I'm going to say something that might ruffle some feathers: if you have a Honeywell thermostat and a propane heater, you should probably stop using the 'Auto' fan setting on your t-stat. I know. It sounds backwards. "Auto" is supposed to be the efficient option, right? That's what I thought too, for the first year I was managing our facility's HVAC budget.
I'm a procurement manager for a 12-person manufacturing company. I've managed our facility operations budget ($180,000 cumulatively across 6 years), negotiated with 40+ vendors, and tracked every invoice in our cost system. When I audited our 2023 spending, I found that our propane consumption was 17% higher than projected. I spent three weeks trying to figure out why. The culprit? A tiny setting on our Honeywell TH6110D1021 thermostats that I'd never second-guessed.
To be fair, I get why people use 'Auto.' It makes logical sense: the fan only runs when the system is heating or cooling. Less runtime = less electricity, right? Not always. It depends entirely on what you're heating with and how your space is configured. Here's where it gets interesting.
The Propane Heater Problem
If you're using a propane heater — and a lot of small manufacturing shops, warehouses, and garages do — the 'Auto' setting on your Honeywell thermostat can actually increase your fuel consumption. Here's the mechanism I discovered after digging into our data.
A propane heater works by warming the air in a localized area. When the thermostat hits the setpoint, the burner shuts off. In 'Auto' mode, the fan also shuts off. The problem is that heat stratifies. Warm air rises to the ceiling. The floor stays cold. The thermostat, usually mounted at eye level, senses the warm air at the ceiling and thinks the space is fine. Meanwhile, you're standing at a workbench with cold feet.
So what happens? You crank the thermostat up. The heater fires again. The fan blows hot air at the ceiling. The cycle repeats. You're paying to heat the ceiling, not the workspace.
In Q2 2024, I switched our seven shop thermostats from 'Auto' to 'On' — meaning the fan runs continuously. I expected our electric bill to go up. It did: about $28 per month. But our propane bill dropped by $140 per month. Net savings: $112/month. That's an 18% reduction in total heating cost. I've got the spreadsheet right here, dated June 2024.
Now, before you rush off to change your settings, let me add a caveat: this worked for us because of our specific context. We have high ceilings (14 feet), concrete floors, and we're a metal fabrication shop with constant bay door openings. If you're in a well-insulated office with 8-foot ceilings, the calculus might be different. You might not see the same savings.
The Honeywell TH6110D1021: A Workhorse That Needs a Tune-Up
I'll be honest: I didn't expect to become a Honeywell thermostat evangelist. But after comparing 8 thermostat models over 3 months using our TCO spreadsheet, the TH6110D1021 won for our application. It's not the cheapest upfront ($42 vs. $29 for a basic model), but it has one feature that saves us money: an adjustable fan cycle rate.
Most people never touch this setting. The default is typically 3 cycles per hour (CPH). For a propane heater, I recommend dropping it to 1 or 2 CPH. Here's why. Every time the system cycles on, there's a purge period where the fan blows cold air through the ducts before the heat exchanger warms up. With a propane system, that cold air blast actually makes the thermostat think the room is cooler than it is, triggering another cycle. You get short-cycling, which eats fuel.
On the Honeywell, you access this by holding down the 'Menu' button for 5 seconds, navigating to 'Installation Settings,' then 'System Settings,' then 'CPH.' I had to call Honeywell support to figure this out (note to self: actually read the manual next time). Setting it to 1 CPH reduced our on/off cycles by about 60%. The room temperature fluctuates a bit more — maybe 3 degrees instead of 1 — but the propane savings more than justify the slight comfort trade-off.
I should note: this is specifically for propane heaters. If you're using a heat pump, the ideal CPH is different (probably 2-3). If you're using electric resistance heat, it matters less. Your mileage really will vary. I can only speak to propane because that's what we use.
The Ryobi Fan Situation: When More Airflow Is Actually Worse
Here's where it gets counter-intuitive. We use a lot of Ryobi fans in our shop — the big 18-volt ones on stands. They're great for circulating air in summer. But in winter? I almost made a costly mistake.
In November 2023, I bought six Ryobi fans ($79 each) for the summer and left them set up. When winter came, someone turned them on to help distribute heat. The logic: if the warm air is at the ceiling, blowing it down will even out the temperature. Sounds smart. It wasn't.
The problem is that ceiling-mounted fans (or fans blowing upward from the floor) do a great job of destratifying air. But a floor-standing Ryobi fan pointed horizontally? It creates a wind chill effect. The air moving across your skin makes you feel 5-10 degrees colder. So people cranked the thermostat. Propane consumption went up again.
I realized this after tracking two weeks of data. The week with the fans running, we used 43 gallons of propane. The week without, 31 gallons. That's a 38% increase. The fans were making us colder, so the heater ran more.
The solution was simple: we installed ceiling fans (big, industrial ones) that push air down without creating a breeze at floor level. Cost: $450 each, installed. We bought four for the main shop area. Initial outlay: $1,800. First winter savings on propane: $720. Payback period: 2.5 years. That's a solid ROI by our procurement standards.
Now, I'm not saying Ryobi fans are bad. We still use them in summer for spot cooling at individual workstations. They're great for that. But using them in winter with a propane heater? I'd recommend against it.
How to Reset Your Honeywell Home Thermostat Without Losing Your Mind
Since I've been talking about changing settings, let me address the elephant in the room: resetting a Honeywell thermostat can be a pain. The TH6110D1021 is generally user-friendly, but if you need a full factory reset, here's the sequence that actually works (confirmed on our units, firmware version 04.01, as of September 2024):
- Press and hold the 'Menu' button for 5 seconds
- Scroll to 'Preferences'
- Scroll to 'Restore Defaults'
- Press 'Select'
- Confirm with 'Yes'
That'll wipe everything, including your schedule and temperature offsets. Warning: your fan settings (CPH, cycle rates) will also reset to factory defaults. So if you changed those like I recommended, you'll need to set them again.
I learned this the hard way. I reset a thermostat thinking I was just clearing the schedule, and suddenly my carefully tuned CPH settings were gone. Spent another hour on the phone with support. Not my finest procurement moment.
The 'Can Fan' Alternative: A Surprising Solution
One more thing about airflow. A lot of people in our industry ask about 'can fans' — the inline duct fans used for ventilation. We tried using one to destratify air this year. I bought an 8-inch can fan ($67 on Amazon, December 2024 pricing) and mounted it in the ceiling, venting warm air down through a flexible duct.
Results? Mixed. It worked for localized destratification — the area directly below the fan was noticeably warmer. But it was noisy (52 dB at full speed) and created a noticeable draft. The Ryobi fan issue all over again, but from above.
If you have a small workshop or a single bay, a can fan might be a good option. But for our 4,000-square-foot shop, the ceiling fans were a better investment. I'd recommend a can fan for a garage or single work bay; stick with ceiling fans for larger spaces.
This pricing was accurate as of December 2024. HVAC equipment prices change fast, so verify current rates before budgeting.
The Bottom Line: Not Every Setting Is Optimal for Every Fuel
I know I've thrown a lot at you. Let me summarize my argument clearly:
'Auto' fan mode on a Honeywell thermostat is not the enemy. It's a great setting for central air conditioning in a well-sealed house. But if you're using a propane heater in a workshop or warehouse setting, running the fan continuously (or at least adjusting your CPH settings) will likely save you money on fuel — even if it costs a bit more in electricity.
I've been managing our facility budget for 6 years. I've tested both approaches, tracked the data, and the numbers are clear for our context. Your context might be different. If you have a tight, modern building with good insulation and a heat pump, my advice doesn't apply. If you're in a drafty shop with a propane heater and a basic Honeywell thermostat, it probably does.
I get that some people will disagree. I've seen forum posts where HVAC techs insist 'Auto' is always better. I think those people haven't run the numbers on propane consumption with actual meter readings. Talk to me after you've tracked 6 years of invoices and seen the patterns.
At the end of the day, I don't care which brand of thermostat or heater you use. What I care about is that your settings match your actual situation. Don't trust a default setting. Question it. Test it. Measure it. Your budget (and your propane bill) will thank you.
