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 ; the core including a first outward side , a thermal mass , and an electric element arranged to heat the thermal mass ; respective surfaces 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 (P1) 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 (X1) 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 (X1) 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 are projected onto the convection plane (P1), the first protrusions are arranged in-between the second protrusions in the convection plane (P1) so that the convection space defines a serpentine flowpath between respective adjacent ones of the first and second protrusions ; and a perforation is formed in each recess base wall between the first and second sides of the pane! . the casing including a panel , the panel having opposite, first and second sides ; the core including a first outward side , a thermal mass , and an electric element arranged to heat the thermal mass ; respective surfaces 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 (P1) 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 (X1) 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 (X1) 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 are projected onto the convection plane (P1), the first protrusions are arranged in-between the second protrusions in the convection plane (P1) so that the convection space defines a serpentine flowpath between respective adjacent ones of the first and second protrusions ; and a perforation is formed in each recess base wall between the first and second sides of the pane! . <EOS>