Propane vs Electric Heating: Cost Per Million BTU Compared

What does $34.51 per million BTU mean?

It means a million BTU of heat delivered by propane costs $34.51 when propane is $3.00 a gallon and the furnace is 95% efficient: a gallon carries 91,500 BTU, the furnace delivers 86,925 BTU of it, and a million divided by 86,925 is 11.5038 gallons, which at $3.00 a gallon is $34.51. Electricity at $0.16 a kWh carries 3,412 BTU a kWh at 100%, so a million BTU needs 293.08 kWh and costs $46.89. The gap is $12.38 per million BTU, and over a 50 million BTU year it is $619.04 — $1,725.63 against $2,344.67, 575.2 gallons against 14,654 kWh. Propane at $4.00 a gallon costs $46.02 per million BTU against $46.89 for electricity — a gap of $0.88.

Three things to check before you trust the number

Use your all-in electricity rate, not the supply rate. A bill that quotes $0.10 a kWh for supply and $0.06 a kWh for delivery is $0.16 a kWh all-in, and at $0.10 the answer flips to electricity by $5.20 per million BTU. If the calculator says propane wins and your bill says otherwise, the rate you typed is usually the reason — the delivery charge is real money, and it belongs in the comparison.

Furnace efficiency is the propane side’s quiet variable. A 95% furnace makes propane cost $34.51 per million BTU; an 80% furnace makes it $40.98; a 50% furnace makes it $65.57, and electricity wins outright. Before you compare fuels, check the furnace: a bad furnace is worth replacing before the fuel is worth switching, and the rating plate or the manual has the number.

The break-even is a price, not a verdict. Electricity would need to fall to $0.12 a kWh — $0.117757 exactly — for the two to tie at $3.00 propane and 95% efficiency. If your electricity is $0.1178 a kWh, the gap is $0.01 per million BTU and the saving is $0.63 a year: a rounding error, not a decision. Near the break-even, the fuel choice is a coin toss and the real question is the equipment, the tank, and the wiring.

Worked example

On the defaults: propane $3.00 a gallon, 95% efficiency, electricity $0.16 a kWh, 50 million BTU a year.

1. Propane heat per gallon: 91,500 × 0.95 = 86,925 BTU delivered per gallon.
2. Gallons per million BTU: 1,000,000 ÷ 86,925 = 11.5038 gallons.
3. Propane cost per million BTU: 11.5038 × $3.00 = $34.51 ($34.512511 at 6dp).
4. kWh per million BTU: 1,000,000 ÷ 3,412 = 293.08 kWh.
5. Electricity cost per million BTU: 293.08 × $0.16 = $46.89 ($46.893318 at 6dp).
6. Gap: $46.89 − $34.51 = $12.38 per million BTU ($12.380807 at 6dp).
7. Annual costs: $34.51 × 50 = $1,725.63 propane; $46.89 × 50 = $2,344.67 electricity.
8. Annual saving: $2,344.67 − $1,725.63 = $619.04 ($619.040346 at 6dp).
9. Fuel burned: 50 × 11.5038 = 575.2 gallons of propane (575.208513 at 6dp); 50 × 293.08 = 14,654 kWh (14,654.161782 at 6dp).
10. Break-even: $34.51 per million BTU × 3,412 ÷ 1,000,000 = $0.12 a kWh ($0.117757 at 6dp).
11. The other headline: propane at $4.00 a gallon costs $46.02 per million BTU against $46.89 for electricity — a gap of $0.88, and $43.83 a year.
12. Largest propane price for propane to still win: $4.00 a gallon — and $4.25 a gallon flips it, electricity winning by $2.00 per million BTU.

Every branch, checked

• Propane $3.50 a gallon: Propane $3.50 a gallon: Propane $2,013.23/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $331.44/yr (propane $40.26/MMBtu, electric $46.89/MMBtu). propane at $3.50 a gallon costs $40.26 per million BTU against $46.89 for electricity — a gap of $6.63, and $331.44 a year on a 50 million BTU load; propane still wins, but the lead is half what it was at $3.00
• Propane $2.50 a gallon: Propane $2.50 a gallon: Propane $1,438.02/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $906.64/yr (propane $28.76/MMBtu, electric $46.89/MMBtu). propane at $2.50 a gallon costs $28.76 per million BTU against $46.89 — a gap of $18.13, and $906.64 a year; the cheaper the propane, the wider the lead
• Electricity $0.12 a kWh: Electricity $0.12 a kWh: Propane $1,725.63/yr vs electric $1,758.50/yr over 50 MMBtu — Propane wins by $32.87/yr (propane $34.51/MMBtu, electric $35.17/MMBtu). electricity at $0.12 a kWh costs $35.17 per million BTU against $34.51 for propane — a gap of $0.66, and $32.87 a year; propane wins by a hair, and the break-even electricity price is $0.12 a kWh
• Electricity $0.10 a kWh: Electricity $0.10 a kWh: Propane $1,725.63/yr vs electric $1,465.42/yr over 50 MMBtu — Electric wins by $260.21/yr (propane $34.51/MMBtu, electric $29.31/MMBtu). electricity at $0.10 a kWh costs $29.31 per million BTU against $34.51 for propane — electricity wins by $5.20 per million BTU, and $260.21 a year; below the break-even price the answer flips
• Furnace 80% efficient: Furnace 80% efficient: Propane $2,049.18/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $295.49/yr (propane $40.98/MMBtu, electric $46.89/MMBtu). a furnace at 80% efficiency makes propane cost $40.98 per million BTU against $46.89 — a gap of $5.91, and $295.49 a year; a worse furnace shrinks the lead but does not erase it at these prices
• Load 80 MMBtu a year: Load 80 MMBtu a year: Propane $2,761.00/yr vs electric $3,751.47/yr over 80 MMBtu — Propane wins by $990.46/yr (propane $34.51/MMBtu, electric $46.89/MMBtu). an 80 million BTU load costs $2,761.00 for propane against $3,751.47 for electricity — a gap of $990.46 a year; the bigger the house, the bigger the saving, because the per-million-BTU gap does not change
• Propane $4.00 a gallon: Propane $4.00 a gallon: Propane $2,300.83/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $43.83/yr (propane $46.02/MMBtu, electric $46.89/MMBtu). propane at $4.00 a gallon costs $46.02 per million BTU against $46.89 for electricity — a gap of $0.88, and $43.83 a year; propane wins by a hair, and a little more expensive and the answer flips
• Electricity $0.20 a kWh: Electricity $0.20 a kWh: Propane $1,725.63/yr vs electric $2,930.83/yr over 50 MMBtu — Propane wins by $1,205.21/yr (propane $34.51/MMBtu, electric $58.62/MMBtu). electricity at $0.20 a kWh costs $58.62 per million BTU against $34.51 for propane — a gap of $24.10, and $1,205.21 a year; expensive electricity makes propane the clear winner
• Propane $2.00 a gallon at 90%: Propane $2.00 a gallon at 90%: Propane $1,214.33/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $1,130.34/yr (propane $24.29/MMBtu, electric $46.89/MMBtu). propane at $2.00 a gallon with a 90% furnace costs $24.29 per million BTU against $46.89 — a gap of $22.61, and $1,130.34 a year; cheap fuel beats even a mediocre furnace
• Load 30 MMBtu a year: Load 30 MMBtu a year: Propane $1,035.38/yr vs electric $1,406.80/yr over 30 MMBtu — Propane wins by $371.42/yr (propane $34.51/MMBtu, electric $46.89/MMBtu). a 30 million BTU load costs $1,035.38 for propane against $1,406.80 for electricity — a gap of $371.42 a year; the saving scales with the load, so a small house saves less in dollars

The reverses, worked backwards

• Largest propane price ($0.25 steps) for propane to still win: $4.00/gal — at $4.00/gal the figures are Propane $2,300.83/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $43.83/yr (propane $46.02/MMBtu, electric $46.89/MMBtu) (propane raw 46.016681, electric raw 46.893318, gap raw 0.876637, annual saving raw 43.831833, break-even 0.157009/kWh); at the upper neighbor the figures are Propane $2,444.64/yr vs electric $2,344.67/yr over 50 MMBtu — Electric wins by $99.97/yr (propane $48.89/MMBtu, electric $46.89/MMBtu) (propane raw 48.892724, electric raw 46.893318, gap raw −1.999406, annual saving raw −99.970296, break-even 0.166822/kWh); at the lower neighbor the figures are Propane $2,157.03/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $187.63/yr (propane $43.14/MMBtu, electric $46.89/MMBtu) (propane raw 43.140638, electric raw 46.893318, gap raw 3.752679, annual saving raw 187.633961, break-even 0.147196/kWh) — verdict: STEP.
• Largest electricity price ($0.01 steps) for electric to win: $0.11/kWh — at $0.11/kWh the figures are Propane $1,725.63/yr vs electric $1,611.96/yr over 50 MMBtu — Electric wins by $113.67/yr (propane $34.51/MMBtu, electric $32.24/MMBtu) (propane raw 34.512511, electric raw 32.239156, gap raw −2.273355, annual saving raw −113.667743, break-even 0.117757/kWh); at the upper neighbor the figures are Propane $1,725.63/yr vs electric $1,758.50/yr over 50 MMBtu — Propane wins by $32.87/yr (propane $34.51/MMBtu, electric $35.17/MMBtu) (propane raw 34.512511, electric raw 35.169988, gap raw 0.657477, annual saving raw 32.873875, break-even 0.117757/kWh); at the lower neighbor the figures are Propane $1,725.63/yr vs electric $1,465.42/yr over 50 MMBtu — Electric wins by $260.21/yr (propane $34.51/MMBtu, electric $29.31/MMBtu) (propane raw 34.512511, electric raw 29.308324, gap raw −5.204187, annual saving raw −260.209361, break-even 0.117757/kWh) — verdict: STEP.
• Smallest furnace efficiency (5-pt steps) for propane to win: 70% — at 70% the figures are Propane $2,341.92/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $2.75/yr (propane $46.84/MMBtu, electric $46.89/MMBtu) (propane raw 46.838407, electric raw 46.893318, gap raw 0.054910, annual saving raw 2.745510, break-even 0.159813/kWh); at the lower neighbor the figures are Propane $2,522.07/yr vs electric $2,344.67/yr over 50 MMBtu — Electric wins by $177.40/yr (propane $50.44/MMBtu, electric $46.89/MMBtu) (propane raw 50.441362, electric raw 46.893318, gap raw −3.548044, annual saving raw −177.402211, break-even 0.172106/kWh); at the upper neighbor the figures are Propane $2,185.79/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $158.87/yr (propane $43.72/MMBtu, electric $46.89/MMBtu) (propane raw 43.715847, electric raw 46.893318, gap raw 3.177471, annual saving raw 158.873535, break-even 0.149158/kWh) — verdict: STEP.
• Largest propane price ($0.50 steps) for annual saving of $1,000 or more: $2.00/gal — at $2.00/gal the figures are Propane $1,150.42/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $1,194.25/yr (propane $23.01/MMBtu, electric $46.89/MMBtu) (propane raw 23.008341, electric raw 46.893318, gap raw 23.884977, annual saving raw 1194.248859, break-even 0.078504/kWh); at the upper neighbor the figures are Propane $1,438.02/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $906.64/yr (propane $28.76/MMBtu, electric $46.89/MMBtu) (propane raw 28.760426, electric raw 46.893318, gap raw 18.132892, annual saving raw 906.644602, break-even 0.098131/kWh); at the lower neighbor the figures are Propane $862.81/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $1,481.85/yr (propane $17.26/MMBtu, electric $46.89/MMBtu) (propane raw 17.256255, electric raw 46.893318, gap raw 29.637062, annual saving raw 1481.853115, break-even 0.058878/kWh) — verdict: STEP.
• Smallest annual load (10-MMBtu steps) for annual saving of $500 or more: 50 MMBtu — at 50 MMBtu the figures are Propane $1,725.63/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $619.04/yr (propane $34.51/MMBtu, electric $46.89/MMBtu) (propane raw 34.512511, electric raw 46.893318, gap raw 12.380807, annual saving raw 619.040346, break-even 0.117757/kWh); at the lower neighbor the figures are Propane $1,380.50/yr vs electric $1,875.73/yr over 40 MMBtu — Propane wins by $495.23/yr (propane $34.51/MMBtu, electric $46.89/MMBtu) (propane raw 34.512511, electric raw 46.893318, gap raw 12.380807, annual saving raw 495.232277, break-even 0.117757/kWh); at the upper neighbor the figures are Propane $2,070.75/yr vs electric $2,813.60/yr over 60 MMBtu — Propane wins by $742.85/yr (propane $34.51/MMBtu, electric $46.89/MMBtu) (propane raw 34.512511, electric raw 46.893318, gap raw 12.380807, annual saving raw 742.848415, break-even 0.117757/kWh) — verdict: STEP.
• Smallest electricity price ($0.02 steps) for propane to win by $10/MMBtu or more: $0.16/kWh — at $0.16/kWh the figures are Propane $1,725.63/yr vs electric $2,344.67/yr over 50 MMBtu — Propane wins by $619.04/yr (propane $34.51/MMBtu, electric $46.89/MMBtu) (propane raw 34.512511, electric raw 46.893318, gap raw 12.380807, annual saving raw 619.040346, break-even 0.117757/kWh); at the lower neighbor the figures are Propane $1,725.63/yr vs electric $2,051.58/yr over 50 MMBtu — Propane wins by $325.96/yr (propane $34.51/MMBtu, electric $41.03/MMBtu) (propane raw 34.512511, electric raw 41.031653, gap raw 6.519142, annual saving raw 325.957110, break-even 0.117757/kWh); at the upper neighbor the figures are Propane $1,725.63/yr vs electric $2,637.75/yr over 50 MMBtu — Propane wins by $912.12/yr (propane $34.51/MMBtu, electric $52.75/MMBtu) (propane raw 34.512511, electric raw 52.754982, gap raw 18.242472, annual saving raw 912.123581, break-even 0.117757/kWh) — verdict: STEP.

What the defaults assume

The defaults are propane at $3.00 a gallon, a 95% furnace, electricity at $0.16 a kWh, and a 50 million BTU home — a mid-size house in a cold climate, with fuel prices near recent averages. They are a starting point, not a standard: your propane price is on your delivery ticket, your electricity price is on your bill, your furnace efficiency is on the rating plate, and your load is on your heat-load calculation or last year’s fuel use. Change the four inputs to your own and the calculator recomputes instantly. Divide the price by the delivered heat, multiply by the load, and the break-even is the electricity price where the two tie.

These notes repeat in every explainer section because this page is built to be read start to finish: the defaults are one house, not a standard; use your all-in electricity rate, not the supply rate; furnace efficiency is the propane side’s quiet variable; and the break-even is a price, not a verdict.

Output · formula · meaning

Who uses this

• A homeowner with a propane tank deciding whether to keep it — at $3.00 a gallon and $0.16 a kWh propane saves $619.04 a year, and the break-even electricity price is $0.12 a kWh, so the tank stays unless the electricity rate falls.
• A homeowner on electric resistance heat weighing a propane furnace — at $0.10 a kWh electricity wins by $260.21 a year, so the switch only pays if the electricity rate is high or the propane price is low.
• A landlord choosing the heating for a rental — the per-million-BTU gap is the same whatever the house, but the dollars scale with the load: $371.42 a year on a 30 million BTU house, $990.46 on an 80 million BTU one.
• An energy auditor checking a client’s numbers — the 575.2 gallons and 14,654 kWh are the fuel the house actually burns, and the break-even of $0.117757 a kWh is the number to watch when rates change.

Accuracy & limitations

The calculator compares the cost of delivered heat exactly — every figure on this page is checked against an independent model, and the propane and electricity numbers use the standard energy contents (91,500 BTU a gallon, 3,412 BTU a kWh) and your furnace efficiency. What it does not do is price the equipment: a propane furnace, a tank, a gas line, a panel upgrade and an electric furnace all cost money, and the fuel saving has to pay for them before the switch pays. It does not price delivery fees, tank rental, minimum delivery charges or time-of-use electricity rates, and it does not model a heat pump, which moves heat instead of making it and can beat both fuels on cost — the heat-pump-vs-furnace page is the one for that. It assumes the furnace efficiency is constant, which is close enough for a comparison but not exact across a whole winter. It is not a quote: your propane supplier and your electric utility set your prices, and this page tells you what those prices mean, not what they will be.

Cite this calculator

Propane at $3.00 a gallon, 95% efficient, costs $34.51 per million BTU; electricity at $0.16 a kWh costs $46.89. On a 50 MMBtu load: $1,725.63 vs $2,344.67, saving $619.04 a year; 575.2 gallons vs 14,654 kWh; break-even electricity price $0.117757 a kWh. Largest propane price for propane to still win: $4.00 a gallon. Largest electricity price for electric to win: $0.11 a kWh. Smallest furnace efficiency for propane to win: 70%. Largest propane price for annual saving of $1,000 or more: $2.00 a gallon. Smallest annual load for annual saving of $500 or more: 50 MMBtu. Smallest electricity price for propane to win by $10/MMBtu or more: $0.16 a kWh. Source: Bright Side Kit, brightoolbox.com.

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