How do I size a solar-powered signalling site?

AS 7703 clause 4.2.3 sets the method: battery storage shall be calculated to ensure power is available for the total period required, accounting for the maximum contiguous cloudy days at that location, battery capacity degradation over service life, and availability and reliability calculations. In practice that means three things a generic solar calculation omits: use the worst-month solar resource for that latitude, size to end-of-life capacity rather than nameplate, and apply the temperature derating for the location case rather than for ambient. A site that only just meets its autonomy requirement when new will not meet it in year eight.