Solar System Sizing Guide — SolarPanelKits

Step 1

Calculate Your Daily Energy Load

List every appliance you plan to run, its wattage, and how many hours per day it operates. Multiply watts × hours to get watt-hours (Wh). Add them all up.

Appliance	Watts	Hours/Day	Wh/Day
LED Lights (10)	100	5	500
Refrigerator	120	24	2,880
Water Pump	800	1	800
Laptop	60	4	240
Phone Charger (2)	20	2	40
Fans (2)	80	6	480
Total Daily Load			4,940 Wh

Step 2

Size Your Panel Array

Divide your daily load by your location's peak sun hours (PSH). Then add 25% for system losses. Most of the continental US gets 4–6 PSH.

Panel Watts = (Daily Load ÷ Peak Sun Hours) × 1.25
Example: (4,940 Wh ÷ 5 PSH) × 1.25 = 1,235W of panels
→ 4 × 400W panels or 6 × 200W panels

Step 3

Size Your Battery Bank

For LiFePO4 batteries, you can safely discharge to 20% (80% usable). Plan for 1–3 days of autonomy depending on weather and risk tolerance.

Battery Ah = (Daily Load × Days of Autonomy) ÷ (System Voltage × DoD)
Example (2-day, 48V): (4,940 × 2) ÷ (48 × 0.8) = 257 Ah at 48V
→ 3 × 48V 100Ah batteries

Step 4

Size Your Charge Controller

Divide your total panel wattage by your battery voltage to get the minimum controller amperage. Always go one size up.

Controller Amps = Panel Watts ÷ Battery Voltage
Example: 1,600W ÷ 48V = 33.3A → use a 40A MPPT controller

Step 5

Size Your Inverter

Your inverter must handle your peak simultaneous load (not daily total). Add up everything that might run at once, then add 20% for surge.

Inverter Watts = Peak Simultaneous Load × 1.2
Example: 1,080W × 1.2 = 1,296W → use a 1,500W or 2,000W pure sine wave inverter

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