Understanding your rate per therm is essential for managing natural gas costs in Northern Illinois. Your total rate combines two main components: Nicor's delivery charges and the gas supply charge. Together, these determine your effective cost per therm.
As of January 2026, typical total rates range from $0.70 to $0.85 per therm, depending on your usage level and the current gas supply charge. This guide breaks down how these rates work.
Delivery Charges
Nicor's delivery charges cover the cost of maintaining the pipeline network, reading meters, and providing customer service. These charges are regulated by the Illinois Commerce Commission and include:
- Monthly Customer Charge: Approximately $23.00 (fixed)
- Distribution Charge: Approximately $0.25-0.30 per therm
- Various surcharges: Infrastructure improvement, environmental, etc.
Delivery charges are relatively stable and change only when approved by the ICC through rate case proceedings.
Gas Supply Charge
The gas supply charge covers the actual cost of natural gas and fluctuates monthly. Recent rates include:
- January 2026: $0.42/therm
- December 2025: $0.39/therm
- January 2025: $0.28/therm
This charge typically represents 40-50% of your annual bill and is the primary source of month-to-month variation in your effective rate.
Calculating Your Effective Rate
To calculate your effective rate per therm, divide your total bill by your therm usage. For example, if your bill is $150 and you used 200 therms, your effective rate is $0.75/therm.
This effective rate will be higher than just the gas supply charge because it includes delivery charges and the fixed customer charge. The customer charge has a bigger impact on your effective rate when usage is low (summer months).
Comparing to Regional Rates
Nicor's rates are generally competitive with other Northern Illinois utilities. The Citizens Utility Board (CUB) tracks gas supply charges across Illinois utilities and can help you compare rates.
If your effective rate seems significantly higher than $0.85/therm (in winter) or $1.50/therm (in summer with low usage), it may be worth verifying your bill for accuracy.