Separate essential loads from flexible ones
Lighting, communications, water and refrigeration may have different priorities from laundry or work that can wait. List the minimum daily service and equipment that can operate on a restricted schedule. Adding every nameplate rating and multiplying by one running time does not describe real demand.
Check the seasonal energy balance
Solar resource, shading and seasons affect generation. After poor weather, the system must supply loads and recharge the battery. Generation sized only for an ordinary day can leave little recovery margin. Ask for low-generation operation, minimum energy rules and the recovery sequence, rather than an annual average alone.
Agree on backup arrangements early
If a generator remains, define starting, charge power, switching, protection, fuel and maintenance. Reducing flexible loads is another option worth comparing. The final design depends on site resources and the agreed service boundary. A promise of uninterrupted power without those conditions is not a useful specification.
Further reading: www.energy.gov
This article supports early project discussions. Final configuration depends on site conditions.