How Many Solar Panels Do I Need?

How Many Solar Panels Do I Need?

Anthony Barnes

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So, you want to trick your pool or home out with solar panels.

If you are off-grid, trying to homestead, or generally trying to rely less on the power grid, they can be a great choice!

However, it can be easy to over or underestimate the amount of power your home will need, and therefore how many solar panels you should have installed, especially as every person’s preferred energy usage varies so dramatically!

General Guidelines

With all that being said, there is no one size fits all answer for what is best for you, but here are some general guidelines:

The average household uses about 1kW per month (that’s 1000 Watts) in electricity.

This means that if you live in an area where the sun shines most of the year, you could install enough panels to generate up to 6kWh of electricity per month.

That would cover around half of your monthly needs.

The average American home has 3 bedrooms, 2 bathrooms, and a total living space of approximately 1500 square feet.

For this example, we will assume that each room is equal in terms of lighting, heating, cooling, and appliances.

If you have more than two rooms, you may need to add additional panels.

If you plan to use your panels primarily for lighting, then you may not need as much capacity as someone who plans to run their entire house with them.

If you are planning to heat water, then you will likely need more capacity than someone who only wants to charge their electronics.

How Much Energy Do You Use?

This is the very first step in determining how many solar panels you will need. 

The best way to see what you currently use is by looking directly at your recent utility and energy bills.

Having something like a smart meter is a great way of getting an accurate picture of what you and your family use monthly so that you can figure out your average watt usage, thus determining how many solar panels you need.

Calculate your average electricity usage. Look for “kilowatt-hours used” or something similar and then note the length represented (this will usually be 30 days)

If your electricity bill doesn’t show kilowatt-hours consumed, check the beginning and ending meter readings.

Subtract the previous reading from the current one.

If your bill doesn’t show a daily average, simply divide the monthly or yearly average by 30 or 365, respectively, and then multiply by 24 to determine your daily average electricity usage.

You’ll need to know how much power you’re using at any given time, so multiply that number by the total time the electricity was being used.

Your average daily energy consumption is the target daily average for calculating your solar needs.

That’s how many kilowatt-hours of energy your solar system needs to produce if you want it to cover most if not every one of your electricity needs.

It’s critical to understand that solar panels don‘t operate at their highest levels 24/7.

For example, weather conditions, such as rain, can temporarily reduce your systems’ efficiency.

Experts suggest adding a 25% cushion to your target daily average so that you can generate all the energy you need and never be caught short!

Cost Of Solar Panels

If you are looking at installing solar panels, make sure that you know exactly what you need before you start shopping.

You don’t want to get stuck paying for something you don’t need.

While the costs of installation vary from state to state, they typically range between $5-$20/watt.

The cost can go higher depending on the type of panel you choose, whether you hire a professional installer, etc.

Not All Solar Panels Are Created Equal

There are several different types of solar panels available today.

Each type comes with its pros and cons, so it is important to understand what you are getting into before making any decisions.

Here are the main types of solar panels available:

1. Monocrystalline Solar Panels

These are the most efficient solar panels currently available. They are also very expensive.

While these panels do last longer than other types, they are still a relatively new technology and may require replacement after 20 years.

2. Polycrystalline Solar Panels 

These are slightly cheaper than monocrystalline panels, but they are made from older technology.

They tend to last longer, but they are not nearly as efficient as monocrystalline panels.

3. Thin Film Solar Panels 

These are newer technologies that are even less efficient than polycrystalline panels.

Because they are thin films, they can be applied directly onto glass windows without having to drill holes through the window first.

They are also much easier to apply than traditional solar panels.

4. Hybrid Solar Panels 

These are a combination of both monocrystalline and polycrystalline cells.

They are more affordable than monocrystalline cells, but they are not quite as efficient.

5. CdTe Solar Cells 

These are less common than the others, but they are an excellent choice for those who want to reduce their carbon footprint.

They are extremely efficient, but their materials are also potentially toxic, which means you probably don’t want them around your pool, ay?

6. Amorphous Silicon Solar Panels 

These are the least expensive option out there. Unfortunately, they are also among the least efficient options.

What’s more, it takes a lot of energy to create amorphous silicon, which makes it one of the least desirable options.

What Affects Solar Panel Efficiency?

The efficiency of solar panels depends on many factors, including the following:

  • What kind of material the solar cell is made of – monocrystalline or polycrystalline. This affects how long the panel lasts.
  • How thick the solar cell is. A thicker cell means fewer photons hit each square inch, lowering efficiency.
  • Whether the solar cell has been exposed to sunlight or not – if it hasn’t been exposed to sunlight in a while, it will lose some of its efficiency.
  • Where the solar cell is installed on a roof or ground mount. Roof mounts are generally more efficient than ground mounts because they allow for better airflow and light exposure.
  • If the solar cell has been damaged by hail or other weather conditions. Damaged solar cells have lower efficiencies than undamaged ones.

Solar Power Systems – The Basics

Solar Power Systems - The Basics

A solar power system consists of three basic parts: the solar module(s), the battery bank, and the inverter.

Solar Modules

Solar modules come in two varieties: crystalline and thin film.

Crystalline solar modules use single crystals of silicon as the base material, whereas thin-film solar modules use flat sheets of materials such as cadmium telluride (CdTe) or copper indium gallium selenide (CIGS).

Most residential installations use crystalline solar modules, although thin-film solar modules can be highly practical and affordable.

Crystalline Solar Panels

There are two types of crystalline solar panels: mono and poly.

Monocrystalline panels consist of only one type of crystal, usually silicon.

Polycrystalline panels contain several different kinds of crystals, usually silicon, germanium, and/or cesium.

Both mono and polycrystalline panels produce electricity when exposed to sunlight.

Thin Film Solar Panels 

Thin-film solar panels are made from layers of various metals and semiconductors that are bonded together with a transparent conductive oxide (TCO).

TCOs are typically made from tin dioxide (SnO2) or zinc oxide (ZnO).

These materials are inexpensive, making thin-film solar panels an economical option.

Solar Batteries

Batteries store electrical current produced by solar modules.

There are two main types of batteries used in solar systems: lead-acid and lithium-ion.

Lead-acid batteries are cheap, but they can be dangerous due to the risk of fire.

Lithium-ion batteries are safer, but they cost significantly more than lead-acid batteries.

Inverters

An inverter converts direct current (DC) into alternating current (AC).

In most cases, this conversion happens automatically, but you may need to install an inverter if your solar system produces too much DC.

Installing A Solar System

The first step in installing a solar system is finding out what size system you want.

You’ll also need to decide where you want to place the system.

The next steps depend on whether you plan to buy or lease a solar system.

For buying a system, you’ll need to find a contractor who specializes in solar installation.

Contractors often work through local home improvement stores and contractors associations.

Leasing a system requires less upfront investment, so it’s easier to do yourself.

However, you will need to hire someone to help you install the system.

If you choose to go it alone, here are some things to consider before starting your project:

  • Determine how many watts of energy you expect to generate each month. This number depends on your location, time of year, and amount of sunshine.
  • Decide which type of solar panel you want—mono or polycrystalline.
  • Find out what kind of battery you should use.
  • Consider how long you want the system to last.
  • Choose a mounting method for the solar module.
  • Determine how you want to connect the solar module to the grid.

Solar Installation Services

Solar Installation Services

You can hire a professional installer to help you install a solar system.

If you have experience working with power tools, you might be able to complete the job yourself.

Otherwise, hiring a pro is likely to save money in the long term and provide better results.

Before Hiring a Professional Installer

  • Check references from other homeowners. Ask them about their experiences with the company and its employees.
  • Look at reviews online. Review sites like Yelp and Angie’s List offer ratings and comments from real customers.
  • Contact the Better Business Bureau. The BBB offers information about complaints against companies and helps consumers resolve problems.
  • Call the state licensing board for your area. Some states require contractors to be licensed. Others don’t. Be sure to check with your state’s agency to make sure you aren’t violating any laws.

Types Of Systems

There are three basic types of solar systems: photovoltaic (PV), concentrated PV, and thermal. Each has advantages and disadvantages.

Photovoltaic (Pv) Systems

A photovoltaic system uses solar cells to convert sunlight directly into electricity.

Photovoltaic systems produce DC electricity that must be converted into AC electricity by an inverter.

Advantages

  • They’re easy to set up and maintain.
  • They don’t emit harmful gases.
  • They can be used indoors.

Disadvantages

  • They are expensive. They take several years to pay off.

Concentrated PV Systems

Concentrated PV systems use mirrors to concentrate light onto solar panels.

Concentrated PV systems can reduce the cost of the solar modules needed because they allow more light to hit the same surface area.

Advantages

  • They’re cheaper than conventional PV systems.
  • They can operate in cloudy weather.

Disadvantages

  • They’ve been criticized for creating glare.

Thermal Systems

Thermal systems use heat from the sun to warm water.

Thermal systems can be used both outdoors and indoors. They also don’t create pollution.

Advantages

  • They‘re inexpensive.
  • They don’t need batteries.

Disadvantages

  • They’re inefficient.
  • They can only be used during daylight hours.

How Much Sunlight Do You Get In Your Area?

This is going to be a big deciding factor when it comes to how many panels you want to buy.

The amount of time when the sun is at its highest altitude directly impacts the amount of energy your home solar system can generate.

For example, if your city has an average of 100 peak sunlight hours per year, you can expect to have more energy usage out of your solar panels than if your city had an average of 50 peak sunlight hours per year. 

It doesn’t mean a Seattle homeowner can’t go solar whilst someone in Arizona could; it just means the Seattle homeowner would need to buy more solar panels.

A lot depends on where you live. Here are some numbers to consider.

The National Renewable Resource Data Center provides data on average daily insolation levels across the country.

This includes the annual amount of energy received per square meter of ground area and the sunlight information by state and larger cities. 

Once you’ve worked out your hourly usage of electricity (your first step), multiply this number by 1,000 to convert your hourly power generation need into watts.

Divide your average hourly power usage by the number of daily sunniest hours for your area.

(Note: You may need to adjust this calculation if you live in an area where there are fewer than 12 hours).

This tells you how much energy your panels need to generate every hour. So for an average U.S. household (900 kWh/month), in an area that receives five peak sunlight hours per month, it would require 6,000 watts.

Calculating How Many Panels You Need

Now you know your usage, and your average energy received from the sun in your area, you can take your calculated total and put this against solar panel’s specifications when you’re looking to buy!

Once you have found what kind of solar panel meets your needs, you can then divide up your energy usage between the right number of panels. 

As every solar panel converts a very different amount of energy, it would be impossible to just give you a stock number and say ‘that’s what you need’, so it’s up to you to work out your energy usage. 

If you have your kw/hr usage worked out, you can take this calculation to a solar panel specialist or installer and they will be able to tell you exactly what you’ll need to fulfill your energy needs. 

Also, remember that the advertised rate of a panel’s solar yield is based on estimates and testing done in ideal conditions.

In real-life scenarios, they’ll pull a bit less, so it’s wise to fork out for some headroom.

Another Thing To Bear In Mind – Weight

When deciding whether to install a rooftop solar system, knowing the weight of your solar panel system is another important factor to consider.

Be sure to know what your roof can and cannot support weight-wise to avoid a serious mishap.

Knowing the weight of a solar panel is the best way to ensure that your roof can support the full installation.

While panel weights vary greatly from brand to brand, most panels weigh about 35-50 pounds.

Final Thoughts

There are lots of mitigating factors when it comes to deciding how many solar panels you will need.

But, by taking the time to work out your current energy usage and what you can expect to get from the sun in your area, you are setting yourself up with all the information you need to make an informed decision. 

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By Anthony Barnes

Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age