Solar Panel Square Footage Calculators: Why Not to Use Them

Solar ROI
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Why You Shouldn't Use a Solar Panel Square Footage Calculator

A common misconception of solar panels is that the size of your home will determine how many you need. The idea is that a larger house with a bigger roof will use more energy than smaller houses. Therefore, it will need a larger solar installation to make up for that. This idea, however, is not correct. In this article, we’ll explain why it’s not correct and how you can get a more accurate estimate of how many panels you’ll need.

Why Square Footage Calculators Lead Users Astray

Square footage calculators are simple. They are tools found on the internet that claim to be able to calculate how many solar panels your home will need based only on roof size. They also sometimes implement location data, using the standard sun hours of your location to help make their estimate. Google provides a commonly used calculator.

What Problems Do Square Footage Calculators Have?

The above description is deceptively simple. The companies which put together these solar calculators bank on the idea that most potential solar homeowners won’t know how the process works. These calculators can then be used to sell larger solar installations that are strictly necessary.

The main reason why these calculators are unable to get a good estimate for the size of your solar installation is that there is not a big correlation between house size and energy use. Large homes with only one or two occupants is going to use less electricity than a small house with six occupants. The variation in electricity consumption is a problem which cannot be solved just be looking at roof size.

What About Other Types of Solar Calculators?

No online solar calculator will be able to give you a completely accurate appraisal of how much it would cost to go solar for your home. However, company specific calculators can give you a good starting point. These calculators will take into account the products the company stocks, the energy prices in your area, and other factors unique to your market. These calculators can be used to determine if it’s worth going for a free, in-person solar quote.

The Role Energy Use Plays in the Size of Your Solar Installation

While company specific solar calculators can be a useful tool, they’re only a rough starting point. Online calculators have trouble getting an exact number because the electricity usage of a given home is going to vary from another of a similar size.

The reason electricity usage varies is that the size of your home doesn’t really increase electricity usage beyond some minor heating and cooling increases. Rather, the electricity consumption of your home is determined by what appliances you have and how often you use them.

A home with only one resident, who does their laundry at a laundromat and rarely uses the air conditioner, is going to have a very low power use. On the other hand, a home with a family of seven, who run the washer and dryer all day, along with keeping the house very cool in the summer, is going to have a very high energy use. 

How To Estimate Your Home’s Energy Usage Through Your Appliances

Now that you understand why the size of your home isn’t necessarily the determining factor, we can move on to calculating your electricity use with your appliances. The amount of energy needed by an appliance, along with how often you use it, are the main places to look.

How To Use Your Appliances’ Wattage

A watt is a unit of energy. Your appliances will have a certain wattage, which is an estimate of the amount of electricity they use to start up and run. For example, a refrigerator may have a wattage of 305 W. This means that the refrigerator will take 305 W of electricity to start up and begin running. It will then consume 305 W of energy continuously while running.

Keep in Mind the Amount of Time You Use Appliances For

It is important to know the kind of appliances that you have. Some appliances will only use electricity during certain times. Your washing machine will only use the most electricity while you’re doing laundry. Some appliances, however, pull power throughout the day because we constantly use them. Your lights, air conditioning, refrigerator, and computers will all pull power throughout most of the day. 

It is for this reason that one of the key ways to reduce your electricity usage is through efficient appliances. Energy-efficient fridges and freezers are an excellent way to cut down the amount of money you owe on your power bill. This also holds true for purchasing energy-efficient bulbs as your lights go out.

When investigating your home’s electricity, keep track of how often you use your appliances over a few days. You’ll want to take note of how long you keep the lights on, how long your average laundry time is, and how long you keep your computer on each day, among other things.

Calculating Your Energy Usage Through Wattage and Time Used

Now that you’ve taken a look at each appliances’ wattage, followed by how often you use said appliances, it’s time to use those to calculate your home’s energy use. This can be done online. A common tool used is the Department of Energy’s Appliance Energy Calculator

Why Your Home’s Energy Use Matters for Calculating Solar Savings

Now that you’ve figured out your home’s energy use, it’s time to use that knowledge. The size of your solar installation is going to be based on this information. By knowing your home’s energy use ahead of time, you can avoid dishonest companies that try to sell you more stuff than you need.

What Is Solar Panel Wattage?

Solar panels are rated for certain wattages. For example, a solar panel may be rated for 300 W. This means that the panel will produce about that much electricity in one sun hour. Your whole installation’s wattage is, therefore, the combined wattages of each of the individual solar panels. If you have 30 solar modules, each with a wattage of 300 W, your system will have a total wattage of 9000 W (or 9 KW).

Variations in Solar Panel Electricity Production

The electricity production of individual solar panels will depend on a couple of factors. 

Firstly, having the right inverter will help maximize the amount of electricity they can create. A string inverter is sufficient for many homes. Others, however, may need hybrid string inverters or individual microinverters to get the best production. Having the right inverter for your situation will ensure that no power is wasted by system inefficiencies. 

Secondly, more efficient panels will produce more electricity. Polycrystalline panels, those made from multiple silicon crystals melted together, are generally less efficient. Monocrystalline panels, where silicon is poured and then sliced into bars, are generally more efficient. That means that a solar installation with 30 monocrystalline panels will produce more power than an installation with 30 polycrystalline panels. It is for this reason that Go Solar Group only offers monocrystalline solar panels, as we believe that polycrystalline panels are not worth your money.

Building the Right Installation for Your Home

Now that we understand how to calculate your home’s electricity use and also have a firm grasp on solar panel wattage ratings, it’s time to see how the two combine. Unsurprisingly, it’s a pretty simple combination. You need to find out how much energy your home uses in a day and install a system that matches, or exceeds, that.

Because you cannot install a solar panel system that exceeds your energy use without knowing your home’s electricity usage rates, you need to calculate that ahead of time. And, because this rate can only be determined by either measuring your appliance usage or contacting your energy company, simply looking at the size and location of your home will not work. 

As merely surveying the roof size and location of your home will not tell you how much solar you need, it’s far better to avoid square footage calculators. Take the time instead to learn more about your daily energy habits. With this knowledge, you can put together a solar installation that meets your energy needs and avoid dishonest solar companies.

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