Keystone · Model KSTHW12B
12,000 BTU Window Air Conditioner w/ Heat
A window air conditioner rated at 12,000 BTU for rooms up to 550 sq ft. It heats in winter too and self-installs in a window.
$499.99
Live price at SylvanePrice checked Sep 27, 2026
Performance
- Cooling capacity
- 12,000 BTU · 3.5 kW
- Heating capacity
- 11,000 BTU
- Room coverage
- up to 550 sq ft
- Energy Star
- Not published
- CEER
- Not published
- Annual energy (cooling)
- Not published
Noise, size & features
- Model number
- KSTHW12B
- Indoor noise
- 54.7 dB(A)about as loud as a dishwasher
- Outdoor noise
- Not published
Warranty, heating capacity and refrigerant are from Sylvane's published specifications for this exact configuration, checked Sep 26, 2026.
What is good
- Heats as well as cools, which 29 of the 155 window units we list offer.
- Uses R-32 (GWP 675), the low-GWP class new US residential equipment moved to.
Installation & the rules that apply
This is a window unit. No EPA Section 608 technician is needed: the refrigerant circuit is factory-sealed and never opened. A plug-in window unit needs no permit, so the friction is with your building rather than the government. Many HOAs restrict window units on appearance grounds, though an HOA regulating how you mount one stands on much firmer ground than one banning cooling outright. Landlords can set conditions, and the falling hazard is taken seriously: New York City, for instance, requires window units to be supported by brackets or mounting rails, and many building insurers and HOAs now require a bracket regardless of city.
Self-fit, no pro needed
R-32
Common questions about the Keystone 12,000 BTU Window Air Conditioner w/ Heat
- How loud is the Keystone 12,000 BTU Window Air Conditioner w/ Heat?
- 54.7 dB(A) indoors, about as loud as a dishwasher.
- What size room does the Keystone 12,000 BTU Window Air Conditioner w/ Heat cool?
- It is rated to cool a room up to 550 sq ft (12,000 BTU · 3.5 kW).
- Do I need a professional to install the Keystone 12,000 BTU Window Air Conditioner w/ Heat?
- No. It is a window unit you can fit yourself, no professional needed. Usually no permit.
- Does the Keystone 12,000 BTU Window Air Conditioner w/ Heat heat as well as cool?
- Yes. It also heats, rated 11,000 BTU of heating output.
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