What This Calculator Tells You
Check the appliances you'll run — furnace, propane fridge, stove, water heater, generator — enter realistic daily run hours, pick your tank size, and this tool returns gallons burned per day, days per tank, daily BTU load, and cost. Under the hood it treats propane as pure energy: a gallon is ≈ 91,500 BTU, so every appliance's BTU/hr rating times its run hours is just energy leaving your tanks. A 20 lb tank (~430,000 BTU) running a 30,000 BTU/hr furnace lasts about 14 hours of actual burn time — roughly two cold nights at 7 hours of cycling each.
Why Run Hours Matter More Than Nameplate BTU
The furnace and water heater almost never burn continuously — they cycle on a thermostat and on hot-water demand. A furnace rated 30,000 BTU/hr that fires a cumulative 8 hours overnight burns ≈ 240,000 BTU, or about 2.6 gallons, even though it was only "on" part of the time. That's why the honest input here is actual burn hours, not clock hours: enter 8 for a furnace that clicks on and off all night, and 2 for a water heater that reheats in short bursts. Get the run hours right and the days-per-tank number lands close to reality.
Planning a Boondocking Trip
Say you're heading out with two 30 lb tanks (14.2 gal ≈ 1,300,000 BTU) in shoulder-season weather: furnace 6 hr, water heater 1.5 hr, fridge 24 hr, plus some cooking. That's roughly 250,000 BTU a day, so two tanks carry you about five days before you're hunting for a refill. Drop the furnace and you might stretch the same tanks past two weeks. Adjust the hours to match your climate and you can size tanks — or plan resupply stops — before you leave the driveway.
RV Propane Calculator
Check the appliances you're running and enter hours per day for each.
RV Appliance Propane Consumption
Typical BTU ratings and estimated daily propane usage.
| Appliance | BTU/hour | Typical Hours/Day | Gallons/Day | Cost/Day ($3.50) |
|---|---|---|---|---|
| Furnace | 30,000 | 8 | 2.62 | $9.18 |
| Furnace (small) | 20,000 | 8 | 1.75 | $6.12 |
| Water Heater (6 gal) | 12,000 | 2 | 0.26 | $0.92 |
| Water Heater (10 gal) | 16,000 | 2 | 0.35 | $1.22 |
| Stove Burner | 9,000 | 1 | 0.10 | $0.34 |
| Oven | 12,000 | 0.5 | 0.07 | $0.23 |
| Fridge (propane) | 1,500 | 24 | 0.39 | $1.37 |
| Catalytic Heater | 6,000 | 8 | 0.52 | $1.83 |
| Propane Generator | 60,000 | 4 | 2.62 | $9.18 |
| All (moderate use) | — | — | ~3.4 | ~$11.80 |
How to Use This Calculator
- Check the appliances you'll run: Tick furnace, propane fridge, stove/oven, water heater, and generator as they apply. Leave the ones you'll run on shore power or electric unchecked.
- Enter realistic burn hours: For each appliance, enter the hours it will actually fire per day — 6–8 for a furnace cycling overnight, 1–2 for a water heater reheating in bursts, 24 for a propane fridge, not the hours it's merely switched on.
- Set your tanks and price: Pick your tank size (20 / 30 / 40 lb), how many you carry, and your local propane price per gallon so the cost figures match your area.
- Read days per tank: Check gallons per day, days per tank, and daily BTU load. If days per tank is shorter than your trip, add a tank, cut furnace hours, or plan a refill stop.
How It Works
Every propane appliance draws fuel at a fixed BTU/hr rate, and a gallon of propane holds ≈ 91,500 BTU. Multiply each appliance's rating by its daily run hours, add them up, and divide by 91,500 to get gallons burned per day.
The basic rule:
- Each appliance consumes propane based on its BTU/hour rating — furnace ≈ 20,000–30,000, water heater ≈ 10,000–16,000, stove burner ≈ 7,000–9,000, propane fridge ≈ 1,500
- A gallon of liquid propane contains ≈ 91,500 BTU, and each pound holds ≈ 21,600 BTU
- Daily gallons = (total BTU/hr × hours run) ÷ 91,500; days per tank = tank BTU ÷ daily BTU
The furnace dominates the ledger whenever it cycles — one cold night of forced-air heat can outpace a full day of every other appliance combined. A 30 lb tank (7.1 gal ≈ 650,000 BTU) feeding a 30,000 BTU/hr furnace that actually burns 8 hours a night lasts roughly 2.7 nights before it's dry. Cutting furnace runtime, or swapping to a catalytic heater, moves the tank-life needle far more than anything else you can adjust.
Tips & Considerations
- The furnace is almost always your biggest draw — trimming an hour of overnight furnace time saves more propane than switching off every other appliance.
- A catalytic heater (~6,000 BTU/hr) uses a fraction of a 30,000 BTU/hr forced-air furnace and warms a small rig without the blower drain on your battery.
- Run the fridge and water heater on shore power or a generator when you have it — that keeps your propane in reserve for the furnace, where it counts most.
- In cold weather, a single 20 lb tank's vapor draw can struggle to feed a big furnace; two tanks or a 30 lb bottle keeps pressure up as temperatures drop.
- Never plan on running a tank to zero in winter — carry a spare so a dead tank at 2 a.m. doesn't mean a cold night.
Frequently Asked Questions
How long does a 20 lb propane tank last in an RV?
A 20 lb tank holds ≈ 4.7 gallons, or about 430,000 BTU. Run only the propane fridge (1,500 BTU/hr, 24 hr/day = 36,000 BTU/day) plus a little cooking and it stretches close to 10–12 days. Add a 30,000 BTU/hr furnace burning 6–8 hours a night and the same tank empties in about 2 days, because the furnace alone eats 180,000–240,000 BTU per night.
How long does a 30 lb propane tank last in an RV?
A 30 lb tank holds ≈ 7.1 gallons, or about 650,000 BTU — roughly 1.5× a 20 lb tank. Fridge-and-cooking-only usage (≈ 45,000 BTU/day) lasts about two weeks. Moderate boondocking with furnace, water heater, and fridge burns roughly 250,000–300,000 BTU/day, so expect 2–2.5 days per 30 lb tank. Many rigs carry two, doubling those numbers.
How many BTU are in a gallon of propane?
One gallon of liquid propane contains ≈ 91,500 BTU. Per pound it's ≈ 21,600 BTU, which is why a 20 lb tank (4.7 gal) holds about 430,000 BTU and a 30 lb tank (7.1 gal) holds about 650,000 BTU. Tank runtime in hours is simply tank BTU ÷ appliance BTU/hr — a 430,000 BTU tank feeding a single 10,000 BTU/hr water heater at full burn would run 43 hours.
Can I run the furnace and water heater off propane at the same time?
Yes — both draw from the same tank, so their burn rates simply add. A 30,000 BTU/hr furnace plus a 12,000 BTU/hr water heater pulls 42,000 BTU/hr while both fire. They rarely run continuously, though: the water heater only burns while reheating (a few 20-minute cycles a day) and the furnace cycles on the thermostat, so real combined draw is far below the nameplate sum. Enter realistic run hours, not 24, to get an honest daily figure.
How much propane does an RV furnace use per hour?
Most RV forced-air furnaces are rated 20,000–30,000 BTU/hr. At 30,000 BTU/hr the furnace burns 30,000 ÷ 91,500 ≈ 0.33 gallons for every hour it actually fires. On a cold night where the burner runs a cumulative 8 hours, that's ≈ 2.6 gallons — over half a 20 lb tank in a single night.
How do I estimate propane for a boondocking trip?
Add up each appliance's BTU/hr × the hours you expect it to actually burn, divide by 91,500 for gallons per day, then multiply by your trip length. A summer trip on fridge and cooking alone runs well under a gallon a day; a winter trip leaning on the furnace can top 3 gallons a day. Size your tanks to the total plus a margin, and remember cold weather both raises furnace demand and slightly lowers the vapor draw a single tank can supply.
What uses the most propane in an RV?
The furnace, by a wide margin. At 30,000 BTU/hr it can burn as much in one cold night as the propane fridge does in an entire week. The water heater is a distant second when it's recovering hot water, the stove/oven a minor third, and the fridge in propane mode (≈ 1,500 BTU/hr, roughly 0.4 gal/day) is the most frugal thing on board.