Where is the best place to put a thermostat?
Put it on an interior wall at about eye level, in a room you use, where house air moves past it. Keep it away from supply registers, sunny windows, the kitchen, exterior doors, stairwells and outside walls. In a two-story or split-level, the main living level is usually right.
Key points
- Interior wall, about eye level, in a lived-in room with air moving past it.
- Outside walls, sunny windows, supply registers, kitchens and the bottom of a stairwell all fool the sensor.
- Cold air leaking out of the wire hole behind the thermostat is a common Minnesota problem and a quick fix.
- Test a suspect spot by taping a cheap thermometer beside the thermostat for a week.
- Remote room sensors can outvote a bad location when moving the wire is a big job.
The best place for a thermostat is an interior wall at about eye level, in the room where you spend your evenings, with house air moving past it and nothing nearby that heats or chills it. A thermostat only knows about the few inches of air around it. If that air runs warmer or colder than the rest of the house, the furnace and air conditioner chase the wrong number all season. Most "this room is always cold" and "the furnace never shuts off" complaints have more than one cause, but a thermostat in a bad spot is one of the cheapest to find and fix.
What makes a good thermostat location?
The right location has four things going for it:
- An interior wall. Not a wall with the outdoors on the other side of it.
- About eye level. High enough to miss the cool air along the floor, low enough to miss the warm layer at the ceiling.
- A room you use. Usually the main living area where you spend your evenings, not a guest room or an office that stays shut.
- Moving air. Out in the open where house air drifts past, not tucked behind a door, in a corner, or at the dead end of a hallway.
In a one-level rambler with a basement, the central hallway spot where a lot of these houses have it usually works fine, as long as bedroom doors stay open and there's a return grille nearby. In a two-story or split-level, the main living level is the default.
Which thermostat spots give false readings?
The same bad locations come up over and over:
- Outside walls. In January the wall surface runs colder than the room, so the thermostat reads low. The furnace keeps running and every other room overheats. This is worst in older Minneapolis and Saint Paul houses with little or no insulation behind the plaster.
- Near a supply register or in its airstream. Warm air hits the thermostat a minute after the burners light, it decides the house is done, and the furnace shuts off early. That shows up as short, frequent cycles, which our post on furnace short cycling covers.
- Direct sun. A thermostat that catches afternoon sun through a south or west window reads warm on a clear winter day. The furnace quits calling for heat right when the rest of the house is cooling off.
- The kitchen, or any wall with heat behind it. An oven, a dishwasher vent, a TV or lamp right below it, a fireplace, or a chimney or flue inside the wall all push the reading up.
- The bottom of a stairwell, or next to the front door. Cold air slides down stairs, and a split-level entry takes a blast of January air every time the door opens. The thermostat reads cold and overheats the upper levels.
- A bathroom wall. Steam and the heat from a long shower throw it off.
- A room that gets closed off. A thermostat in a bedroom or office with the door shut controls that one room and ignores the rest of the house.
The hole behind the thermostat
This one is a cold-climate special. The thermostat cable comes up through a hole from the basement, or sometimes down from the attic. In winter, warm air rising through the house pulls air through every wall cavity it can reach (the stack effect), and that hole lets cold air from inside the wall blow straight onto the sensor from behind.
The symptom is a thermostat that reads a degree or two colder than the room on windy, bitter nights and reads fine the rest of the time. The fix takes a few minutes. Turn the system off at the thermostat, pull the thermostat off its base, and plug the hole around the cable with a little non-hardening putty or a small wad of insulation. Then put it back. Don't pinch or nick the wires.
How do you test whether a thermostat is in a good spot?
You don't need special tools. Buy an inexpensive digital thermometer, tape it to the wall right beside the thermostat, and set a second one where you sit in the evening. Compare them a few times a day for a week: early morning, a sunny afternoon, while you're cooking dinner, and on a windy night.
- If the thermostat's display and the thermometer beside it disagree by the same amount every time, the sensor is simply off. Many digital and smart thermostats have a temperature offset setting that corrects a steady error.
- If the thermometer beside the thermostat and the one in your living room drift apart at certain times of day, the location is the problem. Sun, cooking and drafts cause swings an offset can't fix.
- If both thermometers agree but one room stays cold anyway, the thermostat isn't the cause. Look at airflow and ducts instead. Our guide to uneven home temperatures walks through the order we check.
Can one thermostat keep a two-story or split-level even?
A split-level or a two-story with a bonus room over the garage will have floors that run several degrees apart no matter where the thermostat goes. Heat rises, the upstairs takes the afternoon sun, and one duct system is trying to serve very different spaces. Moving the thermostat only changes which floor is comfortable.
Remote room sensors are the easier fix. Ecobee's Smart Thermostat Premium comes with a SmartSensor in the box, Google's Nest Learning Thermostat (4th gen) includes a Nest Temperature Sensor, and Honeywell Home and Sensi both sell room sensors for some of their models. You tell the thermostat which rooms matter and when, so a bedroom sensor can take over at night. Our guide to smart thermostats for Minnesota winters compares them. When the floors are far apart all the time, the real answer is a zoning system or duct work, not a smarter thermostat.
How hard is it to move a thermostat?
Relocating a thermostat means running a new cable from the furnace or air handler to the new spot and patching the old hole. Over an unfinished basement in a rambler, it's often a short job. Over a finished basement, in a two-story, or through plaster and lath, fishing the wire takes most of the time.
If you're moving it, run a cable with more conductors than you need today. Most smart thermostats want a C wire for steady power, and spare conductors cover a humidifier or a future heat pump. Our post on the thermostat C-wire explains why. When you're choosing between a relocation and remote sensors, weigh how bad the current spot is against how much wall you'd have to open.
Fix, sensors, relocation or zoning: what each costs
| Fix | When it fits | What it costs |
|---|---|---|
| Seal the hole behind the thermostat | Reads cold on windy nights | A few minutes and a little putty |
| Temperature offset | Off by the same amount all the time | Nothing; it's in the settings menu |
| Remote room sensors | Bad spot, but moving the wire means opening finished walls | The sensors, if your model supports them |
| Relocate the thermostat | Outside wall, sun, a register or the kitchen | Written price after we see the wall and the wire path |
| New smart thermostat, installed | Old unit can't use sensors or an offset | Typical national range $225–$400, per HomeGuide, plus $90–$135 if a C-wire has to be run |
| Zoning | Floors that run several degrees apart all the time | Typical national range $1,700–$3,500 for 2–3 zones in an existing home, per HomeGuide |
The HomeGuide figures are national ranges, not our prices. Ours come as a written, flat-rate quote before any work starts.
When it's the furnace, not the thermostat
Some symptoms look like a thermostat problem and aren't. If the furnace short-cycles no matter where the thermostat sits, the cause may be an overheating furnace tripping its limit switch, a dirty flame sensor or a furnace that's too big for the house. If the blower never stops, check whether the fan is set to On before blaming anything else; if it's on Auto and still running, a relay on the control board may be stuck. Those are furnace repair calls in Minneapolis and everywhere else we work. If the house has no heat at all on a cold night, start with our checklist for what to do when the heat goes out.
What to do next
Start with the thermometer test and seal the hole behind the thermostat. Both cost next to nothing. If the reading still wanders, or you want the thermostat moved or sensors added, our thermostat service covers relocations, new cable runs and setup. A service call for a thermostat or comfort problem carries a $79 trip charge, waived when you approve the repair, and you get a written, flat-rate price before any work. Call 612-429-3465, 7am–9pm, seven days a week.
Questions
How high should a thermostat be mounted?
About eye level for an adult, on an interior wall. That keeps it out of the cooler air along the floor and the warm layer near the ceiling. If someone in the house uses a wheelchair, mount it where they can reach it. If yours is already at a sensible height, don't move it for a few inches. What surrounds the thermostat matters far more than the exact height.
Should the thermostat be upstairs or downstairs?
With one furnace and one thermostat, put it on the main living level. A thermostat upstairs usually leaves the main floor and basement cold in winter, because the upstairs warms up first and shuts the furnace off. If the upper floor is always several degrees off, add remote room sensors or look at zoning and duct changes. No thermostat location can even out floors the ductwork doesn't serve evenly.
Can a smart thermostat fix a bad location?
Partly. A thermostat with remote room sensors can lean on a sensor in a better room, which helps when running new wire would mean opening finished walls. If the model lets you choose which sensors count, you can take the thermostat's own reading out of the average. Sun or drafts hitting the thermostat itself still make it a poor spot, so fix those where you can.
Can I move a thermostat myself?
Often, if you're comfortable fishing cable through walls. The wiring is low-voltage, but you'll be fishing a cable up from the furnace control board and filling the old hole in the wall. Turn the furnace off at its switch before touching any wires. If the old thermostat has thick wires joined with wire nuts, it's a line-voltage heater control, not a furnace thermostat, and it needs a different approach entirely.
Sources
- HomeGuide cost guides (2026 editions) homeguide.com