The short version: RTCOA’s CT-series thermostats predate most of today’s smart thermostat market and are largely out of production as a retail brand, but the CT50, CT80, and Z-Wave CT100 still turn up new-old-stock and secondhand, and they still have an unusually active hobbyist following because of a well-documented local API. If you want a modern app experience, look elsewhere. If you want a cheap, hackable thermostat for a Z-Wave or Home Assistant setup, this line still has a niche.

A note on sourcing: RTCOA is a legacy brand with no current professional review coverage or retail star-rating volume worth citing. What’s below draws on manufacturer/retailer spec listings, a couple of independent hobbyist blog write-ups (installation-focused, not consumer buying-guide style), and the existence of open-source tooling (a maintained Python client library for the local API) that points to a genuine, if small, long-running DIY community around these thermostats.

Who It’s For

DIY home automation users, particularly people running Home Assistant, OpenHAB, or a Z-Wave/Wi-Fi hub who want a thermostat with a documented local API rather than a cloud-dependent app. Not a fit for anyone who wants current software support, a polished mobile app, or manufacturer customer service — RTCOA’s retail presence has shrunk to secondhand and clearance stock, and some CT100 units were also rebadged and sold as the 3M/Filtrete 3M-50 in past years, so buyers should confirm exactly which hardware and firmware they’re getting.

The Lineup

  • CT30: Basic 7-day programmable thermostat, entry point of the line.
  • CT50: Wi-Fi model with a preinstalled USNAP Wi-Fi module, touchscreen, controls up to 2 stages of heat and 2 of cool. Wi-Fi only functions when the thermostat is C-wire/hardwired powered — running on batteries alone disables the network features.
  • CT80: Larger touchscreen, 3-stage heat/2-stage cool, and the standout feature for its era: it can monitor and control an external humidifier or dehumidifier based on humidity readings, not just temperature.
  • CT100: The Z-Wave-only member of the family, commonly bundled with DIY security systems and still one of the more recognizable “legacy” Z-Wave thermostats in home automation forums.

What Owners and the DIY Community Say

Independent hobbyist write-ups (rather than mainstream buying-guide reviews) describe the CT50 install and setup process as straightforward for anyone comfortable with basic thermostat wiring, with the app-based “learn when you’re away and adjust” feature being an early, if primitive, precursor to today’s geofencing. The CT80’s humidity control is called out specifically as a differentiator versus competitors in its era.

The strongest signal of real ongoing use is technical, not editorial: there’s a maintained open-source Python library (radiotherm) built specifically to talk to these thermostats’ local network API, which only exists because a nontrivial number of people are still running them inside home automation setups years after RTCOA stopped being a mainstream retail brand. That’s a meaningfully different kind of evidence than a star rating, but it’s real and verifiable.

We did not find current large-scale retail review data (Amazon, Best Buy, etc.) with enough volume to cite responsibly, and Consumer Reports’ listing for the CT50 sits behind a paywall we could not access.

Price & Value

Expect roughly $40-$100 USD depending on model and condition (new-old-stock vs. used). At the low end, this competes with modern budget Wi-Fi thermostats, but without current app support or manufacturer backing — you’re buying into a fixed feature set that won’t improve.

Pros & Cons

Pros:
– Documented local API, popular with Home Assistant/OpenHAB users
– CT80 offers humidity control, unusual at this price point historically
– Still findable cheap, new-old-stock or secondhand
– Works without depending on a company’s cloud servers staying online

Cons:
– Brand is effectively legacy/discontinued at retail; no meaningful ongoing manufacturer support
– App and firmware haven’t meaningfully evolved in years
– CT50’s Wi-Fi requires hardwired power, won’t work on battery alone
– No current professional review coverage or retail rating data to verify real-world reliability at scale
– Rebadged CT100 units (e.g., some Filtrete-branded units) create buyer confusion about exactly what you’re getting

The Recommendation

Buy an RTCOA CT-series unit only if you specifically want a cheap, locally-controllable thermostat for a DIY home automation project and understand you’re buying discontinued hardware with no forward software path. For anyone wanting a thermostat that’s actively supported and updated, a current budget model (Wyze Thermostat, Amazon Smart Thermostat, Honeywell Home T4 Pro) will serve you better for similar money.

Frequently Asked Questions

Is the Radio Thermostat Company of America (RTCOA) still in business?
The brand has largely disappeared from mainstream retail; these thermostats are sold now mostly as clearance, new-old-stock, or secondhand rather than through an active current product line.

Does the CT50 need a C-wire?
The CT50’s Wi-Fi function requires hardwired (C-wire) power. It can run on batteries, but network connectivity is disabled in that mode.

What’s the difference between the CT80 and CT100?
The CT80 is a Wi-Fi thermostat with humidity/humidifier control; the CT100 is the Z-Wave-only model in the lineup, more commonly used in DIY security and home automation setups rather than standalone Wi-Fi control.

Can I still get support if something goes wrong?
Don’t count on it. Given the brand’s reduced retail presence, plan on relying on DIY/home-automation community forums (Home Assistant Community, SmartThings Community) rather than manufacturer support.