Best mini split for a garage shop

The honest answer depends on three things: how many hours you use the shop, how cold it gets and how well the bay holds heat. If you work in the garage a few cold weekends a year, a small heater and a jacket cost the least. If you work there every week through the winter, the cost of staying warm is the largest ongoing cost of the shop, and the tool that makes the biggest difference to how much you use it.

The way to decide is to put numbers on it. Start with the garage heater BTU calculator, which estimates the heat your bay loses through its walls, ceiling and door. Then compare the cost of running a resistance heater with the cost of a heat pump. One watt of electric heat is 3.412 BTU per hour, so a 3750W resistance heater gives 12,800 BTU for 3750W of power. A heat pump delivers its rated heat from a fraction of that power, with the exact ratio on the listing and depending on the outdoor temperature. That ratio is the reason a heat pump can be cheaper to run, even if it costs more to buy.

This page was researched from manufacturer listings, published specifications and owner reviews. We do not give an operating cost in dollars, because it depends on your electric rate, climate and use. Plug your own rate into the calculator.

A space heater is cheap to buy and costs more to run. A mini split is expensive to buy and costs less to run. Beyond the cost, they differ in kind.

• Heat and cooling: a mini split heats and cools. A heater only heats. If you want a garage that is livable in midsummer, only the mini split does it. The mini-split cooling calculator sizes it.
• Install: a heater plugs in or hard-wires to a 240V circuit. A DIY mini split needs a wall hole, a line set, a condenser outside and a circuit. It is more work, and the lines and wiring are rules-based.
• Floor: neither takes floor. The mini split indoor unit hangs high on the wall, and the outdoor unit sits outside.
• Safety: neither burns fuel, which makes them better than gas in a shop with a car, fuel and dust.
• Cold weather: heat pumps lose output as it gets colder. Read the low-ambient rating on the listing.

The companion page, best garage workshop heater, covers the heater side, and you can read both and decide. If you only need heat now and then, buy the heater. If you need comfort all year, buy the mini split.

Mini splits come in sizes by BTU: 9,000, 12,000, 18,000 and up. A 12,000 BTU unit is one ton of cooling. For a garage, the right size depends on the area, the ceiling height, the insulation and the door. A sealed, insulated 12 x 20 ft one-car bay may need less than 12,000 BTU; an uninsulated 24 x 24 ft bay with a big door may need more. The sizing pages show the numbers for each bay: 12 x 20, 12 x 22, 20 x 20, 22 x 22, 24 x 24 and 32 x 24.

Do not oversize. A unit that is too big for the space cycles on and off, wastes energy and dries poorly. Do not undersize either. The calculator labels every constant as a CONVENTION, so you can see what was assumed and change it for your climate. Then look at the listing for the unit heating capacity at your design temperature, not just the cooling number on the box.

The first move for any bay is to cut the load. Insulate the door with a kit like the NASA TECH two-car kit, seal the gaps, and add insulation to the ceiling if you have an unfinished attic space above. A smaller unit on a tight bay beats a bigger unit on a leaky one.

The Albott and MRCOOL units are listed as 115V, which is why they suit a garage with no 240V. Check the nameplate for the minimum circuit ampacity and the maximum overcurrent protection; the listing and the manual give them. The usual answer is a dedicated 15 or 20 A circuit, with a disconnect near the outdoor unit as the code requires. Do not share the circuit with a saw, a compressor or a heater.

The wiring involves the indoor and outdoor units, a small control cable and the power feed. Some DIY kits ship with pre-charged line sets that you connect without special tools; follow the manual for that, and do not vent refrigerant. For the electrical part, have a licensed electrician confirm the circuit, breaker and disconnect against local code. A Klein clamp meter lets you check the real current draw once it is running.

If your garage already has a 240V circuit, a 240V mini split is another option, but the two units in our catalog are 115V. The 240V in a garage guide explains the choice.

High on a wall, away from the garage door and the car. A mini split indoor unit is typically 3 to 4 ft wide and about a foot deep; the listing gives the dimensions. It needs clear space around it for airflow and service. Do not hang it over a sanding station, where dust clogs the filter, or above a welding table, where spatter and smoke reach it. The outdoor unit sits outside on a pad or a bracket, with the line set running through the wall.

Aim the airflow along the length of the bay, not straight at the bench. Keep the drain line clear and sloped; it carries condensate out. Plan for the car: the line set and the pad should not interfere with the driveway or the door. In a shared bay, wall space is the premium, so locate the unit where it does not block pegboard or shelving, and see the tool storage page for how to use the rest of the wall.

Filters need cleaning, and a dusty shop clogs them fast. Check the filter monthly, and run an air cleaner as described on the air filtration page. If you cut wood, keep the unit as far from the saw as the bay allows.

A mini split in cooling mode removes moisture from the air, and many models have a dry mode for the purpose. Check your listing. A bay held at a steady temperature, with a sealed door and a mini split running now and then, has far less condensation on cold iron. That protects the table saw, the bandsaw and the vise from rust, which is a quiet cost of an unconditioned garage.

It will not replace a dehumidifier in a very damp bay. A stand-alone unit like the Frigidaire 50 pint is built for the job, and the dehumidifier page covers it. Many shops use both: the mini split for comfort, the dehumidifier for the damp months.

Keep a fire extinguisher by the door and a smoke alarm in the bay. This page gives general information, not HVAC or electrical advice. Ask a licensed professional about the installation, and check your local rules before you cut a hole in the wall.