Today, in our environmental science lecture, we're discussing renewable energy sources. Solar power is increasingly popular, but it has a limitation: it only generates electricity during daylight hours. To address this, some households install battery storage systems, like the Tesla Powerwall, to store excess energy for nighttime use. However, these batteries are expensive, costing around $10,000. An alternative is net metering, where homeowners sell surplus electricity back to the grid during the day and buy it back at night, effectively using the grid as a battery. This approach is more cost-effective in many regions, though it depends on local utility policies.