This example presents a reusable D3 v7 area chart showing 24 months of synthetic household electricity usage in kWh, with the filled area emphasizing magnitude relative to a zero baseline. It renders an SVG with a gradient-styled area, an overlaid line, dots, axes, gridlines, and a hover tooltip that displays exact values. The chart uses d3.area, d3.line, d3.scaleTime, d3.scaleLinear, and d3.axisBottom/axisLeft, and supports updates via a public update method that redraws the visualization with new data.