Those seats were not just for show.  They covered the cooling units that drew much of the 115 kilowatts of power the machine used to keep from melting.  Today the supercomputer in my pocket is about the size and shape of a candy bar.  It is far more powerful than the Cray -1, draws less than 1 watt of power most of the time and barely gets warm.  It pretends to be a telephone but is really a vast multifunction device with camera, GPS, internet access and other functionality all built in. My pocket phone was made possible by the exponential reduction is size and power of the integrated circuit.  The integrated circuits in the Cray-1 contained a few dozen to a few hundred transistors. The chips in my phone have billions of transistors. 

The same semiconductor technology that gave us the transistor, and its progeny the integrated circuit, also gave us the light emitting diode (LED).  LEDs are far more efficient at producing light than traditional lighting devices, especially the incandescent lamp.  And just like the solar cell it took many decades for LEDS to become cheap enough and powerful enough to be used for general lighting.  Today the LED lights in my office run on 6.5 watts of power.  They output the same amount of light that the 50 watt light bulbs used to produce.  In addition to using less power for the light I also eliminate the 44 watts of heat each incandescent light produced that I had to remove with air conditioning, a double savings that gives me a 10-15 fold reduction in total energy usage for the same amount of light. This is not the 100,000 to 1 reduction in power of my pocket supercomputer, but when you count all of the lightbulbs in my house the savings do add up. 

Computers and lights are not the only devices that have become more efficient.  Televisions and computer monitors have gone from Cathode Ray Tubes (CRTs) that used 100s of watts of power to Liquid Crystal Displays (LCDs) that run on 10s of watts.  Compressors in refrigerators and air conditioners are far more efficient. Furnaces burn their fuel more completely and houses, while bigger, are far better insulated and many have double or triple glazed windows.

So what does all of this efficiency have to do with solar power?  In the late 20th century one of the major arguments against renewable energy, besides cost, was that energy consumption was rising so fast that only by adding massive amounts of coal and nuclear power could we keep up with demand.  As the following graph shows energy demand in the U.S. has actually been flat since the beginning of the 21st century.