Use Your Thermostat to Save Big on Your Electric Bill This Summer

Do programmable thermostats save you money? Some believe that setting the thermostat higher while you're away wastes electricity by running the A/C harder to cool the house for your return. This article explains which is true and why, and shows how much electricity a programmable thermostat can save you with little discomfort.

What Happens to Electricity Usage with a Programmable Thermostat?

Heat flows from hot areas to cold at a rate governed by two things. Better thermal insulation between the areas slows heat flow, while greater temperature difference increases heat flow.

This article will concentrate on the latter factor - temperature difference. A higher thermostat setting while you're away raises interior temperature, decreasing the difference between indoors and out and reducing heat flow into your house.

Just before you return, the programmable thermostat lowers the setting and your house cools down. Since less heat flowed in, the A/C requires less electricity than it would have with a lower thermostat setting.

BGE Conducts Pilot Program to Reduce Critical Electricity Usage

BGE is the electric and gas utility serving much of central Maryland. In summer 2008 BGE started a pilot program to reduce electricity usage during critical times, giving program participants a $150 for participating. Two methods were tried - call them the "carrot" and the "stick."

The stick method reduces electric rate nearly in half during off-peak hours (85% of the time). Peak electric rates (13% of the time) are left unchanged. Critical period rates (2% of the time, 2 to 7 PM of 12 especially hot days) are punitive, at nearly 12 times higher than normal. BGE notifies participants the day before each critical period.

The carrot method uses a uniform rate, providing instead a credit of $1.75 for each kilowatt hour (kWh) saved during critical times. The electricity saved is calculated by comparing to average electricity usage during the previous 3 afternoons.

Personal Experience with the BGE Pilot Program

As participants in the "carrot" program, we set our thermostat lower than normal before critical periods to pre-cool the house. Then, we set our thermostat to 80 degrees just before 2 PM, and back to 72 degrees a few minutes after 7 PM.

From BGE reports we learned our summer usage from 2 to 7 PM is about 25 kWh. We also found the above thermostat exercise reduced our usage to 7 kWh during each critical period. Our experience shows several things.

First, A/C accounts for over 70% of our electricity usage on summer afternoons. Second, our temperature stayed under 75 degrees even on the hottest days. Third, setting our thermostat to 80 degrees from 2 to 7 PM in the summer should decrease our summer electric bill 20%.

Various estimates claim that setting your thermostat 1 degree higher in the summer reduces electricity usage 3-6%. Our experience shows an 8 degree higher thermostat setting reduced our electricity usage 72%, or 9% per degree, leaving our temperature under 75 degrees.

Setting the thermostat 1 degree lower in the winter is also said to save 3% of electricity usage. This winter we'll check our personal saving rate with a programmable thermostat.

Programmable Thermostats save Big Bucks on Electric Bills

Without discomfort, changing our thermostat setting saved us 72% during hot summer afternoons. Using a programmable thermostat year-round should reduce our electric bill 20%. Installing a programmable thermostat in your home and using it correctly can reduce your annual electric bill by hundreds of dollars.