial speed. Its a AAA battery powered sensor with a lot of smarts.

How is FilterWatch installed?

As you can see in the image, FilterWatch attaches to the rim of the return vent or in some cases to the rim of the register in a room. We use 2-sided VHB tape from 3M. Just peel the protective cover and press in place. (note: ‘register’ is used for air exit point is a room, and ‘vent’ is used for cover of filter at the return point).

FW on vent

Return Vent


Room Register



My HEPA filters cost $10-$15 and that’s why I don’t change them but every 45 days or so. What if my filter is 25% clogged after 20 days?

The amount of money FilterWatch can save you depends on several factors including, energy costs in your area, total run time during a typical day in you peak season, and finally the cost of the filter. Our goal isn’t to match what you do today, our goal is to save you money. Think of it this way, of the extra energy you are wasting because of a clogged filter, 85% or more will occur during the 4-6 month peak season. If you normally change your filter 6 times a year, 5 of those times should be in the 4-6 months of your peak season! FilterWatch does this naturally because the more your system runs, the faster the filter will clog. You don’t have to think about it, FilterWatch will do that for you.

If you are still a little nervous about changing a filter too soon, then you can just reset the alarm and do nothing. FilterWatch will add 10% to the clog percent target and alarm you when that is reached. We do this up to 45% (2 resets) and at that point we will continuously alarm until the filter is changed. It will stay at 45% until you turn the power off and back on so use this sparingly.

I never seem to have filters when I am ready to make a change, what happens if the alarm goes off and I don’t have a filter ready?

In our Basic low cost model, we give you 3 days before we actually check to see if the filter was changed. Its up to you to remember, otherwise, we will add 10% and alarm when the filter is 35% clogged. If you decide to change the filter after that time, you will need to reset FilterWtach but turning the unit off and back on.

We currently have a wireless model that connects to some popular smart home hubs and in the near future we will have a Bluetooth version that will send notifications to your phone. Finally, at some point we will be able to send you a filter at about the cost you can pick one up at Home Depot.

Adding wireless also adds some significant capabilities that we believe will benefit homeowners with A/C systems. That is about 80 million homes in the US and 50 million of those are heavy users. 2 FilterWatch able to communicate with each other and connected to the internet, we will be able to determine if an A/C system is low on refrigerant. Low refrigerant is also a large contributor to WASTED energy in households with A/C.

How long will the batteries last?

We targeted 1 year before the batteries will need replacing. We will alarm you when that occurs. It turns out that the batteries will last 18 months on average and future models bump that up to almost 3 years!

What is the LCD display for?

The model show above was our first version. It has a host of sensors including humidity, pressure, vibration, light, temperature, and of course airspeed. It also has 3 wireless technologies including WiFi, Bluetooth Smart, and ZigBee. We provided these to our crowd fund supporters and we use them as engineering development tools. What we learn with these may end up in lower costing units target with specific sensors.