
MRCOOL
The MRCOOL DIY 5th Gen 36K is the largest single-zone DIY ductless heat pump, rated 18 SEER2 on R-454B and sized for very large rooms. It trades the higher efficiency of the smaller DIY units for raw 3-ton capacity.
$3,299
List priceHome Depot list price for the single-zone 36K complete DIY system, June 2026. Needs a 230V dedicated circuit.
This is a single split. This is where regulation bites. Under EPA Section 608 the refrigerant circuit may only be opened by a certified technician, and the EPA is explicit that this includes connecting or disconnecting the pre-charged line sets sold with "DIY" mini-split kits. No federal law stops you doing the mounting, bracketing and line routing yourself, but handling the refrigerant without certification voids the warranty and is a violation. Most US jurisdictions also require permits for a new outdoor unit: typically mechanical or building for the wall penetration and mount, plus electrical for the dedicated 240 V circuit and disconnect. An HOA nearly always has to approve exterior equipment in advance, and local noise ordinances can cap how loud the condenser may be at the property line. This varies by city and county, so confirm with your building department before buying hardware.
Plug and play
R-454B
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Will it cool your room?
This unit's cooling matches a 861 sq ft room. Set your room size to check the fit for your space.
Mini-splits are rated on SEER2, a seasonal scale, not the ENERGY STAR annual-kWh figure this dollar estimate is built from, so there is no comparable figure to show here. A blank is missing data, not a worse result: a mini-split is often the more efficient choice.
At a glance
Best for diy cooling and heating of very large single spaces.
$3,769
at Sylvane
+ pro install, usually $1,500-4,000