How to Estimate Solar Photovoltaic System for Our Home?

Solar photovoltaic is one of the most attractive renewable sources today.  It is not only for the benefit of our environment, the cost is also reduced multiple times than before. If we compare the price of solar photovoltaic in 2009, today’s price is 70% cheaper.

Although we have estimated that the average price for solar photovoltaic components in the previous article as USD4.00 per watt, that is the price for a single home installation. If we form a community and create a larger project, we can have even bigger savings. Solar photovoltaic panels are much cheaper when you purchase in bulk than you do personal purchase. In fact if we could grab the government incentives, we could have much cheaper price per kWh than the electricity from coal.

We just recently launch the ecogreen4us Community as one part of this website. One of the main purposes is for all readers to form local communities or local projects. It is a free service and for instance you could form a community for local solar project.

Share the idea and gain more knowledge from other members. Some members might already have an experience and they can help you on the topic. In this way, hopefully any green project could be developed without big mistakes. Let’s us check how to estimate the solar photovoltaic system for our home.

Step 1 – Monthly Usage of Your Electricity Bill

You have to check your monthly usage of electricity from your previous bills. There are few methods how to calculate this. The first and the most recommended method is to take the average in kWh of your monthly electricity bill.

For instance, if you keep your bill for one year or 12 months. You could simply sum all bills and then divided it by 12. Then you can get the average amount of power usage for 1 month. Please do not take the average of how much you pay for the bill rather than the average of electric power in kWh that you use.

This is a sample of an electric bill for one user. The user consumes electricity of 765 kWh for that particular month. If you have more bills for longer period, you also could use them because summing up for much longer period makes the accuracy even better.

Another method is to find the best month that your area has the highest solar potential energy. You simply pick that month and refer it with your previous electricity bill. That will be your reference for solar energy systems installation.

The highest solar energy potential from January till December could be referred from the NREL website. This information is for the United States. For other countries we could not find any available free sources from internet. Readers could check with local government websites or offices to find those numbers.

On the NREL page you could check maps under titles PV Solar Radiation (10 km)—Static Maps and PV Solar Radiation (40km)—Static Maps as reference.

Nevertheless, most people agreed that using the monthly average of electricity bill as the easiest method. It is very difficult to estimate by picking up the best month with the best solar sun hours. After you have the number then write it down. Now you have already the average monthly usage of electricity for your home.

Step 2 – Sun Hours or Solar Photovoltaic (PV) Resource

Sun hours or solar photovoltaic (PV) resource is the average solar resources which is measured in kWh/m2 per day. It means that the average power received from solar or sun for 1 meter squared area within one day. They measured these numbers for couple of years, sum up and then average it entirely to be within one day.

Please do not confuse with so many units and numbers. Another common or regular term for sun hours is insolation. Insolation is regularly calculated in MJ/m2, megajoules per square meter or J/cm2, joules per square centimeter.

This unit is recommended by World Meteorological Organization. Joule is unit of energy and insolation is a measure of solar radiation on a surface area and recorded during a given time.

Power (Watt) = Energy (Joule)/time

pv usaFrom this map you could estimate sun hours for your home. This map is produced by NREL and could be obtained from the same page that we mentioned earlier. Once you get approximately the value of sun hours in kWh/m2 per day then write it down.

We tried to find similar measurements for other countries which are freely available on internet. The nearest information that we could find is from solargis.info. Readers could check their website to find the information for sun hours. Try to adjust the measurements to be in unit of kWh/m2 per day.

Calculation of Solar Photovoltaic System

This is an example after you have everything what you need to calculate the right solar energy systems (photovoltaic) for your home from step 1 and step 2 above. This calculation is a practical calculation and please don’t think of units as regular calculation in physics. In this way it is easier to estimate for solar energy systems for your home.

From step 1 your monthly electricity usage is = 765 kWh

Thus your daily usage is approximately = 765/30 = 25.5 kWh (divided by 30 days in a month)

Approximately 25% inefficiency shall occur in the solar energy system such as DC to AC conversion, battery etc. For that reason we need to add 25% more to tolerate with the inefficiencies.

Thus the number would be 25.5 X 125% = 31.88 kWh

Note: 125% after adding more 25% becoming 125%

For instance from the step 2, you obtained the sun hours measurement for your area is 6 kWh/m2 per day.

Thus if you would like to cover 100% of your home with solar energy system, you need solar energy system producing: 100% X 31.88/6 = 5.31 DC kW

If you would like only 50% of the electricity usage to be with solar energy then, you need solar energy system producing: 50% X 31.88/6 = 2.66 DC kW

1 DC kWh eliminates approximately 18,600 lbs. of carbon dioxide or CO2 per year. Planting a tree approximately eliminates 690 lbs. of carbon dioxide or CO2 per year.  Hence if we use solar photovoltaic to generate electricity with 2.66 DC kW, we eliminate approximately 49,476 lbs. of CO2 per year and equivalent to planting 72 trees. Thanks for reading.

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3 thoughts on “How to Estimate Solar Photovoltaic System for Our Home?

  1. I do believe solar photovoltaic power is a great easy and affordable solution to power. In the first video the woman really emphasized that her new lifestyle was not only Eco friendly but also extremely fun. She said its not hard to focus on the positive. I think this form of electricity is not commonly used in everyday homes because people are scared. They are scared to give up their IPads and televisions. But in reality all this article is trying to do is encourage people to lower their carbon footprint. Not get rid of it completely. It is difficult to deduce ones Eco footprint due to the media today and how it is implied one must have all the newest technological advances in order to be happy. Yet in reality these advances are diminishing our access to true happiness. The woman in the video was extremely happy and pleased with her life. So why are we afraid of happiness. Lowering ones Eco footprint ultimately can increase ones happiness

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