You set the thermostat for 68 degrees at 7 AM, but you wake up shivering because it never actually reached that temperature. Or you programmed a schedule last winter, and somehow the house is still blasting heat at noon when everyone is at work. Programmable heating systems promise convenience and lower bills, but the reality is messier than the marketing lets on.
This article covers the seven disadvantages that manufacturers don’t talk about. Not the obvious stuff like ‘you have to remember to set it.’ I mean real, technical, and behavioral downsides that can leave you colder, paying more, or replacing the thermostat sooner than expected. You’ll also learn which problems a solid basic model like the Honeywell Home RTH20B solves, and which ones it doesn’t.
Honeywell Home
New! Honeywell Home Programmable Thermostat, Single-Stage, 1…
CUSTOMIZE: Choose to receive change air filter reminders and select display settings to optimize this thermostat for home.The RTH20B is a direct replacement for the RTH2300, and replacement for the RTH221 offering 5-2 scheduling
See on AmazonThe Honeywell Home RTH20B is a simple single-stage, 1-heat 1-cool programmable thermostat with a 5-2 day schedule. It has a large backlit display and a change-filter reminder. It won’t do zone control or learn your habits, but for a basic replacement it avoids a lot of the complexity that causes the hidden disadvantages below.
The ‘Set It and Forget It’ Myth — Why Programmable Thermostats Don’t Always Save Money
The biggest lie in the HVAC world is that programming a setback schedule automatically cuts your bill. It does not. The savings depend entirely on how long your house can hold heat without the furnace turning back on too early.
Most programmable thermostats use a fixed start time for recovery. Say you set 62°F at night and want 68°F by 7 AM. The thermostat starts recovery at 6 AM, right? But if your house loses heat fast, the furnace might run continuously for an hour, using more energy than if you had kept a steady 65°F all night. Short setbacks — less than 4 hours — often waste energy because the recovery overshoots and cycles inefficiently.
And here’s the kicker: many people set one schedule and never touch it, but their daily routine changes. So the house heats up empty rooms for hours. A study from the Department of Energy (DOE) years ago showed that manual adjustment by a diligent user actually saved more than a poorly programmed thermostat. The Honeywell RTH20B at least lets you choose a non-programmable mode if you prefer manual control, which is a smart fallback.
The ‘Easy to Program’ Myth — Why Most People Never Program Their Thermostat
Walk into any hardware store and you’ll see rows of programmable thermostats with ‘easy programming’ written on the box. The reality? Studies show that nearly 60% of homeowners never program their programmable thermostat at all. They leave it on hold, defeat the schedule, or just tap the up and down buttons because the interface is too confusing.
The problem is tiny buttons, cryptic menus, and manuals that read like legal documents. The Honeywell RTH20B improves on this with a large screen and clear font, plus a 5-2 day schedule that’s straightforward. But even then, you need to learn the sequence: press Set, then use arrows, then select day groupings, then set times. Miss one step and you accidentally set the whole week to 82°F.
This isn’t laziness. It’s bad design. Manufacturers assume people will read the manual, but they won’t. So the hidden disadvantage is that the thermostat becomes a glorified manual dial — all the complexity, none of the savings.
Three Hidden Technical Disadvantages That Catch Homeowners Off Guard
Let’s move past user behavior and into hardware and system compatibility. These three issues can ruin your heating season no matter how well you program the thing.
1. Battery dependence and schedule loss during power outages. Most basic programmable thermostats run on AA batteries. When the batteries die, the schedule resets to factory default. A 10-second power flicker does the same thing if the thermostat relies on house power for memory. You come home to a cold house and a blinking clock. The Honeywell RTH20B holds its schedule with batteries, but you still have to replace them yearly. If you forget, it’s back to square one.
2. Incompatibility with heat pumps and multi-stage systems. A single-stage thermostat like the RTH20B only works with one heating and one cooling stage. If you have a heat pump with auxiliary heat, or a two-stage furnace, this thermostat cannot control them properly. You’ll either get no heat or short cycling that damages the compressor. Always check your system type before buying.
3. Inaccurate temperature sensor placement. The thermostat reads the temperature at its own location, usually in a hallway. If that spot is drafty or near a heat source, the whole house suffers. Programmable thermostats can’t adjust for that; they just follow their sensor. Remote sensors exist for some models, but the RTH20B has no remote sensor option. You must mount it wisely.
Over-Programming and the ‘Zoning’ Blind Spot
Most homes have a single thermostat for the whole house. You can program it to 68°F during the day, but the upstairs bedroom might be 72°F while the basement is 62°F. A programmable thermostat does not solve uneven temperatures; it only controls one zone.
Homeowners often try to compensate by cranking the temperature up or down, which makes the imbalance worse. The real fix is zoning — separate thermostats for different parts of the house — but that’s expensive and not what a basic programmable unit offers.
If you live in a single-story open floor plan, you’re fine. But if you have multiple levels or rooms with different sun exposure, a single programmable thermostat can actually increase discomfort. You’ll find yourself overriding the schedule constantly, which defeats the purpose.
| Approach | How It Works | Pros | Cons |
|---|---|---|---|
| 5-2 day schedule (like RTH20B) | Same program for weekdays, separate for weekends | Simple, fewer steps to set | Can’t vary Tuesday vs Thursday |
| 7-day schedule | Different schedule for each day | Maximum flexibility | Takes forever to program, easy to mess up |
| Smart learning thermostat | Learns your habits and adjusts automatically | No manual programming needed | Expensive, may not learn accurately, requires Wi-Fi |
| Manual override (non-programmable mode) | You adjust temperature by hand when you need it | Full control, no learning curve | Requires discipline, easy to forget |
As the table shows, each approach has a trade-off. The 5-2 schedule is a good middle ground for people with predictable weekday routines. The Honeywell RTH20B’s 5-2 option is one of the simplest to set, but you still need to commit to it.
Frequently Asked Questions
Do programmable thermostats really save money?
They can, but only if you set a proper setback of at least 8 hours per day and your home doesn’t lose heat too fast. Typical savings range from 5% to 15% on heating bills according to the DOE, but those numbers assume correct usage. Many people see zero savings because they never program it or use too-short setbacks.
Will a programmable thermostat work with my old furnace?
It depends. Most modern programmable thermostats work with standard 24-volt gas, oil, or electric furnaces. But if your system is older (millivolt or line voltage), you need a compatible model. Also check whether your furnace uses a common wire (C-wire) for power; some thermostats need it. The RTH20B is battery-powered, so no C-wire required.
Why does my programmable thermostat ignore the schedule?
Usually because the ‘hold’ feature is active. Many thermostats stay on hold indefinitely until you manually cancel it. Also, some models have a temporary override that lasts a few hours, then resume — but if you set the temperature manually before the program kicked in, it overrides. Read your manual for ‘run schedule’ button.
Is a 5-2 day schedule good enough?
For most people with a consistent work-week and weekend routine, yes. You lose the ability to differentiate Monday from Wednesday, but that’s rarely necessary. If your schedule varies wildly, a 7-day or smart thermostat makes more sense. The Honeywell RTH20B’s 5-2 schedule is a solid choice if you commute to a 9-to-5 job.
Can a programmable thermostat damage my HVAC system?
Rarely, but yes. If the thermostat forces the system to cycle on and off too frequently (short cycling), it can wear out the compressor or blower motor. This happens with incompatible thermostats or when the temperature differential is set too narrow. Most thermostats have a built-in time delay to prevent that, but cheap models may not. The RTH20B has a standard 5-minute compressor protection.
What You Should Do Before Buying a Programmable Thermostat
Programmable heating systems are not a magic bullet. They work well when matched to your lifestyle and equipment. Before you buy one, consider these points.
- Check your HVAC system type and stage count. A single-stage thermostat like the Honeywell RTH20B only handles one heat and one cool. Multi-stage or heat pump systems need a different model.
- Decide if you will actually program it. If you’re not willing to spend 20 minutes setting the schedule, buy a manual thermostat instead. The RTH20B has a non-programmable mode, which is an honest option.
- Place the thermostat on an interior wall away from drafts, direct sun, and heat sources. Bad placement ruins any schedule.
- Replace batteries once a year. Set a calendar reminder. A dead battery wipes your schedule and leaves you freezing or roasting.
- Consider a smart thermostat if you need zoning or remote control. But for a simple, reliable replacement, the RTH20B’s 5-2 schedule and large display make it a practical choice — energy efficiency depends on usage, not just the hardware.
- Read the manual before installation. It saves hours of frustration. Most complaints about programmable thermostats come from skipped instructions.
- Understand that no thermostat can fix an under-sized or poorly insulated home. Insulation and duct sealing are the real advantages of programmable systems only after the building itself is efficient.
