Tuesday, December 2, 2025

can you explain why the U.S. uses 110 and 220 as the basis of electricity for homes?

 You learn something new every day. I wasn't aware for example that we had switched to 120 volts from 110 volts or from 220 volts to 240 volts so this was news to me. My question might be: "How does everything old do on the new higher voltages and could this result in more electrical fires?"

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The U.S. uses 110-120V and 220-240V for homes due to a combination of historical, safety, and efficiency factors, with the lower voltage being a legacy from early incandescent lighting technology and a safety choice, while the higher voltage is used for large appliances. Early American electrical systems, pioneered by Thomas Edison, operated at around 110V due to safety concerns and the limits of early carbon filament lamps. The 220-240V standard, which is more efficient for high-power devices, arose in other countries where they prioritized reducing wiring costs by doubling the voltage, which halves the current required for the same amount of power. 
Historical and safety reasons
  • Early electrical systems: The 110V standard was established early in the development of electricity in the U.S., partly due to a government-mandated safety limit of 100V, with Edison setting his standard at 110V.
  • Safety: Lower voltages are considered safer for household use, as they carry a lower risk of fatal electric shock compared to higher voltages. This was particularly important during the initial rollout of electricity in homes.
  • Legacy infrastructure: The U.S. invested heavily in 110V infrastructure, and the cost of changing all the existing appliances and wiring across the country made a switch to a higher voltage impractical and prohibitively expensive. 

Efficiency and convenience
  • Appliance types: Modern U.S. homes use a split-phase system, which provides both 120V and 240V power. 120V is used for standard outlets for electronics, lighting, and smaller appliances.
  • High-power appliances: 240V circuits are used for high-power appliances like electric dryers, stoves, and water heaters. This is more efficient for these devices and requires thicker, more robust wiring.
  • Transformer efficiency: The efficiency of power transmission and conversion is also a factor. While higher voltage is more efficient for long-distance transmission, 120V can be more efficient for some modern electronics, as it requires less voltage conversion to get to the lower DC voltages used by many electronic devices. 

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