How Many Solar Panels Do I Need To Power A House?

Luckily, solar energy got cheaper than it ever was, because of falling cost and the rising popularity of Photovoltaic solar panels. Solar panels are now used more than ever, all around the globe. These are also used in houses for private uses.

But before buying solar panels, first, you need to know the number of groups you need to have, to power your house. There are some simple steps that you have to follow to calculate the amount of power you need to produce for a regular home.

Based on this calculation, you are going to buy the required number of solar panels. Last month, one of my neighbors asked me to help him out with this problem.

Unfortunately, I did not know much about it and hence, both of us talked to some professional installers and got to know about the procedures following which we can calculate the number of solar panels needed for a particular house. Here, I am going to write in details about the whole thing.

Calculation Of A Number Of Panels

While planning to set a solar system, it is essential to know the name of the groups you need to fulfill in order to satisfy your power requirement.

The number of panels that are required mostly depends on how costly it will be to do the whole installation. A systematic approach towards how to calculate this is mentioned below:

Average Electricity Use

Calculate the average electricity usage each day in watts by from your electricity bill of a single month. Add the whole kilowatt hours you used through-out the year and divide it by 365 to get the average electricity use. Then, multiply the result by a thousand to get the result in watts.

If your electric company provided this calculation on the bill, then you need not do all these.

Average Sunlight Hours

Figure out the average sunlight hours per day in the area you live in. For doing this, you can use an online solar calculator. To do that, you only need to know about your location.

Number Of Watts

Find out the number of watts of power that you use per day and divide it by the average hours of sunlight each day. The result that you get is the number of watts that you need to produce every hour.


Get the watts that you need to produce each hour and divide it by the rating of panels which you are willing to buy and then, round it up..

As there are differences in watt ratings in different groups, you have to choose exactly which one you are supposed to purchase. 

Factors That Affect Panel Efficiency

Differences in solar panels mostly depend on their output efficiency. All solar panels are not alike.

Ones which are Photovoltaic and which are commonly used in residences have wattages ranging from 150 watts to 370 watts each group, based on the size of the group and its efficiency to convert sunlight into energy and also on the technology of the cell.

As for example, solar cells which do not have grid lines on their front side tend to absorb sunlight more than generic cells, but they do not have issues like corrosion or cracking.

A micro-inverter is placed on each panel which can optimize the conversion of power at the source, other than one big inverter placed just on one side of the house. Because of this, it gets a bit troublesome for you to determine which solar panels are appropriate for you and how many you are going to need for your house.

Point to be noted is, if the panels are more efficient then they will produce a lot of wattages. Hence you will need less number of them on your roof to get the required amount of power.

Usually, solar panels generate around 250 watts per panel, though the efficiency varies. Along with that, SunPower panels are said to be the most efficient solar panels on the market.

Effects Of Solar Panel Size

You have to bother about the size and numbers of solar panels that you are going to install on your roof if it is small and has an unusual shape. On the other hand, if you have a big tent, you can go for larger solar panels which are low in cost, to get the amount of power you need to produce.

But if the area of the roof where you are willing to install your panels is not that spacious, it will be better to buy several small groups with high efficiency to get the desired output.

Recently, the dimensions of a typical solar panel are around 65 inches by 39 inches having some variation based on the manufacturer. Panels manufactured by SunPower are 61.3 inches by 41.2 inches.

The dimensions of the groups have been like these for an extended period without any alteration, though the output and efficiency went through drastic changes for overall betterment. 

If you keep the points mentioned above into consideration, it will not be a hard task for you to choose the right size and number of panels for your house. In inclusion, you can get a professional installer who will assess the architecture of your roof and things that need to be considered.


Along with all the above calculations, you have to consider how long you get to have sunlight throughout each day as that has an impact on the energy that will be gained and stored by your solar panels. Doing all the math may seem like a lot of work, but it will save you a lot of time and hassle afterward.

If you do not have a clear idea about your house’s energy requirement and you wind up purchasing panels which are not sufficient for generating the required amount of power, you may have to alter the whole system which will cost you even more money and make you go through a lot of hassle.

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