We won’t print a fake ‘$0.47 per hour!’ figure, gas rates move, units differ, and your bill deserves your numbers. What we can give you is the two-minute calculation and the factors that bend it, which beats any stale table.
The formula
Hourly cost = (unit BTU input ÷ 100,000) × your price per therm. The BTU input is on the rating plate or manual (typical range: 20,000-40,000 for inserts and built-ins; gas log sets often higher). One therm = 100,000 BTU. Your per-therm price is on your Atmos Energy bill, take the total charged divided by therms used to capture delivery charges honestly, not just the commodity line.
Worked example, symbolically: a 30,000 BTU unit burns 0.3 therms/hour. At whatever your all-in therm cost is, three evening hours a few nights a week lands in single-digit dollars per week for most North Texas households, ambiance is cheap. Run it as primary heat eight hours daily and multiply accordingly, that’s where bills notice.
The factors that bend the math
Efficiency decides heat-per-therm. A sealed
direct-vent insert (70-85% efficient) delivers most of each therm as room heat; open vented gas logs send the majority up the flue, same hourly gas cost, wildly different warmth purchased
Zone heating flips the ledger. Heating the one room you occupy while the furnace idles lower can reduce total winter costs, the fireplace as savings, not spend, in DFW’s mild-winter pattern
Turndown and pilots. Variable-flame settings drop consumption near-linearly; standing pilots sip gas around the clock (electronic ignition ends that), worth checking on
annual service
The comparison shoppers actually want: per useful BTU delivered into the room, at typical regional prices, sealed gas units and heat-pump electricity trade the lead depending on rates, open gas logs trail badly, and wood is cheapest-or-priciest depending entirely on your fuel source. If running cost drives your decision, say so at the showroom stage, it points straight at high-efficiency sealed units.
We’ll spec accordingly.