An electric firebox is the fireplace unit itself, designed to be framed into a wall, a mantel or a custom surround so it finishes flush with the surrounding material. It is what you choose when you want to create a fireplace in a room that does not have one, and it gives you full control over the surround, the materials and the final look.

A firebox builds a fireplace where none existed, by being framed into new construction or a custom enclosure. An insert fits into a masonry opening that is already there. If you are starting from a bare wall, you want a firebox. If you are converting an old wood burning fireplace, you want an insert.

Plug in models connect to a standard 120 volt outlet and are simpler to install, making them suitable for lighter framing and straightforward projects. Built in models are hardwired, run at 120, 208 or 240 volts depending on configuration, and deliver higher heat output. Hardwired units must be connected by a licensed electrician.

It varies by model and wiring. Plug in units on a 120 volt circuit typically deliver around 1500 watts, suited to a single room. Hardwired units offer staged output that can reach roughly 2575 watts at 240 volts, which covers a larger space. Check the specification on the model you are considering.

Yes, and that is the point of choosing a firebox. It is designed to be framed and finished with the materials you want, whether that is drywall, tile, stone or millwork. Follow the framing dimensions and the clearance to combustibles given in the instructions for your model, and keep the heater outlet unobstructed.