Projectors make any home theater or work presentation a professional affair. We look at several factors that affect your purchase, from usage needs to technical specs.
Entertainment or Business?
The first thing to think about is the kind of content you want to show on the projector. Most business projectors are going to be used for a series of still images. If you're thinking about PowerPoint presentations and bar charts, then look in the business category. The home projector category is going to handle full motion video a lot better. If you want to play movies or games, make sure that your chosen projector can handle them.
Indoor vs. Outdoor
For the most part, if you want to use a projector outdoors, you need better quality all-round. You want the highest brightness, because you have less control over the ambient light, you want a high resolution and contrast ratio to boost your chances of a great picture, and you'll need a good screen or surface, and a decent sound system. One thing that might be more of a concern with an indoor projector is the noise it makes when operating, because that's going to be more noticeable in a small room, but beyond that a good outdoor projector will work well indoors too.
You should check out the reviews for your prospective projectors carefully and make sure that you get a reliable model. You'll often see a lamp life rating, estimating the maximum hours you'll get before needing to replace the bulb. Obviously the higher that is, the better your chances of it lasting a longer time. You should also check out the cost of replacement bulbs and other parts, and get an idea of how easy it will be to maintain and repair, should you need to.
If you're planning to install your projector in a fixed position, for something like a home theater, then you don't really have to worry about portability at all. If you plan on traveling around, using it for business presentations, then you'll want something that's as small as possible.
You could pick up a good quality, portable business projector for presentations, for as little as $300, but you should expect to pay a bit more if you want a decent range of features and quality. For home entertainment you should be ready to spend between $800 and $3,000 for a good projector. You can spend a lot more than that if you want the best. A good 4K projector could set you back $10,000 easily. Bear in mind that you'll want some money left for your screen and audio setup.