Solar, wire sizing, and electrical
Three tools for the most code-regulated category. Electrical sizing references NEC tables because the consequences of undersizing are severe.
Electrical calculations are safety calculations
Undersized wire overheats under load. Overheated wire melts insulation. Melted insulation starts fires. This is not hypothetical — the National Electrical Code (NEC) exists because the consequences of electrical undersizing are severe. Every wire gauge, every circuit breaker rating, and every extension cord capacity is specified by code because getting it wrong can burn down a house.
Wire sizing: NEC Table 310.16
The wire size calculator looks up the correct AWG gauge for any circuit based on amperage, wire material (copper or aluminum), and run distance. It also checks voltage drop, which NEC recommends keeping below 3 percent on branch circuits and 5 percent total (feeder plus branch). Long wire runs over 50 feet often require upsizing by one or two gauges to stay within the voltage drop limit. The common residential gauges are 14 AWG (15-amp lighting circuits), 12 AWG (20-amp general outlets), 10 AWG (30-amp dryer and water heater), and 6 AWG (55-amp sub-panel feeders and EV chargers).
Extension cords: temporary wiring with permanent consequences
Extension cord fires cause an estimated 3,300 home fires per year in the US. Nearly all are caused by using an undersized cord for the load, daisy-chaining multiple cords, or running a cord under a rug where heat cannot dissipate. The extension cord calculator sizes the correct gauge based on your tool's amperage draw and the cord length. A 16 AWG cord is fine for a lamp but dangerous for a table saw. A 100-foot 16 AWG cord at full load drops voltage by 8 percent — enough to damage a motor permanently. The calculator flags these situations before you plug in.
Solar: sizing starts with your electric bill
The solar calculator sizes a solar array based on your monthly kWh usage and your location's peak sun hours. Phoenix gets 6 to 7 peak sun hours per day. Seattle gets 3.5 to 4. The same house uses the same electricity, but Phoenix needs 40 percent fewer panels to produce the same energy. System cost runs $2.50 to $3.50 per watt installed before the federal Investment Tax Credit (ITC).
The 30 percent federal ITC applies to all solar installations through 2032, reducing net cost by nearly a third. A $18,000 system becomes $12,600 after the credit. Many states add their own rebates on top. Payback periods range from 4 to 6 years in high-electricity states (California, New York, Connecticut) to 10 to 14 years in low-rate regions (Idaho, Washington, Utah). After payback, solar electricity is essentially free for the remaining 15 to 20 years of panel warranty life. The cost to install solar guide breaks this down with regional payback calculations and buy vs lease comparison.
How these tools connect
A solar installation requires proper wire sizing from the inverter to the electrical panel. The wire size calculator handles this: input the inverter's output amperage and the distance to the panel, and it tells you the correct gauge with voltage drop check. For homes adding an EV charger alongside solar, the same calculator sizes the dedicated 240V circuit the charger requires (typically 6 AWG copper on a 50-amp breaker for a 40-amp Level 2 charger).