What Actually Heats and Cools a Tiny Home

A backyard studio is a lovely idea in April. The test comes in late July, when it's 101 degrees outside and you find out whether the box you bought is a home office or a greenhouse.

This is the part of the build people underestimate most, and it's also where the biggest single purchase usually lands. So let's go through what actually works in a small structure, what to size, and the two things I'd genuinely avoid.

Start with insulation, not equipment

I know that's not the exciting answer, but it's the one that saves money. A well-insulated 200-square-foot studio can be comfortable on a fraction of the equipment a poorly insulated one needs, and insulation is a one-time cost with no running bill attached.

Most prefab sheds and kits ship uninsulated. The walls are sheathing and siding with an empty cavity behind them, which in an Oklahoma August is functionally a solar oven. If you're converting a shed into usable space, budget for insulation before you budget for a mini-split — and pay particular attention to the roof, where the heat gain is worst.

The main options, honestly compared

Ductless mini-split — the default

For most people in most tiny homes, this is the answer. One outdoor compressor, one indoor head mounted high on a wall, connected by a small line set through a three-inch hole. It heats and cools from the same unit, runs on a single circuit, and modern units are dramatically more efficient than anything else on this list.

The sizing rule for our climate, roughly:

• 9,000 BTU — up to about 350–400 sq ft, well insulated
• 12,000 BTU — 400–550 sq ft, or a smaller space with weak insulation
• 18,000 BTU — 550–800 sq ft, or a space with a lot of glass

Resist the urge to oversize. An oversized unit short-cycles: it blasts cold air, hits the setpoint fast, shuts off, and never runs long enough to pull humidity out. You end up with a space that's cold and clammy, which in a July in Oklahoma is its own kind of miserable. Correctly sized equipment running longer cycles is more comfortable and cheaper.

One more thing worth checking: if you want heat from it in winter, look at the rated heating range, not just the BTU number. Some units lose most of their heating capacity below freezing, which matters here in January even though it doesn't matter in June.

Window AC and a space heater — the budget path

There's no shame in this route, especially if the structure is a workshop or a seasonal studio rather than a full-time home. A window unit plus a good electric heater costs a fraction of a mini-split and requires no installation skill at all.

The tradeoffs are real though. You lose a window, the noise is significant in a small room, the efficiency is worse so your running cost is higher, and you're maintaining two devices instead of one. Over a few years, the efficiency gap can close much of the upfront price difference.

If you go this way, get an inverter-style window unit if you can. They cost more than the basic ones but run quieter and cycle far less abruptly, which matters a lot when the unit is eight feet from your desk.

Wood stove — heat with character

A small wood stove is genuinely excellent heat, works with no electricity at all, and is the thing that makes a tiny cabin feel like a cabin rather than a room. It's also the option with the most requirements attached.

You need clearance to combustibles on every side, a proper insulated flue through the roof, a non-combustible hearth pad underneath, and enough thermal mass in the room that you're not roasting within ten minutes. That last one catches people out — a stove sized for a normal room will make 200 square feet unbearable. Look specifically for stoves marketed for small cabins or boats.

Also worth knowing before you commit: adding a wood stove can affect your insurance, and some jurisdictions want it inspected. Worth a phone call before you cut a hole in your roof.

Two things I'd avoid

Portable AC units. They're the easiest install and the worst performer. Single-hose models pull conditioned air out of the room and exhaust it, which pulls hot outside air in through every gap to replace it — you're fighting yourself. They also take up floor space, which in a tiny home is the most expensive thing you own. If a window unit is physically possible, use one instead.

Unvented propane heaters indoors. These get recommended constantly in tiny home forums and they make me nervous. Unvented combustion puts water vapor and combustion byproducts into a very small sealed space. You get condensation problems at best and carbon monoxide at worst. If you're using propane heat, use a vented unit, and put a CO detector in the space regardless of what you heat with.

What I'd do

If it's a full-time space and the budget allows: insulate properly, then install a right-sized mini-split. That combination handles an Oklahoma summer and an Oklahoma January from one unit, and the efficiency means the running cost stays sane.

If it's a workshop, a seasonal studio, or you're staging the build across a couple of years: insulate first anyway, then start with a good window unit and a decent electric heater. You can always upgrade to a mini-split later, and the insulation you did up front makes that unit smaller and cheaper when you get there.

What I wouldn't do is buy the equipment before the insulation. That's the order that costs people money twice.

Related reading: How to Furnish a Tiny Home: What to Buy First · Do You Need a Permit for a Tiny House in Your Backyard?

Sizing figures here are general guidance for a hot-summer, mild-winter climate, not a substitute for a load calculation. Any electrical, gas, or flue work should meet local code — and in most places that means a licensed installer and an inspection.