3. Determine the system size and assess the need for supplemental heating

Sizing a system involves determining the technical and economic optimum of the resource-production system based on the site’s thermal requirements (for heat and, if applicable, cooling). To represent these requirements, a demand curve must be plotted, as shown in Figure 1 for heating requirements. This demand curve can be supplemented by a load curve, as shown in Figure 2, which represents heating requirements and the number of hours associated with these requirements for different types of spaces: as can be seen, these demand curves are highly dependent on the building’s energy performance, the quality of its insulation, its airtightness, and, of course, local weather conditions.