In English
Nothing is filled in yet.
Pick a fuel, a heater, and a room size. The burn time, cost, and sizing show up here once those boxes have numbers.
Residential efficiency analyzer
How much gas will it actually burn?
Pick the heater, the room, and the weather. We’ll tell you — in English — how long a gallon of propane lasts, what a therm of natural gas gets you, and whether that 32,000 BTU unit is a match or a waste.
Weather waits on a room size.
Outdoor temperature only matters once length, width, and ceiling are in.
Draft clinic
Cheap fixes before a bigger burner
Most “the heater isn’t enough” calls are a door, a hatch, or a garage seal. Look here first.
Outlet and switch gaskets
an hour · under $20
Look for: Exterior walls, especially behind the couch and at the thermostat. The plate will be cold, or a tissue will flutter.
Do this: Kill the breaker. Foam gaskets go under the cover plate. Child-safety plugs in unused receptacles on outside walls. It is unglamorous and it works.
Sashes that don’t actually latch
an hour · scrap / tape
Look for: Old double-hungs. The lock is decorative and the meeting rail has a gap you can see through.
Do this: Latch both locks. A sprung sash gets a cheap window wedge. Interior film kits on the worst panes for winter — ugly, effective, reversible in April.
The attic hatch is a chimney
an afternoon · under $60
Look for: Pull the hatch. If there’s no rigid foam on the back and no weatherstrip on the stop, you’re heating the attic.
Do this: Glue 2-inch foam to the back of the lid. Weatherstrip the stop. A store-bought hatch tent is fine if you don’t want to build a box.
Fireplace damper that’s ‘closed’
an hour · under $60
Look for: Hold a lit incense stick at the opening with the damper ‘shut’. Smoke going up is money going up.
Do this: A chimney balloon or a snug-fit damper plug for the season. Glass doors help only if they actually latch. Never block a gas log that isn’t listed for it.
Old recessed lights
an afternoon · under $150
Look for: Six-inch cans in a room under an attic. They are little chimneys. Dust rings on the trim are a clue.
Do this: ICAT-rated LED retrofits that seal the hole. Don’t bury a non-IC can in insulation. If there are a dozen of them, this is one of the highest-payback afternoon jobs in an older house.
Interior storm film on the worst glass
an afternoon · under $20
Look for: Single-pane, metal sliders, or a sunroom that feels like the outdoors with furniture.
Do this: The shrink-film kits work if you clean the paint and give the hair dryer a minute. Do the north and west glass first. It looks like a greenhouse. It also cuts the load a vent-free unit is fighting.
Crawlspace vents in January
an hour · under $20
Look for: Open foundation vents with a heater running upstairs. You’re conditioning the neighborhood.
Do this: Foam-board plugs or magnetic covers for the heating season, then take them out in late spring if the space needs to dry. A chronically wet crawl is a different job — don’t seal a swamp.
The return that’s sucking from the attic
an afternoon · under $60
Look for: Filter slot that doesn’t latch, panned joist returns, or a filter gray on one side and the house still dusty.
Do this: Mastic or foil tape (not cloth duct tape) on every joint you can reach. A tight filter rack. If the unit is in the garage or attic, leaks there pull fumes and insulation into the house.
Shop notes
Useful facts
A gallon of propane is 91,500 BTU
That’s the number we use on the bench. A therm of natural gas is 100,000 BTU, so they are close cousins. Divide the fuel by the nameplate and you get hours on high. A 32,000 BTU vent-free heater: about three hours a gallon, about three hours a therm.
Nameplate is input, not what the room gets
Vent-free is basically 100% — the heat has nowhere else to go. An 80% direct-vent 30,000 BTU unit puts about 24,000 into the room. A 96% furnace does what it says. Always size on output.
Charlotte design winter is about 20°F
We heat to 70. That’s a 50° gap. A 40° afternoon is a much smaller job than a 18° Tuesday at 6 a.m. If a garage ‘never catches up’, look at the door and the uninsulated walls before you buy a bigger burner.
Garages lose heat through the door, not the heater
A two-car door is a wall that moves. No bottom seal, no insulated panels, and a 32k heater will run its heart out. Seal, then size. Heating an uninsulated garage to 70 all winter is how tanks go empty on a Thursday.
Vent-free makes water
Burn a gallon of propane and you put about 0.8 gallons of water into the air. Tight houses show it on the windows first. That’s chemistry, not a defective unit. Direct-vent throws the water outside with the exhaust.
ODS and CO alarms are not optional
Every vent-free unit has an oxygen depletion sensor. Don’t bypass it. Put a carbon monoxide alarm in the space, not in a drawer. Yellow flame, soot, or headaches — shut it down.
Tankless cares about incoming water temperature
City water in Charlotte in January is often the low 50s. A 105° shower is a 50°+ rise. Two 2.2 GPM showers is 4.4 gallons a minute. Run the numbers before you believe the ‘whole house’ sticker.
Turning it down beats a bigger unit
Most vent-free and DV heaters have a low setting around half input. Twice the hours on the same gallon. A $20 plug-in thermostat on a millivolt unit (if the unit allows it) is the cheapest efficiency upgrade in the catalog.
This is shop math, not a Manual J
A full load calc wants windows, orientation, infiltration, and duct losses. This tool is here so a customer can see — in English — that a 32k heater is a lot of fire for a 12×16 bedroom, and not enough for a naked two-car garage. When the house is weird, we measure it.
Tip jar
If this saved you a wasted service call
HandyGas Heat Check is free for customers. Tips go to the shop via Square.
Open the Square tip jarhttps://square.link/u/jIRR3rhz