How much you actually need
Start with the quantity, because it decides everything else. A mid-sized generator consumes roughly 0.75 gallons an hour at half load. Run continuously, that is 18 gallons a day — which is almost four full five-gallon cans.
| Running pattern | Per day | Over 3 days | Five-gallon cans |
|---|
| Continuous | 18 gal | 54 gal | 11 cans |
|---|
| 12 hours a day | 9 gal | 27 gal | 6 cans |
|---|
| 6 hours a day (blocks) | 4.5 gal | 13.5 gal | 3 cans |
|---|
| 4 hours a day (fridge only) | 3 gal | 9 gal | 2 cans |
|---|
Computed at 0.75 gal/hr, a working figure for a mid-sized generator at half load. Your machine's manual publishes its own consumption — use that number in preference to ours.
Eleven cans is not a plan. It is not legal to store in most garages, it is a serious fire load, and it costs about $220 at the EIA's reported $4.071 a gallon for the week ending 31 August 2026.
Which is why block running is the realistic strategy. Six hours a day keeps a fridge and freezer perfectly safe — FoodSafety.gov puts a sealed fridge at about four hours and a full freezer at about 48 — and needs three cans rather than eleven. The full fuel arithmetic is here.
How long gasoline actually keeps
Less time than people assume, and the ethanol in modern pump gasoline is why. Gasoline oxidizes and forms gums; ethanol absorbs water from the air and eventually separates out, leaving a layer of water and ethanol at the bottom of the tank that an engine cannot run on.
- Untreated in a sealed can: roughly three to six months before starting problems appear.
- Treated with a fuel stabilizer: commonly rated to around 12 to 24 months. Follow the stabilizer's own instructions — products differ and the manufacturer's figure is the one that counts.
- Ethanol-free gasoline: keeps considerably longer, and is worth seeking out for equipment that sits. Sold at marinas and some stations.
- Left in the carburetor: the real killer. Fuel that evaporates in a carburetor leaves varnish that blocks jets, and this is the reason most stored generators will not start.
Which produces one practical rule: rotate it. Put stored gasoline in your car every six months and refill the cans. It costs nothing, since you were going to buy the fuel anyway, and it means the cans always hold fuel that works.
Why propane changes the arithmetic
Propane does not degrade. A 20 lb cylinder bought today will run a generator in ten years exactly as well as it does now. It does not oxidize, it does not absorb water, and it leaves no varnish in a carburetor — which is why dual-fuel generators stored on propane start far more reliably than ones stored on gasoline.
It is also the fuel you can get during a regional outage. Gas station pumps are electric and stop working with the grid; propane exchange cages and pallets do not need power.
The costs are real. Propane carries roughly 10–15% less energy per unit for generator purposes, so rated output drops accordingly — Westinghouse publishes 4,800 running watts on propane against 5,300 on gasoline for the WGen5300DF. And a 20 lb cylinder holds about 4.6 gallons, so a three-day block-running plan needs three cylinders.
One buying note: refill rather than exchange where you can. Exchange cylinders are typically filled to about 15 lb rather than 20, and the price per gallon is substantially higher than the EIA's residential propane figure of $2.674 a gallon for the week ending 30 March 2026, which reflects bulk delivery.
Storing it safely
- Approved containers only. Red, marked for gasoline, with a proper seal. Not a water jug, not an old milk container.
- Never in the house or a basement. Gasoline vapor is heavier than air, settles at floor level, and finds ignition sources — a water heater pilot, a furnace, a light switch.
- A detached shed or the far side of a garage, away from any appliance with a pilot light or an electric motor.
- Check your local limits. Fire codes cap how much gasoline may be stored in a residential garage, and the limit is usually far below eleven cans. Your local fire authority publishes it.
- Propane cylinders outdoors, upright, always. Never in a garage, never in a basement, never on their side. Shaded, on a level surface, away from ignition sources.
- Off the ground and out of direct sun. Heat cycling drives expansion and contraction, which stresses seals on both fuel types.
The maintenance nobody does
The most common generator failure is not running out of fuel. It is a machine that will not start because it sat for a year with stale gasoline in the carburetor.
Twice a year — spring and fall — start the generator, let it run under some load for fifteen minutes, and check the oil. Rotate the stored fuel while you are there. That is the entire schedule, and it is the difference between equipment and an ornament.
If the machine will sit for months, either run the carburetor dry by shutting the fuel valve and letting it stall, or store it on propane. On a dual-fuel machine the second option is free and it is the main reason to buy one.
