Honeywell Home New! Honeywell Home Programmable Thermostat, Single-Stage, 1 Heat/1 Cool Compatibility, 5-2 Day Schedule, X2P, White, RTH20B

Why I chose this thermostat

I needed a simple, reliable programmable thermostat for a single-stage system in a space that doesn’t have a C-wire. I wasn’t looking for Wi‑Fi, app control, or smart-home tie-ins—just a clear screen, dependable temperature control, and a schedule that would save energy without fuss. The RTH20B fit that brief on paper: 1 heat/1 cool compatibility, 5‑2 day scheduling, battery power, and an easy wall plate. After living with it, I’m glad I went with the simpler option.

Installation and setup

Installation was straightforward thanks to the UWP wall plate. The plate has spring-loaded terminals and generous wire labeling, which made moving the existing wires over quick. If you’re replacing another Honeywell with a UWP plate, the swap is even faster. I leveled the plate, snapped the base on, and that was that.

Because this model runs on two AA batteries, it doesn’t require a C‑wire. That’s a big win if your old thermostat only had two or three conductors available. I just installed batteries, mounted the body to the base, and powered on.

Initial setup uses a series of numbered configuration options—things like system type and fan operation behavior. It’s sensible once you understand the logic, but it isn’t a tap-and-go wizard. Keep the manual nearby the first time; the numbering makes sense after a minute, and you only do this once unless you change systems.

A couple of practical installation notes:
- Label your old wires before removing them; “R” and “Rc” are treated correctly by the base, so you don’t need a jumper.
- Double-check you truly have a conventional single-stage system. This model is not intended for electric baseboard (120–240V) and isn’t the right choice for multi-stage or heat pump systems.
- If your system is a 750 mV millivolt heater (older wall furnaces or some fireplaces), this unit supports that, which is increasingly rare at this price.

Design and usability

The display is large, legible, and backlit. I could read the current temperature from across the room, and the backlight is bright enough without being harsh. The fonts are clear and the layout is uncluttered. You can tweak some display preferences in the settings to suit your space, which I appreciated in a hallway with variable light.

Controls are old-school in the best way: physical buttons instead of a touchscreen. That makes it easy to operate with cold hands, and it also means no accidental taps. There are dedicated buttons for temperature up/down and navigating the menu, so basic changes are quick.

I prefer the physical “system” and “fan” controls over buried digital toggles. The fan can be set to Auto or On, and switching modes between Heat, Cool, or Off is immediate.

Scheduling and everyday use

Programming is 5‑2, so weekdays have one schedule and weekends another. Each day block has four periods that line up with typical routines—Wake, Leave, Return, Sleep—each with its own time and temperature. That’s enough to capture the energy-saving basics without micromanaging.

Entering the schedule using buttons takes a few minutes, and I recommend writing down your target times and temps before you start. Once set, it’s mostly “set and forget.” For ad hoc changes, temporary holds work the way they should: tap the arrows, and the thermostat maintains that temp until the next programmed period. Permanent holds are available if you want to pause the schedule entirely, and there’s also a non‑programmable mode if you prefer to control temperature manually all the time.

One thoughtful touch is the change filter reminder. You can choose how you want it to track (time-based or run-time-based, depending on your preference), and it’s easy to reset when you replace the filter. It’s a quality-of-life feature that helps keep systems efficient.

Performance and temperature control

In daily use, the thermostat held setpoints consistently. I measured room temperature with a separate thermometer and found readings aligned within about a degree Fahrenheit—well within what I expect for a non-connected, battery-powered unit.

Cycle behavior was smooth with my single-stage gas furnace and central air. The thermostat didn’t short-cycle or overshoot in a way that would be noticeable, and the transitions between periods in the schedule felt natural. Fan behavior was predictable, and switching modes never produced any surprises.

If you notice the system running unexpectedly after installation, in my experience it’s worth re-checking two things: that the wiring matches your system type and that the configuration menu is set correctly for 1 Heat/1 Cool conventional. A misconfiguration can cause odd behaviors that look like hardware issues but aren’t.

Compatibility limitations to consider

This model is designed for:
- Single-stage heating and cooling (1 Heat/1 Cool)
- Conventional forced-air systems (gas, oil, or electric furnace/air handler)
- Hot water systems
- 750 mV millivolt systems

It is not compatible with:
- Electric baseboard heat (120–240V)
- Multi-stage or heat pump systems

If you have a heat pump or you’re planning to upgrade to a multi-stage system, look elsewhere. Likewise, if you need remote control or smart-home integrations, this isn’t the product category you want.

Power, maintenance, and the low-heat floor

The thermostat runs on two AA batteries. That’s the main reason it’s so flexible in homes without a C‑wire. In practice, battery changes are quick, and because the body lifts off the base, swapping cells doesn’t disturb the wiring. I prefer AA over smaller cells; they’re cheap, easy to find, and have predictable life.

The extended low-heat setpoint down to 32°F is a useful niche feature. If you’re protecting a garage, workshop, or a vacation property from freezing without heating it to room temperature, this lets you keep the thermostat at a frost-protection level. Not every budget programmable unit offers that.

Between the battery power, filter reminders, and straightforward controls, ongoing maintenance is minimal.

What I’d improve

No product is perfect. Here’s what could be better:
- Setup flow: The numeric configuration menu works, but a guided on-screen wizard would be friendlier for first-time installers.
- Scheduling speed: Entering all four periods for two day blocks is a little tedious via buttons. It’s not hard, just time-consuming.
- Feature scope: No Wi‑Fi or app control, by design. That’s fine for my use, but it’s worth underscoring for anyone expecting remote access.
- Warranty: A 1‑year warranty is standard, though I’d love to see two years as a sign of confidence.

Who it’s for

• Homes with single-stage conventional systems that lack a C‑wire
• People who want simple 5‑2 scheduling and a big, readable display
• Landlords or property managers seeking dependable, non-connected thermostats
• Garages, workshops, or seasonal spaces where the 32°F setpoint is valuable
• Owners of older millivolt systems who need compatible control

Who should skip it:
- Anyone with electric baseboard, multi-stage, or heat pump systems
- Users who want smart-home control, voice assistants, or app scheduling

The bottom line

The RTH20B is a practical, no-drama thermostat that prioritizes clarity and reliability over connectivity. Its easy installation, large backlit display, 5‑2 scheduling, and battery power make it well-suited to older homes, rental units, and any location where a C‑wire isn’t available. Temperature control was steady in my setup, and the change-filter reminder plus the 32°F low-heat option add real-world utility.

Recommendation: I recommend this thermostat for single-stage households that want a straightforward, non‑Wi‑Fi programmable unit—especially where a C‑wire is absent. It’s easy to install, easy to read, and once programmed, it quietly does its job. If you need advanced features like app control, multi-stage support, or heat pump compatibility, this isn’t a fit. For everyone else, it’s a solid, budget-friendly choice that gets the fundamentals right.