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How many solar panels do I need for my home?

Francisco CastroApril 29, 20192750

If you drive by a neighborhood with several solar-powered homes, you’ll notice that every system is different. Some have solar arrays that are bigger than others, taking up almost every inch of roof space. Others are much smaller, just a few solar modules.

So, if you’re in the market planning to join the solar energy revolution, the question arises, how many solar panels do I need? Solar panels are the most expensive part of any solar system, converting sunlight into electricity. They are made up of solar cells that regularly come in 60 or 72-cell modules and send that DC (direct current) electricity to an inverter, which transforms it into AC (alternating current) that comes out of the electricity sockets in your home.

The answer as to how many modules depends on a number of individual variables for your household, as well as your energy goals and future circumstances. If you have a bigger family or a lot more appliances than normal, you will definitely need more panels than your neighbor who has a smaller one. Similarly, how much of your energy needs do you want to offset with solar - 80%, 90% or 100%? 

Other things to consider are what direction your house is situated – north/south or east/west, which dictates whether you will have more or less sunshine available to you to convert into solar power. Another factor is how much shade your home receives. It’s important to know this because it affects solar panel energy output.

Energy needs

It all starts with your present energy needs. How much electricity do you consume in a month and how much of it you want to replace with solar power? If you look at your utility bill you should be able to calculate the total number of kilowatt hour (kWh) that you use for that period and add them up for an entire year. in 2016, the average annual electricity consumption for a U.S. residential utility customer was 10,766 kilowatt hours (kWh), according to the Energy Information Agency (EIA).

So, just for an example, let’s say you consume 10,000 kWh per year. That means that you consume an average of 833 kWh per month. Los Angeles receives 

If you live in Los Angeles, you receive about 5.62 sun peak hours per day. Those are the hours during which the intensity of sunlight is 1,000 watts per square meter. This amount changes throughout the seasons and is also affected by the time of day and the climate in the area where your house is located. 

So the formula to figure out your solar power system is 833 divided by 5.62 multiplied by 30 (833/168.6) = 4.9 kW

This means you would need a 5 kW solar power system to generate that amount of energy.

How many panels?

Armed with this information, you now have to determine how many solar panels would generate that much electricity.

Solar panels range from 45 watts and up. This represents the maximum amount of power that a specific panel produces. The lower the wattage of a panel, the more modules you will need to achieve 5 kWh. The higher the wattage, the fewer modules needed.

A 5kWh is the basically a 5,000 watt system. 

So let’s say you pick 300 watt solar panels. You would divide 5000 (5 kWh) by that 300 = 16.6 panels. 

Another way to estimate all this is by accessing the National Renewable Energy Laboratories (NREL), which gives you an approximately how many solar panels you need to produce a particular amount of power in a particular location.

For a more accurate statement not only on the number of panels you need for your home, but also the cost and even the packback period for that solar system, you can visit the Hahasmart price checker. All you need to do is put in your address and average cost of monthly electricity and they’ll recommend the correct solar power system for your needs. They also can recommend a design for that system.


Looking into the future

The calculations above only take into consideration your present needs, but that may change in the future. For instance, if you are planning to expand your family or add an item that consumes a high amount of energy, such as an air conditioner or perhaps an electric car, that is sure to change how much electricity you consume. 

If you’re hiring a contractor, make sure to discuss all these details with the company to determine your individual need, both current and future ones, so they can make the best determination. This is important because most solar panel systems are estimated to last about 25-30 years and it’s better to get right from the start, instead of trying to change it midway. 

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