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How Many Solar Panels Do I Need?
Apr12

How Many Solar Panels Do I Need?

How to calculate a quick, easy GUESStimate for sizing a PV system. “How much will it cost to power my XX,XXX square foot house?” “How many solar panels do I need to eliminate my electric bill?” We get questions like this every day from homeowners in the beginning stages of going solar. For all intents and purposes, it’s pretty much impossible to give you a number based on the size of your house or the dollar amount of your electric bill – it’s all going to depend on the load.  Though I hesitate to give a rough number like this, sometimes you do need a ballpark figure to start things off. Alright, here we go: To begin, calculate your average energy usage in kWh.  Collect your electric bills for the past 12 months or more. Get an average of kWh used on a monthly basis.  Let’s say that this number is 1100 kWh per month. Now divide your average monthly usage by 30 to get your average daily kWh usage.  In this case, it would be about 37kWh per day. To keep things simple for this rough estimate, we’ll assume that a 250W solar panel will produce about 1kWh a day.  **Keep in mind that this is a rough estimate, based on a site location getting 4 hours of sunlight per day** Assuming that you use about 37 kWh per day, you would need about 37 solar panels to meet 100% of your average energy needs. Based on your current usage, how much of this do you want to offset with a solar power system? 100% …75%…. 50% ?    Multiply accordingly. Let’s say you wanted your solar system to account for 80% of your energy consumption. 37 kWh per day x 0.80  = 29.6 kWh Since one solar panel produces about 1 kWh per day, you would use 30 solar panels to account for 80% of your average consumption. The purpose of this is to give a rough idea of how many solar panels you will need.  This sizing tool provides a quick number to go off of as you’re shopping around- it’s not a replacement for having an electrical contractor design a system for you. Once you’ve calculated your average kWh use and determined the percentage that you plan to offset with solar, get a free solar quote from GoGreenSolar.com 😉  We’ll help you design a complete system that’s specific to your roof and geographical location. Any questions?...

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PVWatts makes estimating solar power easy

PVWatts is a performance calculator for grid connected solar power systems developed by NREL (National Renewable Energy Lab) to help non-solar expert conduct estimates for grid-connected solar photovoltaic systems within the USA. The calculator uses hourly Typical Meteorological Year weather data to forecast how many kilowatt hours (kWh) you will generate on a monthly or annual basis. You can enter parameters such as fixed mounted solar panels, solar panels on a tracker and even the azimuth to properly forecast different solar power system setups. Both version 1 and 2 of the calculator are provided for free on the PVWatts Website. I ran a estimate of how a 4.0 kilowatt (kW) solar power system would perform in Los Angeles using version 1 of the PVWatts calculator. Check out my assumptions and system performance: Station Identification City: Los_Angeles State: CA Latitude: 33.93° N Longitude: 118.40° W Elevation: 32 m PV System Specifications DC Rating: 4.0 kW DC to AC Derate Factor: 0.770 AC Rating: 3.1 kW Array Type: Fixed Tilt Array Tilt: 33.9° Array Azimuth: 180.0° Energy Specifications Cost of Electricity: 12.5 ¢/kWh Results Month Solar Radiation(kWh/m2/day) AC Energy(kWh) Energy Value($) 1 4.44 401 50.12 2 5.35 441 55.12 3 5.62 506 63.25 4 6.05 522 65.25 5 6.19 548 68.50 6 6.17 526 65.75 7 6.48 567 70.88 8 6.68 582 72.75 9 5.78 487 60.88 10 5.43 480 60.00 11 4.84 420 52.50 12 4.46 398 49.75 Year 5.63 5879 734.88 Whats the performance of a 4.0kW system in your neck of the woods? go ahead feel free to post and discuss your results...

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Estimating the size of a solar power system using the square footage of your home or business

Many consumers always tell me the square footage of their home or business and expect a quote for a solar power system based off the square footage. You can use a general rule of thumb to estimate the size of a system of 2 watts of solar power per square feet. So lets say you had a 2000 square feet home and you were looking to size up a solar power system to eliminate your bill. 2 watts * 2000 square feet = 4000 = 4 kilowatt So in the case above for the homeowner above, they would need 4kW system to meet their entire electrical needs. This is obviously a very rough estimate of how much solar power you would need to eliminate your electric bill, although I suppose it is a great place to start your analysis. If you are looking for a more accurate estimate start by gathering 12 months of electric bills and look at your monthly kWh (kilowatt hours) usage. This will give you an idea of how much electricity you are using which can give you an accurate picture of how much solar power you would need to reduce your...

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