Abstract: The proposal is for a heater consisting of a container with connections for a heating agent circuit for the circulation of a heat conveying medium, in which the container (50, 59) through which the heat conveying medium is to flow is thermally connected to at least one heat store fitted in the heater and preferably in which the container (50, 59) is at least partially fitted in another container (51) of heat-conducting material which can be filled with a heat storage fluid, where the two containers are not in mutual fluid communication and/or the container (50,59) through which the heat conveying medium flows is at least partly adjacent to a solid heat storage core (20). The invention also relates to a heating installation with heaters of the invention making use of solar power.