11:24 am

Natural Gas 101 – DDDC Factor

In the ‘Natural Gas 101’ series here on ‘The Hot Spot’, we will be writing different posts to help educate you on various natural gas issues.

What is DDDC?

Have you ever looked at your natural gas bill and wondered how it all comes together? One line of your bill includes your DDDC which stands for Dedicated Design Day Capacity.  The DDDC Factor is a calculation done by Atlanta Gas Light Company (AGL) and is unique to each home or business. Basically, AGL is responsible for having enough pipe and storage capacity to meet every customer’s need during extreme cold weather conditions. For most residential customers and small businesses, natural gas is used for heat. And when it’s cold outside, you’ll want enough natural gas to keep your home or business warm. Your DDDC factor indicates how much natural gas deliverability is reserved (or ‘dedicated’) for your home or business if Atlanta were to reach an average daily temperature of 10oF (a ‘design day’).  You’ll see the DDDC Factor on your bill because it is used to calculate a customer’s AGL Pass-Through Charges.

Why did my DDDC change?

AGL recalculates and updates the DDDC at your location annually, so each September you will see an updated DDDC on your bill.  During this yearly calculation, AGL reviews the past gas consumption and usage pattern at your home or business. The most important influence on your DDDC calculation is how much gas was used last year during the coldest period of the year compared to your typical summer usage (if any).  A calculation is done to determine how sensitive your consumption is to cold weather and then used to set your DDDC indicating how much capacity should be reserved for your home or business.  Because your DDDC affects the AGL Pass-Through Charges, you may see a change in the amount of your bills year to year if your DDDC is adjusted.

Remember, your DDDC is tied to your location rather than you. So, if you move, your DDDC will be changed to the DDDC of your new location and then will be reset, as usual, in September.

For more information, visit Gas South’s Frequently Asked Questions or AGL’s Guide to Atlanta Gas Light Charges.

So, what do you want to learn about next?

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Lauren Tuten


Leave a Comment

  • Bill says:

    I have charges for a customer service fee, an AGL Pass Through Charge, and Taxes each month although I don’t have any gas consumption for the majority of the year in the summer months 0 CCFs.

    Is there some way to avoid these fees when I’m not consuming any product? I’ve looked into this before and I think there was a re-connect charge that amounted to more than just paying the fees and taxes?

    • Lauren Tuten says:

      Bill, thanks for the comment! There is a way that you can avoid paying the customer service fee, AGL Pass Through charges, and taxes throughout the warmer months. We call our customers that chose this option Seasonal Customers. You can turn your gas off in the spring and turn it back on in the fall, but there is a reconnect fee associated with the process. Depending on your account, you may find savings by going seasonal. We’ve sent an email to the address listed here and we’d love to take a look at your account for you to help you determine if this is the right option for you. Please reply to the email with your account number and we will call you to figure out how we can help. Thanks for reading Bill!

  • Chesley V. Morton says:

    So…if I happen to be on vacation next winter, during the coldest month, and use very little gas, my DDDC Factor will be lower for an entire year?

    • Lauren Tuten says:


      Thanks for reading and commenting with your question. You definitely have the right idea about how your natural gas use will affect your DDDC Factor. However, you never know when the coldest period of the year will be. For instance, this past March was unusually cold. Your DDDC Factor calculation also includes some additional factors that are not dependent on your individual natural gas use, but the entire Atlanta Gas Light system as a whole. We also hope, that for your sake, your DDDC Factor doesn’t determine when you take vacations :) . If you have any further questions, feel free to email us at social.media@gas-south.com. Thanks again, Chesley!

  • Jason says:

    I just reviewed my September bill and the Interstate Pipeline Charges increased from .973 DDDC to 16.209 DDDC! Yikes! Then the AGL pass through charge changed from $36.54 to $199.38. I used less gas last month and am paying $235 more. Is this correct? Can I have a representative explain this to me?

    Thank you in advance for your assistance.

    • Catherine Jennings says:

      Hi Jason, thanks for reading our blog! We are more than happy to look into your account, verify that everything is correct and talk through the charges with you. Please send me an email at social.media@gas-south.com with your name, phone number and account number. We will call you as soon as possible. Thank you.

  • Jeff Carpenter says:

    Why do I not have a DDDC rate on my bill? It just has a AGL #. Thanks!!

  • Catherine Jennings says:

    Thai, we have been getting a lot of spam comments lately and we apologize for that! We are working towards adding an anti-spam application to the comments section to fix this issue. Unfortunately, we do not have a way to remove you from receiving notifications. Hopefully the application will cut down on the notifications you receive. Thanks for following us.

  • Great delivery. Sound arguments. Keep up the great effort.

  • Patel says:

    What is the reason for ever month DDDC factor is different in gas bill. Thank’s for your time.

  • Buford says:

    My AGLC Base Charges are 56.88
    GNG Customer Service Charge is 4.99
    Gas Charge is 11.31
    Sales Tax is 4.45

    My Questions are

    1 – Why is my AGLC so High?
    2 – Why should I pay Sales Taxes on Service Charges. My Gas Usage was just 11.31.

    I am on Fixed income, I do not turn my Furnace on any more. My only Gas use is Stove and Hot Water Heater. My Water Bill is 8.00 per month, so I’m not using a lot of Hot Water.

    Given the Run around from my Gas Company.

    Please Help.

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