Generac Generator Running Costs Per Hour: Fuel Consumption and Operating Expenses

Power outages around Charlotte tend to arrive on a humid August afternoon or during a winter ice glaze that snaps lines along Providence Road. The first hour without power is inconvenient. By hour three, the fridge is warming, the sump pump is off, and the home office goes dark. That’s when homeowners who invested in a Generac standby generator breathe a little easier. Still, the same question comes up every time we size, install, or service a system: what does it actually cost to run a Generac generator per hour?

This guide gives you clear numbers, real examples, and local context for Mecklenburg County homes. You’ll see how fuel type, generator size, and load affect the dollar figure on your next outage. If you’re searching “Generac generator service near me,” you’ll also find practical advice on tuning, service intervals, and load management to keep operating costs in check.

The two big drivers: fuel and load

Operating cost is primarily fuel. Everything else is secondary. Generators convert fuel into electricity, and the rate depends on the generator’s size (kW rating), fuel type (natural gas or propane for most Charlotte homes), and how hard the unit is working (percentage of load).

A typical residential standby generator runs on:

• Natural gas (NG): measured in cubic feet per hour and billed in therms by your utility.
• Liquid propane (LP): measured in gallons per hour.

Diesel models exist, but most Charlotte-area homes with automatic standby power use air-cooled natural gas or propane Generac units in the 10 to 26 kW range. Air-cooled units are dominant for single-family homes in neighborhoods like Ballantyne, Dilworth, SouthPark, and Huntersville.

Load is the other lever. A 22 kW unit at 30 percent load drinks a different amount of fuel than the same unit at 80 percent. If you’ve ever noticed lights and basics run for hours on low fuel, then the AC compressor kicks on and the exhaust note deepens, that’s the load shifting in real time.

Realistic hourly fuel use by size and fuel type

Generac publishes fuel consumption tables for each model. Field experience in Charlotte aligns closely with their numbers. Here are practical ranges most homeowners see during an outage:

• 10 to 13 kW air-cooled

• Natural gas: roughly 80 to 110 cubic feet per hour (cfh) at 50 percent load; 140 to 180 cfh at full load.

• Propane: roughly 0.9 to 1.4 gallons per hour (gph) at 50 percent load; 1.6 to 2.3 gph at full load.

• 18 to 22 kW air-cooled

• Natural gas: roughly 150 to 230 cfh at 50 percent load; 250 to 350 cfh at full load.

• Propane: roughly 1.6 to 2.5 gph at 50 percent load; 2.7 to 3.7 gph at full load.

• 24 to 26 kW air-cooled

• Natural gas: roughly 190 to 260 cfh at 50 percent load; 300 to 380 cfh at full load.

• Propane: roughly 2.0 to 2.8 gph at 50 percent load; 3.2 to 4.1 gph at full load.

These are field ranges, not lab-perfect figures. Elevation in Charlotte is modest, so derating for altitude is minimal. Winter blends of propane can slightly vary consumption. Maintenance also matters; a unit with clogged air filters or overdue plugs can run richer and waste fuel.

Converting fuel use into dollars per hour

To translate those numbers into your hourly cost, use current local rates:

• Natural gas: Piedmont Natural Gas and other providers in Mecklenburg County typically land in a range of about $0.90 to $1.60 per therm, including riders and fees. One therm equals 100 cubic feet (ccf). Check your exact bill; the rate changes seasonally and with usage tiers.
• Propane: Delivered LP in the Charlotte area commonly ranges from $2.50 to $3.75 per gallon, with price breaks for larger tanks and pre-buys. During a cold snap, rates can spike above $4.00 for small refills.

Now plug in the numbers.

Example 1: 22 kW Generac on natural gas at 50 percent load

• Consumption: ~190 cfh.
• That’s 1.9 therms per hour.
• At $1.20 per therm, the hourly cost is about $2.28.
• At $1.60 per therm, it’s about $3.04.

Example 2: 22 kW Generac on propane at 50 percent load

• Consumption: ~2.1 gph.
• At $3.00 per gallon, the hourly cost is about $6.30.
• At $3.75 per gallon, the hourly cost is about $7.88.

Example 3: 13 kW Generac on natural gas at 30 percent load

• Consumption: ~70 to 85 cfh.
• That’s 0.7 to 0.85 therms per hour.
• At $1.20 per therm, hourly cost is roughly $0.84 to $1.02.
• At $1.60 per therm, roughly $1.12 to $1.36.

Example 4: 26 kW Generac on propane near full load during a summer outage

• Consumption: ~3.6 to 4.1 gph.
• At $3.25 per gallon, hourly cost is roughly $11.70 to $13.33.

Across Charlotte installations, the most common real-world figure we see for a 18 to 22 kW NG unit carrying normal essentials with one HVAC stage cycling is $2.25 to $3.50 per hour on natural gas. On propane, the same load tends to land between $6.00 and $9.00 per hour. That spread reflects fuel pricing more than equipment efficiency.

Why natural gas is usually cheaper to run in Charlotte

Most homes inside the I-485 loop have access to natural gas. The per-BTU cost tends to beat delivered propane, especially if you’re a steady gas customer. There’s also no truck delivery involved, and you don’t need a large storage tank. That’s why many homeowners in Plaza Midwood, Myers Park, and Steele Creek choose natural gas for standby generators.

Propane still makes sense in parts of Union County, Lake Wylie-adjacent areas, and rural stretches north of Huntersville where gas lines aren’t in place. Propane also offers resilience if a gas main outage is a concern, but that’s rare in Charlotte. If you go propane, we recommend a 250 to 500 gallon tank for meaningful runtime and better refill pricing.

Load management: the biggest lever you control

You influence hourly cost by how you manage loads. A modest change in how and when equipment runs often cuts fuel use by 20 to 40 percent without sacrificing comfort or safety.

Stagger heavy loads so they don’t overlap. Air conditioning compressors, electric ovens, clothes dryers, and well pumps are the main culprits. A load-shedding module or smart transfer switch helps stage high-demand circuits and prevent the generator from bumping into the top range where it drinks hardest. If your system is older, retrofitting a Generac Smart Management Module on select circuits can keep total draw in a sweet spot.

A real example: a Westminster Park homeowner saw his 22 kW propane unit burn 2.5 to 3.0 gph during a July storm because the two-stage AC, electric oven, and pool pump overlapped. By adding two Smart Management Modules and scheduling the pool pump off during outages, his measured consumption dropped to 1.8 to 2.1 gph under the same conditions. In dollars, that was a savings of roughly $3 to $5 per hour at $3.25 propane.

Partial-home vs whole-home: sizing affects cost and comfort

Whole-home systems are popular because the sales pitch is simple, but they are not always the most cost-effective to run. A 26 kW air-cooled unit will idle higher and has a broader appetite even at low load, while a right-sized 14 to 18 kW with managed circuits can keep essentials going for significantly less per hour.

If you’re in a 2,400 square-foot home in SouthPark with gas heat, one 3 to 4 ton AC, gas water heater, and standard kitchen loads, an 18 to 20 kW with load management usually makes more financial sense than a 26 kW set running everything unfiltered. If you have two large AC systems, an induction cooktop, electric dryer, and an EV charger, the calculus changes. This is where a load study helps.

Maintenance and tune: small items, measurable savings

A clean air filter and fresh spark plugs do more than make a technician happy. They improve combustion and reduce wasted fuel. On units we service twice yearly, we see steadier frequency, cleaner waveform, and fuel use at or below published tables. On neglected units, the same load draws 5 to 10 percent more fuel.

Quiet hours matter too. Many Charlotte HOAs require exercise tests during daylight. Generac’s weekly or biweekly exercise is short and uses little fuel, but you can set it to an eco exercise if supported by your model. It runs at lower speed, cutting fuel use during the weekly test. The savings are small over a year, yet the reduced wear is worthwhile.

If you’re searching for “Generac generator service near me” because you suspect your unit’s burning more gas than it used to, start with a basic service visit. We run a load test, check gas pressure under load, clean or replace the air filter, inspect plugs and ignition coils, verify valve lash on models that require it, and confirm the governor and carburation settings are within spec. Small adjustments can bring the per-hour cost back in line.

How long will a propane tank last during an outage?

Homeowners often ask this right after asking the hourly cost. You can estimate runtime with a quick rule: usable gallons divided by gallons per hour equals hours. Use 80 percent of tank capacity as the usable fuel because you should not draw a propane tank to empty, and code limits fill level to roughly 80 percent to allow for expansion.

Example: 500-gallon tank, 80 percent max fill gives 400 gallons. If your 18 kW runs at 2.0 gph on average, you have about 200 hours, or roughly eight days of intermittent use. If you run heavier at 3.0 gph during summer, expect about 133 hours.

In practice, weather, cycling loads, and refill timing change the math. During region-wide outages, propane refill trucks can be delayed. For high-reliability needs in areas without natural gas, we recommend planning for 5 to 7 days of autonomy at your true average gph, not your best case.

Hourly cost versus total outage cost

The per-hour number helps with budgeting, but total outage cost matters more. A 10-hour summer outage at $3 per hour on natural gas costs about $30. Compare that to a thawed freezer, a basement flood from a stopped sump pump, or missed work from a dead office. The generator usually pays for itself the first time it saves a major appliance or prevents water damage.

We also see a secondary benefit in Charlotte neighborhoods exposed to frequent short outages: HVAC systems run shorter recovery cycles, avoiding high-demand restarts that strain compressors. That saves wear, which keeps utility bills and repair costs lower across the season.

What drives higher-than-expected fuel use

If your bill or delivery tickets suggest the unit is burning more than it should, a few common issues rise to the top:

• Dirty air filter or restricted intake. The engine runs rich, fuel goes up, and you smell more exhaust.
• Low or fluctuating gas pressure. With natural gas, undersized or long runs without proper regulators can starve the unit at high load, causing inefficiency and stumbles.
• Overloading or sustained high load. Unmanaged electric heat strips, water heaters, and dryers keep the unit near its top burn rate.
• Aging spark plugs or weak ignition coil. Misfires waste fuel.
• Incorrect altitude or governor settings after a control-board replacement. We see this after DIY board swaps.

A service visit with a combustion check and a clamp-on ammeter reading across major loads usually finds the culprit quickly.

Typical hourly cost bands for Charlotte homeowners

To make planning simple, use these ballpark figures for well-maintained units under normal home loads:

• 10 to 13 kW on natural gas: about $1.00 to $2.00 per hour.
• 18 to 22 kW on natural gas: about $2.25 to $3.50 per hour.
• 24 to 26 kW on natural gas: about $2.75 to $4.25 per hour.
• 10 to 13 kW on propane: about $3.00 to $5.00 per hour.
• 18 to 22 kW on propane: about $6.00 to $9.00 per hour.
• 24 to 26 kW on propane: about $7.50 to $12.50 per hour.

These assume mid-market fuel pricing. If propane spikes, your hourly cost moves with it. If your natural gas rate includes higher riders in winter, the NG numbers move up slightly.

Seasonal differences you will notice in Charlotte

Summer outages are harder on fuel budgets because air conditioning dominates load profiles. Even with gas heat, winter outages usually see lower average load unless you use electric space heaters or have heat pumps running strip heat. Humidity also affects AC runtime. On July evenings in Matthews or Mint Hill, long compressor cycles keep the generator in a higher burn band.

We encourage homeowners to set HVAC to a sensible outage profile. Raise cooling setpoints by two degrees, and lock out pool equipment and electric ovens. Keep your fridge shut. These small steps trim the hourly fuel burn and extend runtime if you are on propane.

Natural gas meter and piping: don’t bottleneck your savings

A clean install does more than look neat on the side wall. Gas meter capacity and piping size affect both performance and fuel economy. Many 18 to 26 kW NG generators ask for 250 to 400 cfh at full load. If your household gas appliances plus the generator exceed your meter’s CFH rating, the generator starves under load. You will see surging, sooty exhaust, and higher burn.

We coordinate meter upsizing with the gas utility in advance for installations in areas like Highland Creek and University City where the original meter was sized for a furnace, water heater, and range. We also use proper diameter runs with minimal elbows to maintain pressure at the unit. This is one of those hidden details that prevents high per-hour costs later.

Homeowner stories: what the numbers look like in practice

A SouthPark family with a 22 kW NG unit saw an average of $2.60 per hour during a 12-hour summer outage. They ran one AC stage, lights, fridge, a gas cooktop, and internet gear. After we added load management on the oven and dryer circuits, their measured draw dropped enough to shave roughly 30 cents per hour on similar days.

In Huntersville, a 20 kW propane system supporting a well pump, septic, and a single heat pump averaged 2.1 gph in spring storms. The homeowners initially expected 1.5 gph from sales literature. The difference? The well pump’s frequent starts during irrigation. We installed a pressure tank with more drawdown and reprogrammed irrigation to suspend during outages. Average fell to 1.7 gph.

In Matthews, a 13 kW NG unit on a ranch home ran essentials at roughly 0.9 therms per hour during a January ice event. That’s about $1.10 to $1.40 per hour with the utility rate at the time. They keep the second refrigerator unplugged during outages and rely on gas logs for living-room heat, which reduces electric load.

How to estimate your own hourly cost accurately

You can make a quick estimate with a simple method. First, identify your generator size and fuel type from the model label. Second, list your likely outage loads: HVAC tonnage and stages, well pump horsepower if applicable, kitchen essentials, and any big electric appliances. Third, use the consumption ranges earlier in this guide to find the 30 to 60 percent load figure for most homes, or the 70 to 90 percent figure if you plan to run the whole house without management. Multiply by your current fuel price.

If you want a precise number, we can perform a 30-minute live load test. We meter gas flow at the meter with a stopwatch method for NG or we use a site glass reading for LP while stepping loads on and off. The data gives a true hourly burn rate for your house as it’s wired and used. It also reveals easy wins for trimming costs.

Service, software, and small settings that matter

Generac firmware settings can alter exercise behavior and voltage/frequency stability, which can influence how certain loads behave. An unsteady frequency makes variable-speed HVAC compressors unhappy and less efficient. Keeping the controller updated and verifying governor parameters during service helps keep everything in the efficient range.

Air intake location also matters, especially in tight side yards common in NoDa and Wesley Heights. If landscaping blocks airflow, engine temperature rises and efficiency slips. We check clearances, recommend trimming or relocating shrubs, and keep the enclosure clean of leaf litter that can clog louvers.

If you’re running Mobile Link monitoring, we can spot patterns in runtime and alert you when a trend suggests clogged filters or declining battery health. Fewer failed starts and smoother runs mean fewer wasteful high-RPM restarts.

Budgeting for outage season in Charlotte

Hurricane remnants and summer thunderstorms drive most outages. A reasonable annual operating budget for a natural gas standby system in Charlotte, including weekly exercise and a few outages, lands in the $40 to $120 range for fuel. Propane users should plan anywhere from $100 to $300 depending on how many hours they run and their tank price. Those numbers exclude maintenance, which is its own line item but prevents fuel waste.

If you’ve never needed the generator for more than an hour or two, it’s easy to forget the ongoing cost is small compared to the value of keeping HVAC, refrigerators, medical devices, and security systems online. Running light and smart keeps the number manageable.

Thinking about a new install or an upgrade?

If you’re comparing quotes around Charlotte and typing “Generac generator service near me,” consider both the installed price and the hourly running cost. A larger unit at a bargain install price can cost more year after year in fuel. A right-sized unit with a smart transfer switch and a couple of load modules can save hundreds in a single long storm, then keep saving for a decade.

For existing systems, a service and load audit often pays for itself within one bad weather season. We look at gas supply, controller settings, maintenance items, and the list of circuits on the transfer switch. We then propose small changes that keep comfort high and burn low.

Ready for clear numbers on your house?

Every home’s usage pattern is different, and local fuel rates change. If you want a precise “per hour” cost for your address in Charlotte, Pineville, Concord, or Fort Mill, we can measure it and give you a straightforward report. We also maintain and repair Generac units across the metro area, from routine service to emergency calls after storms.

Searches for “Generac generator service near me” will turn up a list of options, but if you prefer a team that explains the math, tests under load, and leaves you with lower fuel burn and higher reliability, Ewing Electric Co. is one call away.

Book a service visit, request a load test, or ask for an installation quote. We’ll give you honest numbers, practical recommendations, and a generator that runs cleaner, quieter, and cheaper when you need it most.