⚡ Residential Electricity Use and Cost Explorer

Understanding AC and DC Power

Electrical power, measured in watts (W), is calculated the same way for both AC (alternating current) and DC (direct current): Power = Voltage × Current

RMS (Root Mean Square) - The Key to AC Power

AC voltage constantly changes, but RMS voltage gives us an equivalent DC value that produces the same power. When we say "120V AC," we mean 120V RMS, which delivers the same power as 120V DC at the same current.

Common Voltages and Conversions

Power Conversion Devices

Inverters: Convert DC to AC (solar panels to home grid, EV to home backup)

Rectifiers: Convert AC to DC (EV charging, electronic devices)

Why convert? AC is efficient for long-distance transmission, while DC is better for electronic devices and battery storage.

Current Limits and Power Availability

At a fixed voltage, current determines available power. Most homes have:

• 120V circuits: 15-20 amperes → 1,800-2,400 watts maximum
• 240V circuits: 30-50 amperes → 7,200-12,000 watts maximum
• Main service: 100-200 amperes at 240V → 24,000-48,000 watts total

Circuit breakers prevent overloading by cutting power when current limits are exceeded.

Power vs. Energy: Watts vs. Kilowatt-hours

Power (Watts/Kilowatts): Rate of energy use at any moment

Energy (Kilowatt-hours): Total amount of energy consumed over time

Think of it like speed vs. distance: a 1,500W heater running for 2 hours uses 3 kWh of energy.

Electricity Costs in the United States

National Average: ~16 cents/kWh

Alabama Average: ~14.2 cents/kWh (below national average due to abundant hydroelectric and natural gas)

Electric utilities charge by energy consumed (kWh), not power capacity (kW), though some have demand charges for large users.