Calculator Solar Panel

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Solar Panel System Estimator

300W (Standard) 350W (High Efficiency) 400W (Premium) 450W (Ultra)

System Recommendations:

Estimated Panels Needed
0
System Size (kW)
0.0
Annual Production (kWh)
0
Estimated Annual Savings
$0

*Calculations assume 78% system efficiency considering inverter losses, wiring, and dirt.

function calculateSolar() { var monthlyKwh = parseFloat(document.getElementById('monthlyKwh').value); var sunHours = parseFloat(document.getElementById('sunHours').value); var panelWatts = parseFloat(document.getElementById('panelWatts').value); var monthlyBill = parseFloat(document.getElementById('monthlyBill').value); var efficiencyFactor = 0.78; if (!monthlyKwh || !sunHours || !panelWatts) { alert("Please enter all required energy consumption and sunlight data."); return; } // 1. Calculate Daily Energy Requirement var dailyKwhNeeded = monthlyKwh / 30.42; // 2. Calculate Required DC System Size (kW) // Formula: (Daily kWh) / (Sun Hours * Efficiency) var systemSizeKw = dailyKwhNeeded / (sunHours * efficiencyFactor); // 3. Calculate Number of Panels var numPanels = Math.ceil((systemSizeKw * 1000) / panelWatts); // 4. Recalculate Actual System Size based on rounded panel count var actualSystemSize = (numPanels * panelWatts) / 1000; // 5. Calculate Annual Production var annualProduction = actualSystemSize * sunHours * efficiencyFactor * 365; // 6. Savings (Simplified: Assumes 100% offset) var yearlySavings = monthlyBill * 12; // Display Results document.getElementById('solar-results').style.display = 'block'; document.getElementById('panelsNeeded').innerHTML = numPanels + " Panels"; document.getElementById('systemSize').innerHTML = actualSystemSize.toFixed(2) + " kW"; document.getElementById('annualKwh').innerHTML = Math.round(annualProduction).toLocaleString() + " kWh"; document.getElementById('annualSavings').innerHTML = "$" + Math.round(yearlySavings).toLocaleString(); }

How to Calculate Your Solar Panel Requirements

Switching to solar energy is one of the most effective ways to reduce your carbon footprint and eliminate monthly utility bills. However, determining the exact number of panels your roof requires involves understanding your specific energy consumption patterns and regional solar potential.

Key Factors in Solar Calculation

To get an accurate estimate from our solar panel calculator, you need to consider three primary variables:

  • Average Monthly Consumption: Found on your utility bill, this is the total Kilowatt-hours (kWh) you use. It fluctuates seasonally, so using a 12-month average is best.
  • Peak Sun Hours: This is not the total daylight hours, but the intensity of sunlight. Areas like Arizona might have 6 peak hours, while northern states may average 3.5 to 4.
  • Panel Efficiency: Modern solar panels typically range from 300W to 450W. Higher wattage means you need fewer physical panels to achieve the same energy output.

The Solar Math: A Practical Example

Let's look at a typical scenario for a household in a sunny region:

Suppose you use 1,000 kWh per month and live in an area with 5 peak sun hours per day. Using the standard system efficiency of 78% (accounting for AC/DC conversion losses and environmental factors):

  1. Daily energy need: 1,000 kWh / 30 days = 33.33 kWh per day.
  2. System size needed: 33.33 / (5 sun hours * 0.78 efficiency) = 8.55 kW system.
  3. Number of 400W panels: 8,550 Watts / 400 Watts = 22 panels.

Why System Efficiency Matters

It is a common mistake to assume a 10kW system produces 10kW of usable electricity every hour the sun is out. Real-world conditions include "derate factors" such as:

  • Inverter Efficiency: Converting DC power from panels to AC power for your home loses about 3-5% energy.
  • Soiling: Dust, pollen, and bird droppings can reduce output by 2% to 5%.
  • Temperature: Solar panels actually lose efficiency as they get extremely hot.
  • Wiring Losses: Small amounts of resistance in the cables lead to minor power drops.

Financial Impact of Going Solar

The average American household pays roughly $1,500 to $2,000 annually in electricity costs. By installing a system sized to 100% of your needs, you can effectively "lock in" your energy rate for the next 25 years. Most homeowners see a "break-even" point (Payback Period) between 6 to 10 years, after which the electricity produced is essentially free.

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