What Size PV System do I Need?

Matching Your Load With Your PV System

If you have determined that PV is the best way to meet your energy needs, you need to size your system to effectively meet your daily load. You will need the answers to the following questions and the assistance of an expert to make an informed decision.

What is your budget? Remember, in New Jersey and many other states, the government offers rebates and tax credits at the federal and state levels. It is cheaper overall to install a larger system all at once than to only add a few kilowatt system and add later. A 10 kw system is generally required to qualify for net metering, and for registration online to earn SRECs.

Does your load need to be met all day every day? If not, what percentage of your energy needs do you hope to supply with your system?

Will you need to stay hooked into the grid if there are extended periods when the sun does not shine? New Jersey and surrounding states can experience periods of cloudiness for days, especially in winter.

What are has your average electricity usage been over the past few years?

Does your utility company allow net metering (will they let you have energy when you need it, and buy back from you when you have excess)?

Once you have determined what your budget and expected usage are, you can calculate the size system you should purchase. A chart is available for calculating square footage of roofing needed by the efficiency of your proposed PV modules here.

Your first step is to determine your average daily usage in kilowatt hours. Most bills will have this displayed either as a daily average over the month or the total kilowatt hours used over the month. Look at your average over the year to get the best estimate of your usage.

Use the chart found here to estimate the number of clear, partially cloudy and cloudy days per year in your state or town. This will give you an idea of how much monthly production you can have at different times of year.

Arosa Solar can help you estimate the size PV system you will need to produce any percentage of your building’s energy. You can work the figures backwards if you are buying based on a budget, multiplying the number of sunlight hours / day times the number of kilowatts a prospective system would produce. This will give you an idea of what percentage of your home’s power could be replaced with solar energy on an average day.

Go solar!

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1 Response so far »

  1. 1

    Bmac said,

    Love it, the German Federal Association of the Solar Industry reported that there were 1,300,000 solar plants in Germany in 2006. 220,000 new plants were erected in 2006 alone. In Germany, solar thermal plants are predominantly used to generate hot water and to augment the heating system in private households, but they are also increasingly being used in larger community facilities and open air swimming pools. Solar is going to be a big pull. Whether we see that now or later …


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