A typical home standby generator uses 2–4 gallons of propane per hour at full load, or 1–2 gallons per hour at the 50% load you will run during most outages. A 22kW generator — the most popular size for whole-home backup — burns approximately 2.5 gallons per hour at 75% load, costing about $7.00/hour at 2026 propane prices.
Those numbers determine everything: how big your tank needs to be, how much each outage costs, and how long you can run before needing a refill. Below are the exact consumption rates for every common generator size, along with tank runtime charts and a calculator you can use for your specific setup.
Propane Consumption by Generator Size
Propane consumption varies dramatically by generator size and load. The table below covers every popular residential standby and portable generator size.
| Generator Size | 25% Load | 50% Load | 75% Load | 100% Load |
|---|---|---|---|---|
| 3,500W Portable | 0.3 gal/hr | 0.5 gal/hr | 0.7 gal/hr | 0.9 gal/hr |
| 5,500W Portable | 0.4 gal/hr | 0.7 gal/hr | 1.0 gal/hr | 1.3 gal/hr |
| 7,500W Portable | 0.5 gal/hr | 0.9 gal/hr | 1.3 gal/hr | 1.7 gal/hr |
| 10kW Standby | 0.6 gal/hr | 1.1 gal/hr | 1.5 gal/hr | 1.9 gal/hr |
| 14kW Standby | 0.8 gal/hr | 1.4 gal/hr | 2.0 gal/hr | 2.6 gal/hr |
| 16kW Standby | 0.9 gal/hr | 1.5 gal/hr | 2.2 gal/hr | 2.9 gal/hr |
| 20kW Standby | 1.0 gal/hr | 1.8 gal/hr | 2.7 gal/hr | 3.5 gal/hr |
| 22kW Standby | 1.1 gal/hr | 2.0 gal/hr | 2.9 gal/hr | 3.8 gal/hr |
| 24kW Standby | 1.2 gal/hr | 2.2 gal/hr | 3.1 gal/hr | 4.1 gal/hr |
| 26kW Standby | 1.3 gal/hr | 2.3 gal/hr | 3.4 gal/hr | 4.4 gal/hr |
| 30kW Standby | 1.5 gal/hr | 2.7 gal/hr | 3.9 gal/hr | 5.1 gal/hr |
| 38kW Standby | 1.8 gal/hr | 3.3 gal/hr | 4.9 gal/hr | 6.4 gal/hr |
| 48kW Standby | 2.3 gal/hr | 4.1 gal/hr | 6.1 gal/hr | 8.0 gal/hr |
Why 50% load matters most: During a typical power outage, your generator cycles between high-draw periods (AC compressor on, water heater heating) and low-draw periods (just lights and fridge). The average load over a 24-hour period is usually 40–60% of rated capacity. Use the 50% column for the most realistic runtime and cost estimates.
How Long Will Your Propane Tank Last?
The runtime of your propane tank depends on three things: tank size, fill level (tanks are filled to 80% capacity for thermal expansion safety), and your average consumption rate.
| Tank Size | Usable Gallons (80% fill) | Runtime at 25% Load | Runtime at 50% Load | Runtime at 75% Load | Runtime at 100% Load |
|---|---|---|---|---|---|
| 100-gallon | 80 gallons | 73 hrs (3 days) | 40 hrs (1.7 days) | 28 hrs (1.2 days) | 21 hrs |
| 120-gallon | 96 gallons | 87 hrs (3.6 days) | 48 hrs (2 days) | 33 hrs (1.4 days) | 25 hrs |
| 250-gallon | 200 gallons | 182 hrs (7.6 days) | 100 hrs (4.2 days) | 69 hrs (2.9 days) | 53 hrs (2.2 days) |
| 500-gallon | 400 gallons | 364 hrs (15 days) | 200 hrs (8.3 days) | 138 hrs (5.7 days) | 105 hrs (4.4 days) |
| 1,000-gallon | 800 gallons | 727 hrs (30 days) | 400 hrs (16.7 days) | 276 hrs (11.5 days) | 211 hrs (8.8 days) |
| Tank Size | Usable Gallons | Runtime at 25% Load | Runtime at 50% Load | Runtime at 75% Load | Runtime at 100% Load |
|---|---|---|---|---|---|
| 100-gallon | 80 gallons | 100 hrs (4.2 days) | 57 hrs (2.4 days) | 40 hrs (1.7 days) | 31 hrs (1.3 days) |
| 250-gallon | 200 gallons | 250 hrs (10.4 days) | 143 hrs (6 days) | 100 hrs (4.2 days) | 77 hrs (3.2 days) |
| 500-gallon | 400 gallons | 500 hrs (20.8 days) | 286 hrs (11.9 days) | 200 hrs (8.3 days) | 154 hrs (6.4 days) |
Never run your propane tank completely empty. Most generators will shut down when tank pressure drops below a safe level (around 10–15% remaining). Plan your refill when the tank reaches 20–25%. During widespread outages, propane delivery may be delayed by days or weeks.
Propane Cost Per Hour and Per Day
Using the national average propane price of $2.80 per gallon in early 2026, here is what you will pay to run your generator.
| Generator Size | 25% Load | 50% Load | 75% Load | 100% Load |
|---|---|---|---|---|
| 10kW | $1.68/hr | $3.08/hr | $4.20/hr | $5.32/hr |
| 14kW | $2.24/hr | $3.92/hr | $5.60/hr | $7.28/hr |
| 16kW | $2.52/hr | $4.20/hr | $6.16/hr | $8.12/hr |
| 20kW | $2.80/hr | $5.04/hr | $7.56/hr | $9.80/hr |
| 22kW | $3.08/hr | $5.60/hr | $8.12/hr | $10.64/hr |
| 24kW | $3.36/hr | $6.16/hr | $8.68/hr | $11.48/hr |
| Generator Size | Gallons/Day | Daily Cost at $2.80/gal | 3-Day Cost | 7-Day Cost |
|---|---|---|---|---|
| 10kW | 26.4 gal | $73.92 | $221.76 | $517.44 |
| 14kW | 33.6 gal | $94.08 | $282.24 | $658.56 |
| 16kW | 36.0 gal | $100.80 | $302.40 | $705.60 |
| 20kW | 43.2 gal | $120.96 | $362.88 | $846.72 |
| 22kW | 48.0 gal | $134.40 | $403.20 | $940.80 |
| 24kW | 52.8 gal | $147.84 | $443.52 | $1,034.88 |
Propane Tank Sizing Guide
Choosing the right tank size is critical. Too small, and you run out mid-outage. Too large, and you waste money on a tank you do not need.
| Generator Size | 24-Hour Backup | 3-Day Backup | 7-Day Backup | 14-Day Backup |
|---|---|---|---|---|
| 10kW | 120-gallon | 250-gallon | 500-gallon | 1,000-gallon |
| 14kW | 120-gallon | 250-gallon | 500-gallon | 1,000-gallon |
| 16kW | 250-gallon | 250-gallon | 500-gallon | 1,000-gallon |
| 20kW | 250-gallon | 500-gallon | 1,000-gallon | 1,000-gallon |
| 22kW | 250-gallon | 500-gallon | 1,000-gallon | 1,000-gallon |
| 24kW+ | 250-gallon | 500-gallon | 1,000-gallon | 2× 500-gallon |
| Tank Size | Tank Purchase Price | Tank Lease (Annual) | Fill Cost at $2.80/gal |
|---|---|---|---|
| 100-gallon | $400–$800 | $40–$80/yr | $224 |
| 120-gallon | $500–$900 | $50–$90/yr | $269 |
| 250-gallon | $800–$1,500 | $75–$150/yr | $560 |
| 500-gallon | $1,200–$2,500 | $100–$200/yr | $1,120 |
| 1,000-gallon | $2,000–$4,000 | $150–$300/yr | $2,240 |
Most propane companies offer tank leasing programs where you pay a small annual fee ($75–$200) instead of buying the tank outright. The catch: you must buy propane exclusively from that company. If you have competitive propane pricing in your area, owning your tank gives you the freedom to shop for the best rates.
How Temperature Affects Propane Consumption
Propane is stored as a liquid under pressure. When it gets cold, the liquid's ability to vaporize (turn into gas) decreases. This has two effects on your generator.
Below 0°F, a propane tank may not vaporize fuel fast enough to keep a large generator running at full load. This is called "freeze-up" and it is more common with smaller tanks that have less liquid surface area for vaporization.
Cold weather also increases your electrical load because your heating system runs harder, which means the generator consumes more propane. A 22kW generator that averages 50% load in summer may average 70% load in winter.
| Temperature Range | Vaporization Rate Impact | Typical Load Increase | Practical Effect |
|---|---|---|---|
| Above 40°F | No impact | None (summer baseline) | Normal operation |
| 20°F to 40°F | Minimal impact | +10–15% (heating load) | Slight increase in consumption |
| 0°F to 20°F | Moderate — small tanks may struggle | +20–30% (heavy heating) | Consider 500+ gallon tank |
| Below 0°F | Significant — may need tank heater | +30–50% (extreme heating) | Tank warmer recommended for tanks under 250 gallons |
Propane Usage Calculator
This calculator is being re-verified
We’re auditing all of our calculators against primary-source standards (ENERGY STAR, DOE, ACCA Manual J, NEC) and re-publishing each once its math is confirmed. This one will be back shortly.
Propane vs. Other Generator Fuels: Consumption Comparison
To put propane consumption in perspective, here is how it compares to other fuels for the same 20kW generator at 50% load.
| Fuel | Consumption Rate | Cost/Hour | Cost/24 Hours | Cost/72 Hours |
|---|---|---|---|---|
| Propane (LP) | 1.8 gal/hr | $5.04/hr | $120.96 | $362.88 |
| Gasoline | 1.2 gal/hr | $3.84/hr | $92.16 | $276.48 |
| Natural Gas | 200 CFH | $2.40/hr | $57.60 | $172.80 |
| Diesel | 0.9 gal/hr | $3.42/hr | $82.08 | $246.24 |
Wait — gasoline costs less per hour? Yes, at current prices, gasoline has a lower hourly cost than propane because gasoline has more energy per gallon (120,238 BTU vs. 91,500 BTU). However, propane has other advantages: indefinite shelf life, cleaner combustion, lower maintenance costs, and on-site tank storage that does not depend on gas station availability.
Key Takeaways:
- Real-world 22kW draw averages ~2.0 gal/hr because outages cycle between high-draw appliances (AC compressor, water heater) and low-draw idle (fridge, lights) — the 3.8 gal/hr nameplate rating only appears at continuous 100% load.
- At $2.80/gallon, that is $5.60/hour or $134/day for whole-home backup.
- A 500-gallon tank provides roughly 8 days of runtime at 50% load for a 22kW generator.
- Use the 50% load column for the most realistic estimates — that is what most homes average.
- Cold weather increases both propane consumption (higher load) and may reduce tank vaporization.
- Tank size recommendation: 250-gallon for 3-day backup, 500-gallon for 7-day backup.
- Never let your tank drop below 20% — schedule refills early during outage season.
Frequently Asked Questions
A 100-pound propane tank holds approximately 23.6 gallons. On a 22kW generator at 50% load (2.0 gal/hr), it lasts about 12 hours. On a smaller 5,500W portable at 50% load (0.7 gal/hr), it lasts approximately 34 hours.