Final answer:
The primary difference between a stand-alone and a grid-connected PV system is that a stand-alone system must be sized with ample storage to cover energy needs during periods without sunlight, whereas a grid-connected system can rely on the electrical grid to supplement solar production.
Step-by-step explanation:
The fundamental difference between sizing a stand-alone PV system and a grid-connected system lies in their scaling requirements and dependence on external infrastructure. A stand-alone PV system, also known as an off-grid system, requires sufficient sizing to accommodate for periods when solar energy is not available. It must be capable of meeting the energy needs through local storage solutions, like batteries, to ensure a constant supply of electricity despite the intermittency of solar production.
In contrast, a grid-connected system is connected to the local electrical utility grid, thus allowing for energy exchange. It can export excess solar production during the day and draw from the grid when production is insufficient, particularly at night or when demand exceeds solar production. This means that a grid-connected system may not require as extensive local storage, which can reduce initial costs and complexity. However, grid-tied systems cannot provide power during outages unless they incorporate a form of backup power like a battery with a grid-interactive inverter.