Wind and solar cannot replace coal, oil and gas as the world’s power workhorse. It's because of the physics, the slogans and empty promises. 'Renewables' are built from costly and high-maintenance, low-yield technologies. They degrade from the day one and do not run when needed. Wind and solar harnessing devices are intermittent by their nature. They do not deliver baseload power. Whether they have delivered a net public return on the subsidies that built them, is a separate accounting issue; but the machines themselves do not. They are not simple to build either. They are highly complex arrays of electronics, specialised glass, composite blades and concrete. Like any appliance, they wear out. For many early rooftop buyers, that has already happened: their panels are now roof junk. A wind turbine cannot take all the energy out of the air that passes by. In 1919 Albert Betz showed why: if the blades extracted 100 percent of wind’s kinetic energy, the air behind them would stop, and new wind could not enter. The theoretical maximum for an open-flow turbine is 59.3 percent. In the field, good machines reach about 45 percent, but only in ideal wind conditions. Over a year, global capacity factors sit roughly in the mid-20s to high-30s, depending on site. It's a built-in mechanical bottleneck. Solar also hits a wall of its own. Standard silicon cells sit under the Shockley–Queisser limit of about 33 percent. Much of the incoming spectrum is either too energetic and is lost as heat, or too weak and passes through unused. Nameplate claims of 'clean power from the skies' do not change this energy loss. Commercial arrays lose energy from the angle of the sun, dirt, heat and failing inverters. Rooftop capacity factors are often around 12–15 percent; commercial solar sits higher, but still far below promised production levels. Because they only work 'sometimes', they need a second backup system, because they were not designed to integrate into the existing grid as dispatchable power. So to compensate, they created more wires, more backup gas and short-lived battery arrays. On a net-zero path, BloombergNEF has put the global grid-upgrade bill at about $21 trillion by 2050. That is the price of redundant machines that cannot hold the load on their own.Homeowners discovered the rest. Rooftop solar does not start a washing machine or a dryer after dark. As early subsidies and high feed-in tariffs fade, owners keep paying daily grid charges while output falls. Solar panels are warrantied for decades; but the string inverters are not. Ten to fifteen years is a common solar lifespan. When it dies, power generation stops. What remains on the roof is expensive silent hardware. They promised power from wind and sunlight. But the physics never allowed it.