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Electricity Basics

What Is Electricity?

Electricity is the flow of electrons through a conductor (like a wire). Electrons are tiny particles inside atoms. When something causes them to move in the same direction, we have an electric current.

Think of it like water in a pipe: - Voltage (V) = water pressure — how hard the electrons are pushed - Current (A) = water flow rate — how many electrons are moving - Resistance (Ω) = pipe width — how hard it is for electrons to flow

DC vs. AC

DC — Direct Current Electrons flow in one direction. Batteries produce DC. Solar panels produce DC.

AC — Alternating Current Electrons flow back and forth rapidly (60 times per second in the US). The power coming out of your wall outlets is AC. AC travels efficiently over long distances, which is why the power grid uses it.

The Power Formula

Power = Voltage × Current

P (watts) = V (volts) × I (amps)

Examples: - A 120V outlet with 10A of current = 1,200 watts = 1.2 kW - A 400W solar panel at 40V produces 10 amps in full sun

Energy vs. Power

  • Power (W or kW) = rate of energy use right now
  • Energy (kWh) = total energy used over time

A 1,000W (1 kW) appliance running for 1 hour uses 1 kilowatt-hour (kWh) of energy.

Your electric bill charges you by the kilowatt-hour.

Why Does This Matter for Solar?

Solar panels produce power (watts). Your home uses energy (kilowatt-hours). A solar system is sized to match how much energy you use. Understanding the difference between power and energy is the first step to understanding solar system design.