The population was 2,316 on 1 January 2011.
The surrounding area is part of the Hengill central volcano, and is geothermally active and experiences very frequent (usually minor) earthquakes.
The town is known for its greenhouses, which are heated by hot water from volcanic hot springs.
The borehole Leppalúði on
the way to the Gufudalur valley erupts continuously, reaching a height of 10–12 meters. Close to the church is a hot spring called Sandhólshver, formed during the violent South Iceland earthquake of 1896. A fenced-off geothermal area in the town has numerous hot springs and fumaroles.
Hveragerði contains a number of greenhouses and is a hotbed for Icelandic horticulture.