What Are Thermostat Ghost Readings?

Ghost thermostat readings aren't supernatural, but they can suck the life out of your energy budget. Here is what they are and how to avoid them.

Your home’s thermostat works by monitoring the temperature and using that information to regulate when your furnace or air conditioner turns on. That’s great in theory, but note that it only takes account of the temperature immediately surrounding the thermostat. If that area is warmer or colder than the rest of your home, you’ll struggle with uneven temperatures and unnecessarily high utility bills throughout the year.

These seemingly illogical temperatures are often called “ghost readings” because they seem to reflect an entirely different reality. If you want to keep your home comfortable, it’s time to bust those ghosts and troubleshoot a non-functioning thermostat.

Simple Causes and Fixes

Common causes for ghost readings include a thermostat exposed to prolonged direct sunlight, a draft source such as a door or window, or a source of heat such as a kitchen or fireplace. Another is a thermostat that’s been placed on an exterior wall, allowing the thermostat to be influenced by the temperature outside.

A thermostat located on a wall next to duct work or a hot water line presents another potential problem. In both cases, when that utility is used, it will cause a temperature swing that can be detected by the thermostat.

The simplest fix is to move your thermostat to a better location. Look for an interior wall away from sources of heat and cold, protected from direct sunlight. This will usually require fishing a low voltage line from the furnace to the thermostat, but it’s a relatively easy DIY project. Adjusting your thermostat may save you money.

A More Involved Fix

A slightly more complicated cause of ghost readings is a home whose size or layout makes effective distribution of your treated air difficult. This is often most noticeable in multistory homes where the thermostat is located on the first floor. The temperature difference on other floors can be as much as 10 degrees.

Solutions include a zoned HVAC system or multi-split unit, but there’s also a simpler option. Multi-room temperature sensors are designed to be placed throughout the house, usually connected by a wireless network. With these multiple readings, your thermostat can find a “Goldilocks” balance between the various parts of your home and make the temperature just right.

Some thermostats are even smart enough to use the living areas as their benchmarks during the day and bedrooms at night. After all, what matters most is the comfort level of the areas you use the most. The most comfortable temperature changes with the seasons, such as the best temperature for a house in winter.

High-Tech Ghost Busting

It’s no surprise that there have been significant advances in smart thermostats and wireless connectivity in the past few years. Many smart thermostats can be controlled via smartphone apps, and they can use your phone’s location to track your movements throughout a home. They can even shut down when you’re more than a certain distance from your home, then turn back on when you return.

Another option: Motion sensors that track the movements of you and your family. That allows the HVAC system to heat or cool according to where you’re spending your time.

Whether you decide to relocate the thermostat or invest in new technology, eliminating ghost readings and streamlining the efficiency of your HVAC system can cut your energy costs.

Luke Miller
Luke Miller is an award-winning garden editor with 25 years' experience in horticultural communications, including editing a national magazine and creating print and online gardening content for a national retailer. He grew up across the street from a park arboretum and has a lifelong passion for gardening in general and trees in particular. In addition to his journalism degree, he has studied horticulture and is a Master Gardener.