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G-024 · REV 2 · CHECKED 2026-10-09 · MODEL v1.0.2 ▾

Drafted with AI assistance. Numbers computed by model v1.0.2 or sourced. Human review: pending (BayHeat editorial desk). Licensed review: no page-specific approval recorded.

Technical review: no page-specific licensed approval recorded.

M measured · C computed · S spec · R reference · E estimate

Electric vs propane garage heaters

In Illinois, electric resistance heat runs about $56/MMBtu delivered; a vented propane unit heater runs about $28/MMBtu; natural gas about $14/MMBtu; a diesel air heater about $62/MMBtu. None of those rankings hold in every state — your own electricity and fuel prices decide the order, not a national rule of thumb.

The Fuel Cost Meter: $/MMBtu delivered, by state

This is the delivered cost of one million BTU of actual heat in the garage — the fuel's price per gallon, therm or kWh, divided by how much of that energy the equipment class actually turns into heat. Electric resistance runs at efficiency because every watt becomes heat in the room; a vented gas or propane unit heater runs about because some heat leaves with the flue gas; a diesel air heater runs about .

StateElectricPropane (vented)Natural gasDiesel
Illinois$56$28$14$62
California$97$43$27$77
Texas$47$41$23$58
US average$53$37$19$61

Per million BTU delivered, computed live from each state's EIA price and the efficiency figures above — not a flat national average stretched across every state.

What that looks like for a real garage

For BayHeat's standard worked example — a 24×24 ft attached two-car garage in Chicago, needing about — here's the season cost of covering that same load on each system, at Illinois prices:

Electric
$1.63/h
Heat pump
$0.61/h
Natural gas
$0.39/h
Propane (bulk)
$0.80/h
Propane (cylinder)
$1.04/h
Diesel
$1.81/h

Natural gas is cheapest per MMBtu almost everywhere it's piped to the garage. The catch: most detached garages don't have a gas line. Running one plus a B-vent through the roof is its own project. Propane trades a cylinder or bulk tank for that piping. Electric needs neither, at the cost of the highest rate per MMBtu in most states.

A heat pump mini-split moves heat instead of making it, so its effective efficiency runs well over — see the mini-split page for a real seasonal-COP worked example before assuming electric always means resistance heat.

Don't pick by rate alone

  • Why not a Forced-air "torpedo" heater (never recommended)? A forced-air torpedo heater burns cylinder propane unvented at up to 200,000 BTU/h. It's a construction/outdoor tool — running one indoors, vented or not, isn't part of this comparison.
  • Why not a Diesel air heater (unlisted for building heat)? A diesel air heater isn't UL-listed for permanent building heat. Its low rate above only makes sense for occasional or outdoor use, with the exhaust run outside every time — not as a year-round system.

Where to look

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ELECTRIC · 240V SHOP · 7.5 KW

Dr. Infrared DR-975

No fuel line, no venting — plug into the numbers on the electric page and size the circuit first.

Manual: “WARNING – RISK OF FIRE, DO NOT USE AS A RESIDENTIAL OR HOUSEHOLD HEATER.” Also not where gasoline, paint or flammable liquids are used or stored. Ask Dr. Infrared whether your garage counts as residential before you buy.

Check price on Amazon

Price class: $$$

VENTED GAS UNIT HEATER

Mr. Heater Big Maxx (NG/propane)

Cheapest rate above, on either fuel — but budget for the gas line, regulator and vent run before comparing it to a plug-and-go electric unit. See the natural gas page for sizing and venting, and the propane page for the safety conditions.

BayHeat advises a licensed gas fitter and the permit your town requires. Manual: in a residential garage the bottom of the heater must be at least 8 ft above the floor. Never where gasoline, solvents, paint thinner or dust are present.

Check price on Amazon

Price class: $$$

Safety, whichever fuel wins on price

Any fuel-fired heater with a pilot, burner or spark needs its ignition source at least — an unvented cylinder heater and a vented unit heater both count. A diesel or gas unit heater's exhaust has to leave the building, not just the garage bay. None of that changes based on which fuel is cheapest this month. General information. Your electrician, gas fitter, local code and the heater's manual govern.

Safety add-on

Kidde C3010 10-year sealed-battery CO alarm (UL 2034)

Put a UL 2034 CO alarm in the house, by the garage door and outside each sleeping area.

Paid links: we earn a commission if you buy through links on this page, at no cost to you. As an Amazon Associate, BayHeat earns from qualifying purchases.

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Data sheet: meets UL 2034 and is rated 40–100 °F for living areas. It goes in the house outside sleeping areas (IRC 2021 R315), not in an unheated garage. Source ↗

Related

Sources

  1. [1] Electric Power Monthly, Table 5.6.B, average retail price by state, US Energy Information Administration. Retrieved 2026-09-25.
  2. [2] Natural gas residential price by state, annual, US Energy Information Administration. Retrieved 2026-09-25.
  3. [3] Weekly heating oil and propane prices, residential, US Energy Information Administration. Retrieved 2026-09-25.
  4. [4] On-highway diesel prices by PADD, US Energy Information Administration. Retrieved 2026-09-25.
  5. [5] International Fuel Gas Code, 2021, ICC. Retrieved 2026-09-25.
  6. [6] Dr. Infrared Heater DR-975 owner's manual, Dr. Infrared Heater. Retrieved 2026-09-30.
  7. [7] Mr. Heater MHU50 / MHU80 / MHU125 operating instructions and owner's manual, Enerco Group (Mr. Heater). Retrieved 2026-09-30.
  8. [8] Kidde C3010 sealed battery carbon monoxide alarm data sheet, Kidde. Retrieved 2026-09-30.
Size my garage — 60 s