# Solar Power for Homes, what a homeowner must know?

Updated on October 13, 2011

## What is Solar Power?

The sun radiate enormous amount of radiation. Devices called solar electric panels use the photovoltaic effect to convert sun radiation (photons) into electric power (electrons). When the Sun is perpendicular to the solar panel, the irradiation intensity is 93 Watts over one square foot. The solar panel conversion efficiency is not 100%, due to inherent constraints of the semiconductor material from which the panel is built. The actual efficiency for panels that are available on the market is more like 12% to 18%, therefore our one square foot solar panel will produce 11.2 Watt (for a 12% efficient panel) to 16.8 Watt (for a 18% efficient panel). A typical US home will need production capability of 3,000 Watts, and to get that it needs 178 square feet of solar panels. (3,000 divided by 16.8). These panels will produce 540 KW-h every month (3 kW multiply by effective 6 hours every day multiply by 30 days in a month)

Most homeowners heard about solar power, many consider buying and installing a solar power for homes system, and many struggle with the following questions:

1. What is the right size for my system?
2. How can I finance the system?
3. Can I install the system on my premises?
4. Does a solar power system make sense for me?

## What is the right size of the solar power system?

If your home is connected to the grid, look into your electric bills, see what is your average monthly consumption in KW-h and decide what proportion of that consumption you want your system to generate. For example, if your home consume 900 KW-h (typical to many US homes), and you want to produce half of it, you need to produce 450KW-h every month. This is 15 KW-h every day (450 divided by 30), and you will need solar panels that produce 2500 Watts (15,000 divided by 6).

If your home is off-grid (not connected to the grid), you need to supply your entire electricity consumption by your own generators. You will need to store electrical power during day time on a bank of deep cycle batteries that can be used overnight and you will also need a back-up generator such as a diesel generator.

## How to finance?

A solar power system is relatively expensive. You may assume \$4-6 per watt including the DC to AC inverter, wiring, control, installation, control and permits. The US government will credit you, until tax year 2016 with 30% of the expense with no limit.

Still you wonder how to finance the balance, in most cases well above \$10,000. The main financing avenues are:

1. Taking a long term solar energy loan (very much like a mortgage)
2. Leasing the equipment through leasing company
3. Let a 3rd party company install and own the solar system on your premises and buy the electricity from this company. One active company in this business is Sunrun, another is Solar City.

## Can I install the solar system?

Best is to install the panels on a tilted roof facing South or "almost South" (such as South-East). You will need for a 3,000 Watts solar system, with 15% efficiency, more than 215 square feet available on your roof.

## Does solar power make sense to you?

If you are a green energy supporter, a solar power is an obvious choice.

If you look into return on investment, the situation becomes more attractive if:

1. The price per KW-h is relatively high in your region
2. The long term interest rate is relatively low
3. If the state you live in is generous in tax credits and incentives (California for example)

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• Jack Lee

3 years ago from Yorktown NY

Interesting. Any idea what will happen to solar power homes when the tax credits expire at end of 2016?

• Farmer Brown

7 years ago

Great layout for solar energy. There's so much to learn, especially as more and more US residents are looking at putting solar panels on their own homes. The technology is catching up with the interest.

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