Nicor Gas Winter Bill Spike

Winter gas bills in Northern Illinois can be 5-10 times higher than summer bills, shocking many homeowners when January and February bills arrive. Understanding why this happens—and what's normal—helps you plan for seasonal cost increases and identify when something might be wrong.

The primary driver is heating demand. While summer gas usage might be 15-25 therms (water heating, cooking, dryer), winter heating in Northern Illinois can push usage to 200-350+ therms per month during the coldest periods.

Northern Illinois has one of the longest and coldest heating seasons in the country. Heating is typically needed from October through April, with December through February seeing the highest usage.

A typical Northern Illinois home might use:

• Summer (June-August): 15-25 therms/month
• Shoulder (April-May, Sept-Oct): 40-80 therms/month
• Winter (Nov-March): 150-350+ therms/month

Homes with poor insulation or older furnaces may see even higher winter usage.

Heating costs are directly tied to outdoor temperature. Utility bills often reference "heating degree days" (HDD)—a measure of how cold it was during the billing period.

A billing period with 1,200 HDD will result in roughly double the heating usage of a period with 600 HDD. This is why bills can vary significantly between winters—a mild January might cost $150 while a brutal one costs $300+.

Winter bills are often higher than expected because multiple factors compound:

• Higher usage: 10-15x more therms than summer
• Higher supply rates: Gas supply charges often peak in winter
• Longer billing periods: Some winter bills cover 32-35 days

The combination of these factors can result in bills that are 8-12x higher than summer months.