A scalable solution can be increased or decreased in size and/or complexity with impunity. Cloud-based solutions can be scaled up and down according to requirements as an organisation expands or downsizes, because costs are charged on an operational basis and capacity is, for all intents and purposes, unlimited. CPE solutions can scale up, but only with limited flexibility because each model of PBX has a set maximum capacity. An organisation which needs 250 seats may be forced to choose between a 200-seater, insufficient to their needs, or a 500-seater, an over-engineered solution. And CPE solutions cannot scale down at all, because once the PBX is on-site, the capex has been paid and cannot be retrieved. That means that an organisation that is downsizing will end up with excessive capacity which is not being used. Scalability is almost always considered a desirable trait in an IT or telephony solution for any organisation, because it allows them to adapt to unforeseen events.