What the Numbers Mean

With the defaults (500 W → 200 W, 4 hrs/day, $0.15/kWh, $800 purchase), the old appliance costs $109.50/year to run and the new one $43.80 — saving $65.70 annually. The $800 appliance pays for itself in about 12.2 years, so it only makes sense for appliances near the end of life or with heavy usage.

When Upgrades Win

High-usage appliances are the best candidates: a refrigerator runs 24/7 and an electric water heater or dryer runs hot, so even modest wattage cuts produce large annual savings. For lightly used devices, the payback can exceed the appliance's lifespan.