A wall mountable electric heater comprising a casing and a core arranged in the casing; the casing including a panel, the panel having opposite, first and second sides (40, 41); the core including a first outward side, a thermal mass, and an electric element arranged to heat the thermal mass; respective surfaces (47, 27') of the second side of the panel and the first outward side of the core being spaced apart in opposed relation on opposite sides of a nominal convection plane lying in a convection space between the panel and the core; characterised in that the first outward side of the core has a plurality of first protrusions, the first protrusions being spaced apart in two dimensions to form a spaced array; the panel having a plurality of recesses, the recesses being spaced apart in two dimensions to form a spaced array on the first side of the panel; each recess extending along a recess axis towards the first outward side of the core to define a second protrusion on the second side of the panel; each recess having a recess sidewall and a recess base wall, the recess sidewall surrounding the recess axis and extending towards the first outward side of the core and terminating at the recess base wall, the recess base wall being spaced apart from the first outward side of the core by a separation distance D1; wherein, when the first and second protrusions (26, 44) are projected onto the convection plane, the first protrusions are arranged in-between the second protrusions in the convection plane so that the convection space defines a serpentine flowpath between respective adjacent ones of the first and second protrusions (26, 44); and a perforation is formed in each recess base wall between the first and second sides (40, 41) of the pane!. the casing including a panel, the panel having opposite, first and second sides (40, 41); the core including a first outward side, a thermal mass, and an electric element arranged to heat the thermal mass; respective surfaces (47, 27') of the second side of the panel and the first outward side of the core being spaced apart in opposed relation on opposite sides of a nominal convection plane lying in a convection space between the panel and the core; characterised in that the first outward side of the core has a plurality of first protrusions, the first protrusions being spaced apart in two dimensions to form a spaced array; the panel having a plurality of recesses, the recesses being spaced apart in two dimensions to form a spaced array on the first side of the panel; each recess extending along a recess axis towards the first outward side of the core to define a second protrusion on the second side of the panel; each recess having a recess sidewall and a recess base wall, the recess sidewall surrounding the recess axis and extending towards the first outward side of the core and terminating at the recess base wall, the recess base wall being spaced apart from the first outward side of the core by a separation distance D1; wherein, when the first and second protrusions (26, 44) are projected onto the convection plane, the first protrusions are arranged in-between the second protrusions in the convection plane so that the convection space defines a serpentine flowpath between respective adjacent ones of the first and second protrusions (26, 44); and a perforation is formed in each recess base wall between the first and second sides (40, 41) of the pane!.