A 22 kW standby generator, the most common size on the North Shore, burns about 2.2 therms of natural gas an hour. That is the half load most homes actually run during an outage. At current Nicor Gas and North Shore Gas rates, that works out to roughly $1.30 to $2.20 an hour. A full day of coverage runs about $30 to $60. A week-long outage lands somewhere between $220 and $400 in gas. That is far less than most homeowners expect once you see the math.
This guide breaks that math down by generator size, by utility, and by how many hours a day you actually run the unit. You will also see how those numbers compare to your furnace and stove. That way you know a generator will not strain your gas service.
How Much Natural Gas Does a Generator Burn Per Hour?
Quick answer: a standby generator burns more gas at full load than at half load. Load, not the size printed on the box, is what actually drives your bill. Most homes run their generator at roughly 30 to 50 percent of its rated output during a real outage, since not every appliance and circuit runs at once.
Every standby generator lists a natural gas consumption rate in cubic feet per hour. That rate changes with how hard the engine is working. The table below uses figures from generator manufacturer spec sheets and dealer consumption data. It covers the sizes most common in North Shore installs.
| Generator Size | Half Load (Typical Outage Use) | Full Load (Everything Running) |
|---|---|---|
| 14 kW | About 185 cubic feet per hour (1.8 to 1.9 therms) | About 250 cubic feet per hour (2.5 therms) |
| 22 kW | 221 cubic feet per hour (2.2 therms), per Generac's published spec sheet | Roughly 3 therms per hour under heavy load |
| 26 kW | About 215 to 260 cubic feet per hour (2.2 to 2.6 therms) | About 330 to 400 cubic feet per hour (3.3 to 4 therms) |
One therm equals about 100 cubic feet of natural gas, or 100,000 BTU. That conversion turns a cubic feet per hour number on a spec sheet into a dollar figure on your gas bill. If your home falls between these sizes, a 16 to 20 kW unit lands roughly between the 14 kW and 22 kW numbers above. Not sure which size fits your house? Our generator sizing guide breaks it down by square footage. Ask your installer for the exact figure on your model's spec sheet before you sign a contract.
What That Actually Costs on Nicor Gas and North Shore Gas
Quick answer: North Shore homes pay for natural gas in two parts. A supply charge covers the gas itself, and a distribution charge covers moving it through the pipes. Combined, Nicor Gas customers pay roughly 60 cents per therm before taxes and fees. North Shore Gas customers pay closer to 72 cents. Add taxes and the monthly customer charge, and most bills land closer to a dollar a therm.
As of August 2026, Nicor Gas' supply charge is 36 cents per therm. That is the price the utility is legally required to pass through with no markup. Layer on Nicor's distribution charge of about 24.4 cents per therm, reported by the Citizens Utility Board, and the combined rate lands around 60 cents per therm. North Shore Gas customers pay more on both sides. Their supply charge was 53.2 cents and their distribution charge was 18.7 cents as of early 2026, for a combined rate closer to 72 cents per therm. Both utilities also charge a flat monthly customer fee of about $21 to $22 regardless of usage. Gas prices change monthly for both utilities, so check the links above for the current number before you budget.
| 22 kW Generator | Nicor Gas (About 60¢/Therm) | North Shore Gas (About 72¢/Therm) |
|---|---|---|
| Per hour at half load | $1.30 to $2.20 | $1.60 to $2.40 |
| Per hour at full load | $1.80 to $3.00 | $2.15 to $3.30 |
| Full 24 hour day | $32 to $53 | $38 to $58 |
| Seven day outage, 24/7 | $224 to $371 | $266 to $406 |
The low end of each range is the commodity and delivery charge alone. The high end folds in taxes, riders, and your share of the flat customer fee. That is how most homeowners' actual bills read. Either way, a natural gas standby generator is cheap insurance. It costs far less than a spoiled freezer, a flooded basement, or a house with no heat in January.
Want a Firm Number for Your Home?
Fuel cost is only part of the picture. Tell us your address and home size and we will connect you with one local licensed and insured electrician who can size the right unit and quote the real installed cost.
Get a Free EstimateHow Many Hours Will Your Generator Actually Run?
Quick answer: a natural gas standby unit does not need to be rationed like a portable gas generator. It starts itself within seconds of an outage. It can run for as long as the gas line stays intact, day and night, without you refilling a tank.
That is the whole point of a natural gas standby system over a portable one. You are not choosing which hours to run it to stretch a five gallon can of gasoline. Most homes still see their real electrical load drop overnight. The AC, oven, and most lights sit idle while you sleep. That is why the half load figures above are the better planning number for a multi-day outage, rather than the full load numbers.
Short outages usually run the generator continuously until utility power returns. Longer events work differently. During the multi-day restoration after the July 2026 storms, homeowners saw their units cycle between lighter and heavier load throughout the day. The AC compressor or well pump would kick on, then off. That is exactly why the cost ranges above matter more than a single number.
Will a Generator Strain Your Gas Meter?
Quick answer: your installer checks this before the job is scheduled. They add up the gas load of your furnace, water heater, stove, and dryer. Then they confirm with Nicor Gas or North Shore Gas that your meter and service line can carry the extra draw from the generator.
A furnace alone can use more gas per hour than a standby generator running at half load. Most homes already have service sized to handle a large appliance. The utility, not your electrician, has the final say on whether your meter needs an upgrade before a generator gets tied in. Our natural gas versus propane guide covers meter capacity checks in more detail, including what to expect if an upgrade is needed.
Estimate Your Own Outage Fuel Cost
Quick answer: multiply your generator's therms per hour by your utility's price per therm. Then multiply by the hours you expect to run it. A 22 kW unit at half load on Nicor Gas for a 3 day outage lands around $95 to $160 in gas.
Here is the math in three steps.
- Step 1. Find your generator's therms per hour from the table above, or from your unit's spec sheet. Use the half load number for a realistic multi-day estimate.
- Step 2. Multiply that by your current Nicor Gas or North Shore Gas rate. Use 60 cents to a dollar per therm for Nicor, or 72 cents to a dollar-ten for North Shore Gas, unless you have a more current number from the links above.
- Step 3. Multiply by the number of hours you expect the outage to last. A 22 kW unit at half load on Nicor Gas running 72 hours straight comes to about $103. That is 2.2 therms times about 65 cents times 72 hours.
Compare that to a spoiled refrigerator and freezer. Compare it to a sump pump failure that floods a finished basement, or a hotel stay during a multi-day outage. Fuel cost is almost never the deciding factor in whether a generator makes sense.
Frequently Asked Questions
How much does it cost to run a whole house generator for a week?
For a 22 kW unit running continuously at half load on Nicor Gas, expect roughly $224 to $371 for a full seven days. The exact number depends on whether you are paying commodity charges alone or an all-in rate with taxes and fees. North Shore Gas customers should expect the higher end of that range, or slightly more.
Does a bigger generator always cost more to run per hour?
Usually, but load matters more than size. A 26 kW unit at half load can cost less per hour than a 22 kW unit running at full load. Fuel use tracks how much electricity the generator is actually producing, not just the number on the nameplate.
Is natural gas cheaper than propane to run a generator?
Yes, in almost every case. Our natural gas versus propane comparison breaks down the per hour cost of each fuel using current Illinois propane prices. Natural gas comes out well ahead for homes that already have gas service.
Will running my generator use so much gas that my furnace or stove stops working?
No. Your installer sizes the gas line and confirms meter capacity specifically so every appliance, including the generator, can draw gas at the same time without a pressure drop. This is a standard part of every North Shore installation.
Which costs more to run, Nicor Gas or North Shore Gas?
North Shore Gas customers pay a higher combined supply and distribution rate than Nicor Gas customers as of early 2026, roughly 72 cents per therm versus about 60 cents. Rates change monthly for both utilities, so check current pricing before budgeting a long outage.
Do I need to worry about running out of gas during a long outage?
Not the way you would with a portable generator's gas tank. A natural gas standby unit draws directly from the underground utility line. As long as the gas main to your neighborhood is intact, which is common even when the power grid is down, your generator can run for as long as the outage lasts.
Fuel cost should never be the reason a North Shore home skips a standby generator. Once you run the numbers, a multi-day outage costs less in natural gas than a single dinner out. It costs a lot less than the freezer full of food, the flooded basement, or the frozen pipes it prevents. Want a firm quote that includes both the full installation and what your specific home would cost to run? The form on this page connects you with one local licensed and insured electrician who can walk your gas service and give you real numbers.