Why do renewable energy sources require some form of energy storage or backup?

• A. Because they are intermittent (e.g., sun doesn’t shine at night; wind variability).
• B. Because they produce constant energy.
• C. Because they are too expensive.
• D. Because they don't require maintenance.

Answer: (A)

Renewables are variable because their output depends on weather and time of day, not a constant fuel source. To keep electricity reliably available as demand changes, we need some form of storage or backup. Storage—like batteries or pumped hydro—saves excess energy when production is high (bright sun, windy periods) and releases it when production drops (nighttime or calm weather), helping to smooth out the supply. Backup generation, such as fast-responding power plants, can quickly fill in gaps to maintain steady grid operation. This balancing is essential for reliability, since the grid needs a relatively steady supply even as renewable output fluctuates. The other choices don’t fit: energy from renewables isn’t constant, cost isn’t the fundamental reason storage is used, and maintenance needs aren’t the reason storage and backup are required.