Meet Sam’s 300-Sq-Ft Cabin on Wheels
Sam just bought a cedar-clad tiny house, 24 ft long and 8 ft wide, bound for the sunny Texas Hill Country. It smells like fresh lumber now, but summer is coming—and so is the heat. Sam’s first question: “What size HVAC keeps me cool without eating my battery bank?” We’ll solve that puzzle together, step by step, using the same field math pros use every day.
Measure the Conditioned Area, Not Just the Floor
Grab a tape measure and multiply the interior length × width to get square footage. Stop when you hit walls that won’t be cooled (storage lofts, unconditioned porches). Sam’s cabin: 24 ft × 8 ft = 192 sq ft. At 20–30 BTU per square foot, his starting range is 3,800–5,800 BTU.
Write the number on painter’s tape and stick it to the fuse box. You’ll reference it often.
Count the Heat Leaks Insulation & Windows
R-10 spray foam? Add nothing. R-7 fiberglass? Increase capacity by 10 %. Large single-pane windows? Add another 10 % if glass covers more than 25 % of the walls. Sam’s south-facing picture window bumps him to roughly 6,300 BTU.
Quick checklist
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Insulation rating (walls, floor, roof)
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Window area and glazing type
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Door seals tiny gaps add up
Need better windows? The Furnace Outlet’s Help Center explains low-E glass in plain English.
Think in BTUs, Not Tons
Big houses talk in half-tons; tiny homes live in hundreds of BTUs. Round Sam’s adjusted 6,300 BTU upward to the nearest unit size. 9,000 BTU mini-splits are common. Going smaller (6 k-BTU) risks cooking on 105 °F days; going larger (12 k-BTU) invites short-cycling. Keep your math honest and your comfort steady.
Why Oversizing Wreaks Havoc in Small Homes
A system that’s too powerful cools fast, shuts off, and leaves humidity behind. You feel sticky, the unit guzzles energy, and mold loves the moisture. Undersize it and you’ll listen to a fan that never quits. Aim for the Goldilocks zone by sticking within 10 % of your calculated load.
Use the free calculator in the Furnace Outlet Design Center to sanity-check your numbers.
Mini-Splits: The Tiny-Home Workhorse
Wall-mounted ductless mini-splits pack heating and cooling into a shoebox-size indoor head. Sam chose a 9 k-BTU R-32 model from our DIY line, no big ducts, no attic space wasted.
Why they shine:
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High SEER ratings (20 +) slash utility bills.
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Variable speed compressors sip power on mild days.
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Whisper-quiet is great for studio layouts.
Need one fast? Browse ductless mini-splits in stock today.
Heat Pumps: Four-Season Comfort on Wheels
Live where winters bite? Pair that mini-split with an R-32 heat-pump condenser for toasty nights down to 5 °F. Heat pumps move heat; they don’t burn it, making them 3× more efficient than electric strip heaters. Check out our R-32 heat-pump systems for plug-and-play packages that fit 30-amp service panels.
Window & Portable Units When “Good Enough” Works
On a shoestring? A window AC cools one room for under $400. Stick to EnergyStar models around 5–6 k-BTU for < 200 sq ft. Portable AC/heaters roll anywhere but need a vent hose and chew more watts. For rentals or weekend cabins, browse room ACs—just remember to seal the side panels tight.
PTAC & VTAC: Hotel Tech for Tiny Lofts
Ever stayed in a quiet hotel room? That’s usually a PTAC humming behind the grille. These through-wall units deliver all-in-one heating and cooling with simple maintenance. Vertical versions (VTACs) hide in a closet, freeing wall space. Explore hotel-grade PTACs and VTAC units if floor plans limit wall mounts.
Compact Central Systems for Modular Builds
Building a 1,000 sq ft prefab? Small-duct, high-velocity systems like Unico push conditioned air through 2-inch flexible tubes. They tuck into joist bays and keep ceilings clean. Pair them with an R-32 air handler and a slim condenser for big-house comfort in a tight shell.
Power & Panel Checks Avoid Tripped Breakers
Tiny homes often run on 30-amp RV hookups or small solar arrays. Before ordering gear, open the panel:
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Match voltage (120 V vs 240 V).
- Check breaker count—mini-splits need a dedicated double-pole.
Confirm the wire gauge meets the unit’s MCA rating.Unsure? Our techs at Contact Us walk you through the math in minutes.
Your Action Plan: Right-Size, Install, Relax
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Measure conditioned space.
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Adjust for insulation, windows, ceilings, and climate.
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Pick the smallest unit that meets—but doesn’t exceed—your BTU target.
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Verify electrical capacity.
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Shop trusted gear: mini-splits, PTACs, or compact central kits at The Furnace Outlet.
