How to calculate your home's solar energy needs?

How to calculate your  home's solar energy needs?

There are two main ways to approach this: a quick and easy method and a more detailed, accurate method.  

The Quick and Easy Method (Using Your Utility Bill)

This is the best place to start, as it gives you a solid overall number.

Step 1: Find Your Monthly kWh Usage
Look at your electricity bill (or a year's worth of bills for the best accuracy). Find the line that shows "kilowatt-hours (kWh) used" or something similar.

• For a rough estimate: Use your average monthly kWh. Let's say it's 900 kWh per month.

• For a better estimate: Add up your total kWh usage for the last 12 months and divide by 12. This accounts for seasonal changes (high AC in summer, heating in winter).

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Step 2: Calculate Your Daily kWh Usage
Simply divide your monthly average by 30.
900 kWh / 30 days = 30 kWh per day

Step 3: Estimate Your System Size (in kW)
Now, you need to figure out what size solar system will produce that much energy. This depends on your location (how much sun you get).

A common rule of thumb is that 1 kW of solar panels produces between 3-5 kWh of electricity per day. Sunnier states (AZ, CA) will be on the higher end; less sunny states (WA, MN) will be on the lower end.

• Formula: Daily kWh Needed ÷ Average Sun Hours per Day = System Size (kW)

• Let's assume you get 4.5 peak sun hours per day (a good national average):
  30 kWh / 4.5 hours = 6.66 kW system

So, you would need roughly a 6.7 kW solar system to cover 100% of your energy needs.

The Detailed and Accurate Method (Appliance Audit)

This method is more work but gives you a much deeper understanding of your energy consumption and helps you identify ways to save before going solar.

Step 1: List All Major Appliances and Their Wattage
Go around your house and make a list of everything that uses electricity. You can find the wattage on a label on the appliance itself or in its manual. Here's a common example:

Step 2: Calculate Daily kWh for Each Item
Use this formula: (Wattage × Hours Used) / 1000 = Daily kWh

• Example for AC: (3500 W × 4 hrs) / 1000 = 14 kWh

  
  

Step 3: Add It All Up
Sum the "Daily kWh" column. You'll notice this number (19 kWh in our example) might be lower than the one from your utility bill (30 kWh). That's because this list inevitably misses things (garage door opener, well pump, phone chargers, etc.). The bill method is more comprehensive.

Step 4: Factor in Efficiency and Future Changes

• System Losses: Solar systems aren't 100% efficient due to inverter losses, dirt on panels, and wiring. Multiply your total daily kWh by 1.2 to add a 20% buffer.
  30 kWh × 1.2 = 36 kWh daily needed

• Future Plans: Are you buying an electric vehicle? Switching from gas to an electric heat pump? Adding a pool? Factor in this future electricity use now so you don't undersize your system.

Step 5: Use the Same System Size Formula
(Adjusted Daily kWh) ÷ (Peak Sun Hours) = System Size (kW)
36 kWh / 4.5 hrs = 8 kW system

Next Steps and Professional Help

1. Use Online Calculators: Tools like the National Renewable Energy Laboratory's (NREL) PVWatts Calculator are fantastic. You input your address and average monthly bill, and it calculates system size, production, and even estimated costs and savings based on incredibly detailed local weather data.

2. Get Quotes from Installers: This is the most important step. we will provide a detailed energy analysis and quote for free.

• We will pull your exact utility data.

• We use satellite imagery to model your roof's sun exposure, shading from trees, and the perfect angle for panels.

• We proposal will show the exact system size, estimated production, and financial payback period.

Key Considerations Before You Decide:

• Net Metering: Check if your utility offers net metering. This allows you to sell excess power you generate back to the grid, effectively using the grid as a "battery." This greatly impacts the economics of your system.

• Your Roof: Is it old? Does it have enough unshaded space? South-facing roofs are ideal in the northern hemisphere.

• Batteries: Do you want backup power for outages? Adding a battery (like a Tesla Powerwall) will increase the cost significantly but provides energy security. You might also size your system slightly larger to charge the battery.

Summary

• Fastest Method: Check your electricity bill for monthly kWh usage, divide by 30 to get daily use, then divide by your local peak sun hours (4-5) to get system size in kW.

• Best Method: Get free quotes from 2-3 certified local installers. They have the tools and expertise to give you the most accurate number and answer all your questions.

By starting with your own calculations, you'll be an informed consumer when talking to installers and can better evaluate their proposals. Good luck!