★ CONSTRUCTION · HEATING · COMPARISON
Propane wins by $442.03 a season. Propane costs $409.84 a month (136.61 gal) against $498.24 a month for electric (2,930.83 kWh) for the same 10,000,000 BTU a month, because propane is $40.98 per 1,000,000 BTU against $49.82 for electric. Enter your load, fuel prices, furnace efficiency and season length to compare propane with electric heat.
Propane and electric heat are priced on the same thing: the heat the home needs, the price of the fuel, and how much of it becomes heat. Propane is sold by the gallon and electric by the kilowatt-hour, so this calculator turns both into the same heat load and says which one costs less a month and over the whole season, and where the two break even — so the number you get is the number on the bill.
Propane and electric heat are priced on the same heat load, so the fuel price and the efficiency are the only differences. A gallon of propane holds 91,500 BTU, and only the efficiency share of it becomes heat, so the gallons a month are the load divided by 91,500 times the efficiency. A kilowatt-hour holds 3,412 BTU at 100% efficiency, so the kWh a month are the load divided by 3,412. Multiply each by its price for the monthly cost, and multiply by the season months for the season cost.
At the defaults — load 10,000,000 BTU a month, propane $3.00 a gallon, efficiency 80%, electric $0.17 a kWh, season 5 months — propane needs 10,000,000 ÷ (91,500 × 80%) = 136.61 gal a month, which costs 136.61 × $3.00 = $409.84 a month. Electric needs 10,000,000 ÷ 3,412 = 2,930.83 kWh a month, which costs 2,930.83 × $0.17 = $498.24 a month. Over the season that is $409.84 × 5 = $2,049.18 against $498.24 × 5 = $2,491.21, so propane wins by $442.03 a season, $88.41 a month.
| Case | Propane /mo | Electric /mo | Propane season | Electric season | Winner |
|---|---|---|---|---|---|
| Default (10,000,000 BTU/mo, 5 mo) | $409.84 | $498.24 | $2,049.18 | $2,491.21 | Propane by $442.03 |
| Load 5,000,000 BTU/mo | $204.92 | $249.12 | $1,024.59 | $1,245.60 | Propane by $221.01 |
| Load 20,000,000 BTU/mo | $819.67 | $996.48 | $4,098.36 | $4,982.42 | Propane by $884.05 |
| Propane $4.50/gal | $614.75 | $498.24 | $3,073.77 | $2,491.21 | Electric by $582.56 |
| Propane $2.50/gal | $341.53 | $498.24 | $1,707.65 | $2,491.21 | Propane by $783.56 |
| Electric $0.10/kWh | $409.84 | $293.08 | $2,049.18 | $1,465.42 | Electric by $583.76 |
| Electric $0.25/kWh | $409.84 | $732.71 | $2,049.18 | $3,663.54 | Propane by $1,614.36 |
| Efficiency 95% | $345.13 | $498.24 | $1,725.63 | $2,491.21 | Propane by $765.58 |
| Efficiency 70% | $468.38 | $498.24 | $2,341.92 | $2,491.21 | Propane by $149.29 |
| Season 3 months | $409.84 | $498.24 | $1,229.51 | $1,494.72 | Propane by $265.22 |
| Season 6 months | $409.84 | $498.24 | $2,459.02 | $2,989.45 | Propane by $530.43 |
Setup: load 10,000,000 BTU a month, propane $3.00 a gallon, efficiency 80%, electric $0.17 a kWh, season 5 months.
Line 1 — the propane gallons. 10,000,000 ÷ (91,500 × 80%) = 10,000,000 ÷ 73,200 = 136.61 gal a month.
Line 2 — the propane cost. 136.61 × $3.00 = $409.84 a month.
Line 3 — the electric kWh. 10,000,000 ÷ 3,412 = 2,930.83 kWh a month.
Line 4 — the electric cost. 2,930.83 × $0.17 = $498.24 a month.
Line 5 — the season and the winner. $409.84 × 5 = $2,049.18 against $498.24 × 5 = $2,491.21, so propane wins by $442.03 a season, $88.41 a month. Per 1,000,000 BTU that is $40.98 for propane against $49.82 for electric.
Reverse: the propane price breaks even at $3.65 a gallon (exactly 3.6471), and the electric price breaks even at $0.14 a kWh (exactly 0.1398). There is no load break-even, because at fixed prices the cost ratio is load-independent. A $500 a month propane bill is a 12,200,000 BTU a month load, and a $500 a month electric bill is a 10,035,294 BTU a month load.
Load 5,000,000 BTU a month: half the heat is half the fuel on both sides: propane is 10,000,000 ÷ 2 = 5,000,000 BTU, so 68.31 gal at $204.92 a month, and electric is 1,465.42 kWh at $249.12 a month. Propane wins by $44.20 a month, $221.01 a season. The gap halves with the load, because both fuels scale with the load.
Load 20,000,000 BTU a month: twice the heat is twice the fuel: propane is 273.22 gal at $819.67 a month, and electric is 5,861.66 kWh at $996.48 a month. Propane wins by $176.81 a month, $884.05 a season. The gap doubles with the load, because both fuels scale with the load.
Flip — propane $4.50 a gallon: the same 136.61 gal now costs 136.61 × $4.50 = $614.75 a month, while electric stays $498.24. The electric heater wins by $116.51 a month, $582.56 a season. A 50% dearer propane flips the answer, because propane was only $88.41 a month ahead.
Propane $2.50 a gallon: the same 136.61 gal costs 136.61 × $2.50 = $341.53 a month, while electric stays $498.24. Propane wins by $156.71 a month, $783.56 a season. Cheaper propane widens the lead, because every gallon costs $0.50 less.
Flip — electric $0.10 a kWh: the same 2,930.83 kWh now costs 2,930.83 × $0.10 = $293.08 a month, while propane stays $409.84. The electric heater wins by $116.75 a month, $583.76 a season. Cheap electricity flips the answer, because electric was only $88.41 a month behind.
Electric $0.25 a kWh: the same 2,930.83 kWh costs 2,930.83 × $0.25 = $732.71 a month, while propane stays $409.84. Propane wins by $322.87 a month, $1,614.36 a season. Dear electricity is propane’s best case: every kWh costs $0.08 more.
Efficiency 95%: a better furnace squeezes more heat from each gallon: 10,000,000 ÷ (91,500 × 95%) = 115.04 gal, which costs $345.13 a month, while electric stays $498.24. Propane wins by $153.12 a month, $765.58 a season. A 15-point efficiency gain saves $64.71 a month.
Efficiency 70%: an old furnace wastes more heat: 10,000,000 ÷ (91,500 × 70%) = 156.13 gal, which costs $468.38 a month, while electric stays $498.24. Propane wins by only $29.86 a month, $149.29 a season. At 70% efficiency propane is barely ahead, because the wasted heat costs $58.54 a month.
Season 3 months: the monthly costs are the same — $409.84 against $498.24 — but the season is shorter: $409.84 × 3 = $1,229.51 against $498.24 × 3 = $1,494.72. Propane wins by $265.22. A shorter season shrinks the season gap, because the monthly gap only runs for 3 months.
Season 6 months: the monthly costs are the same, but the season is longer: $409.84 × 6 = $2,459.02 against $498.24 × 6 = $2,989.45. Propane wins by $530.43. A longer season widens the season gap, because the monthly gap runs for 6 months.
Reverse — the break-evens: the propane price breaks even at about $3.65 a gallon (exactly $3.6471 a gallon): above that price electric wins, below it propane wins. The electric price breaks even at about $0.14 a kWh (exactly $0.1398 a kWh): above that price propane wins, below it electric wins. There is no load break-even: at fixed prices the cost ratio is the same at any load, so propane is cheaper per BTU at any load at these prices.
The model assumes the same heat load on both fuels, so the fuel price and the efficiency are the only differences, and it assumes the prices stay flat for the whole season, with no price rises. It assumes the electric heater is 100% efficient, the propane furnace is 80% efficient, and the load is the same every month of the season. It leaves out the cost of the furnace and the heater, the propane tank and delivery fees, the electric service charges, and maintenance, which are real but not priced here. Rounding convention: money is rounded to cents, gallons and kWh to two decimals, and all figures are computed from unrounded values, rounded only for display.
| Output | Formula | What it means |
|---|---|---|
| Propane gallons/mo | load ÷ (91,500 × efficiency) | 136.61 gal/mo. |
| Propane cost/mo | gallons/mo × $/gal | $409.84/mo. |
| Electric kWh/mo | load ÷ 3,412 | 2,930.83 kWh/mo. |
| Electric cost/mo | kWh/mo × $/kWh | $498.24/mo. |
| Propane season total | propane cost/mo × months | $2,049.18. |
| Electric season total | electric cost/mo × months | $2,491.21. |
| Winner | lower monthly cost | Propane wins by $88.41/mo. |
| Gap per season | gap/mo × months | $442.03. |
| Gap per month | |propane − electric| per month | $88.41/mo. |
| Cost per 1,000,000 BTU, propane | propane cost/mo ÷ (load ÷ 1,000,000) | $40.98. |
| Cost per 1,000,000 BTU, electric | electric cost/mo ÷ (load ÷ 1,000,000) | $49.82. |
| Load 5,000,000 BTU/mo | same model, half the load | Propane $204.92 vs electric $249.12, Propane wins by $44.20/mo. |
| Load 20,000,000 BTU/mo | same model, double the load | Propane $819.67 vs electric $996.48, Propane wins by $176.81/mo. |
| Propane $4.50/gal | same model, $4.50 | Propane $614.75 vs electric $498.24, Electric wins by $116.51/mo. |
| Propane $2.50/gal | same model, $2.50 | Propane $341.53 vs electric $498.24, Propane wins by $156.71/mo. |
| Electric $0.10/kWh | same model, $0.10 | Propane $409.84 vs electric $293.08, Electric wins by $116.75/mo. |
| Electric $0.25/kWh | same model, $0.25 | Propane $409.84 vs electric $732.71, Propane wins by $322.87/mo. |
| Efficiency 95% | same model, 95% | Propane $345.13 vs electric $498.24, Propane wins by $153.12/mo. |
| Efficiency 70% | same model, 70% | Propane $468.38 vs electric $498.24, Propane wins by $29.86/mo. |
| Season 3 months | same model, 3 months | Propane $1,229.51 vs electric $1,494.72, Propane wins by $88.41/mo. |
| Season 6 months | same model, 6 months | Propane $2,459.02 vs electric $2,989.45, Propane wins by $88.41/mo. |
| Flip: propane $4.50/gal | same model, $4.50 | Propane $614.75 vs electric $498.24, Electric wins by $116.51/mo. |
| Flip 2: electric $0.10/kWh | same model, $0.10 | Propane $409.84 vs electric $293.08, Electric wins by $116.75/mo. |
| Reverse: break-even propane price | tie point of the two monthly costs | $3.65/gal (exactly 3.6471). |
| Reverse: break-even electric price | tie point of the two monthly costs | $0.14/kWh (exactly 0.1398). |
| Extra: load for $500/mo propane | $500 ÷ $/gal × usable BTU/gal | 12,200,000 BTU/mo. |
| Extra: load for $500/mo electric | $500 ÷ $/kWh × 3,412 | 10,035,294 BTU/mo. |
The math is exact for the numbers you enter: the propane gallons are the load divided by 91,500 times the efficiency, the electric kWh are the load divided by 3,412, and the winner is the lower monthly cost. What the model cannot do is read your bills for you: check the propane price on the delivery ticket and the electric price on the bill, because a $4.50 gallon and a $0.10 kWh give opposite answers. It assumes the same load both ways, flat prices, a 100% efficient electric heater, and no equipment, delivery, service or maintenance costs. For the water heater, see gas vs electric water heater; for the furnace itself, see heat pump vs furnace.
Bright Side Kit. "Propane vs Electric Heater: Heating Cost Calculator 2026." https://brightoolbox.com/propane-vs-electric-heater/ Accessed October 25, 2026.Propane, at the defaults. Propane costs $409.84 a month against $498.24 for electric, so propane wins by $88.41 a month and $442.03 over a 5-month season.
The same heat load priced both ways. Propane is the load divided by 91,500 times the efficiency, times the price a gallon; electric is the load divided by 3,412, times the price a kWh. At the defaults that is 136.61 gal at $409.84 a month against 2,930.83 kWh at $498.24 a month.
$40.98, against $49.82 for electric. That is the monthly cost divided by the load in millions of BTU, so it is the fair per-unit comparison at any load.
When propane is dear or electricity is cheap. At $4.50 a gallon propane costs $614.75 a month and electric wins by $116.51 a month; at $0.10 a kWh electric costs $293.08 a month and wins by $116.75 a month.
$3.65 a gallon. The exact break-even is $3.6471 a gallon: above that price electric wins, below it propane wins. The electric price breaks even at $0.14 a kWh (exact 0.1398).
No. At fixed prices the cost ratio is load-independent, so propane is cheaper per BTU at any load at these prices. A bigger home just means a bigger gap: $44.20 a month at 5,000,000 BTU against $176.81 a month at 20,000,000 BTU.
A lot. At 95% efficiency propane costs $345.13 a month and wins by $153.12 a month; at 70% it costs $468.38 a month and wins by only $29.86 a month.
Equipment, delivery and maintenance costs. The model prices the fuel only, and it assumes the electric heater is 100% efficient and the prices stay flat for the season. Check the propane price on the delivery ticket and the electric price on the bill, because a $4.50 gallon and a $0.10 kWh give opposite answers.