Why did old CRT monitors consume so much electricity?

The electron gun that shoots the electron beam at the screen at really high voltage, that's where it guzzles all the energy. You really gotta accelerate those electrons so they can travel through the tube and hit the phosphor hard enough to create light, so the old power supplies had to be massive and consume a lot of juice. Add to that there was basically no smart regulation of the energy flow like we have now with LEDs, and a big CRT is basically just a huge box of plastic and glass that needs cooling, that's why your electricity bill shot up.

It's also because CRTs had to constantly refresh the image by sweeping the beam across the entire screen surface several times a second - so it wasn't just a one-time voltage thing, but continuous, very intensive work. Add to that the fact that these old monitors lost a lot of energy as heat 🔥, and you understand why your electricity bill would shoot up with one of these things running 8 hours a day.

The cathode ray tube had to maintain an almost-perfect vacuum inside, and it was the pump that created and maintained that vacuum that was eating up a good chunk of energy continuously - not just the electron gun. Add to that the fact that the high-voltage power supply was inefficient compared to what we can do now, no sophisticated digital converters to optimize power consumption. If you want to compare with modern equipment, an old 17-inch CRT monitor easily drew 50 - 70 watts just to operate, whereas an LCD screen the same size today uses more like 15 - 20 watts.

You've probably never noticed how hot an old CRT would get after a few hours? That's because all that current flowing through the deflection circuits (the coils that guided the beam horizontally and vertically) generated a ton of waste heat. Other explanations talk about the electron gun and the vacuum, but honestly the power consumption also came a lot from the overall power supply that had to provide really unstable voltages and significant currents constantly - not just to accelerate the electrons, but for all the control circuits around the tube 🔥