Residential Appliance Usage Guide

Household appliances consume as much as 20% of the total energy used in your home, so it makes sense to use them wisely. To make more informed choices about how you use natural gas appliances and equipment, you first need to know how much energy your natural gas appliances or equipment are using.

To estimate how much it will cost you to operate a natural gas appliance or piece of equipment each month, you need to do three things:

  • Determine how many therms that appliance or piece of equipment uses each month.
  • Determine the cost per therm based on your rate. PSNC Energy has two residential rates, one for year-round customers and one for seasonal customers.
  • Calculate the natural gas usage and expense. (Remember, your calculations will be approximate.) 

Determine therm usage.
If you do not know how many therms the appliance or piece of equipment uses, there are a couple of ways to find out.

  • Locate the fuel rating plate attached to the appliance or piece of equipment. This will tell you its hourly BTU input as determined by the Underwriter's Laboratories (UL) and the American Gas Association (AGA). If you can’t locate the BTU rating plate or if the information is illegible, use the chart below. (Remember, these hourly and monthly therm usage estimates are based on PSNC Energy system-wide averages; the energy used by your specific appliance or piece of equipment may vary.)
  • Estimate the number of hours each month you operate that appliance or piece of equipment. It may be difficult to determine how many hours you operate a furnace or water heater because thermostats control them automatically. You may want to use the PSNC Energy Customer Natural Gas Appliance Usage chart below. 

Determine your cost per therm rate.
Your cost per therm rate can be found on your paper bill or on our website. Please make sure you are using the most current rate.

Calculate your natural gas appliance usage for each appliance or household equipment.

Use the following example to calculate the monthly therm usage for your appliance.


For Example:
 Suppose your gas logs have a 32,000 Btu hourly input rate, and that you burn your logs 3 hours a night for 15 days in the month. You can calculate the monthly therm usage as follows:

32,000 BTU x 45 hours = 1,440,000 Btu's per month.

1,440,000 Btu's per month
_____________________ =14.4 therms

100,000 Btu's per therm

14.4 therms x $1.18470* per therm = $17.06 estimated monthly cost of natural gas to operate your logs.

*Based on Gas - Residential Service from PSNC Energy as of June 1, 2007 not including monthly Basic Facilities Charge.

PSNC Energy Customer - Natural Gas Appliance Usage
These hourly and monthly therm usage estimates are based on system-wide average use by our residential customers.
Natural Gas Appliance or Equipment Estimated Monthly Energy Use Estimated Hourly Energy Use
Furnace* 100 therms
Vented Gas Logs
(3 hours per day,15 days per month)
29.25 therms .65 therms
Vent-Free Gas Logs
(3 hours per day,15 days per month)
18 therms .4 therms
Water Heater** 18 therms
Space Heater
(3 hours per day)
18 therms .2 therms
Grill .5 therms
Clothes Dryer 3.5 therms
Cook Top 2 therms
Remember the amount of energy used by your natural gas appliances and household equipment will vary based on the size and construction of your home, and the Btu input value and efficiency of the natural gas appliances or equipment you have.

*   Energy use for natural gas furnaces can vary for the same job depending on the efficiency of the equipment.

** Typical family of four usage.

  • Pre-1990, lower efficiency (less than 78% efficient)
  • Mid-efficiency (78% - 89% efficient)
  • High efficiency (90% efficient or better)
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