We took a look at a ventless air-conditioner recently for windowless rooms, but if you do have windows for external venting but no landlord approval for a fixed installation – this model can be easily wheeled in to cool things down. Called the Best Portable Air Conditioner as it cooled three times faster and more quietly than competing models in testing, it produces a powerful 12,000 BTU to quickly and efficiently cool rooms as large as 400 square feet. With an easy-mount exhaust system that simply rests between a sill and an open window, the Best Portable Air Conditioner comes with 4 caster wheels for easy rolling between rooms, a washable air filter for consistently cleaner air and is available now from Hammacher Schlemmer for $599.95.