How To Determine If Solar Is Worth It On Your Home

This Is When Solar Power Will Work for You

Tesla and other electric cars require a lot of energy to recharge their batteries. As utility costs rise, many owners are switching to solar power to acquire this energy, boasting about the numerous benefits. For one, they save money by living off the grid. However, solar power has several severe limitations that make it not work for everyone.

Solar power will work for you only under the right circumstances. It requires an ample amount of sunlight to be cost-effective. This requirement makes solar power dependent on local weather conditions as well as how much open access it has to the sky.

There might be ways to work around these restrictions but read below to see if you can meet them before installing solar panels on your roof.

How Solar Power Generates Electricity

All forms of solar power turn sunlight into electricity through some photo-reactive process. Light hits photo-reactive material. As the material reacts, an energy converter turns the energy into electricity. You can then use this electricity immediately, send it to the grid, or store it in a battery.

Photovoltaic Cells

Photovoltaic cells are the simpler of the two categories. The photo-reactive semiconductor elements produce electricity directly. You can build these structures into panels of any shape as only their size and number determine their power output.

Solar Thermal Collectors

Patterned off traditional energy generation, solar thermal plants convert sunlight to electricity through a series of heat exchanges. A photo-reactive fluid flows through a heat cycle by releasing its light-induced heat into a traditional steam electricity generator.

However, they require lots of open space to function. Because of this restriction, solar thermal plants are typically reserved for large industrial complexes and public utilities.

Solar Power Benefits

Whether it is to recharge their Tesla or power their homes, people switch to solar energy for various reasons. These reasons cover the entire spectrum from financial to environmental.

  • Reduce electricity costs: Despite the initial costs, solar power systems pay for themselves quickly in reduced utility bills as they lower your dependency on the grid.
  • Make money: You can sell your excess electricity back to the utility company or directly to your neighbors.
  • Reduce carbon footprint: Solar power requires no fossil fuels to function, nor does it release greenhouse gasses.
  • Reduce fossil fuel dependency: Solar power cells last for years, producing renewable energy that will never run out.

Why Electric Cars Do Not Use Solar Power Directly

With all the benefits and high demand, one might expect the electric car industry to produce vehicles that directly use the technology. Solar electric car races are a thing, and carmakers such as Tesla could easily build the cells into the chassis of their vehicles.

 However, you will not see direct solar power use in commercially available electric vehicles. The racing cars are special builds with low weight, no crash protection, and a single driver, hinting at the reasons for this situation.

Solar power generation is not very efficient. The best available solar panels can produce about 400 watts of power despite being the same size as your average SUV roof. However, even the least power-hungry electric vehicles, such as the Tesla Model 3 or Kia Niro EV, require at least 150,000 to 211,000 watts.

You would need about 400 SUV roofs to power a single electric SUV! Thus, it is more effective to power the charging stations off solar energy than the cars themselves.

Avoid Solar If You Have the Wrong Roof or Location

Regardless of your plans, you need a large enough space with an ample view of the southern sky (or the northern sky for our Southern Hemisphere readers) if you want to go solar. That means you need a large enough south-facing roof or a big enough backyard with nothing obscuring it to the south.

As solar panels are rectangular, your installation location must also be roughly rectangular as well. Only then will you have the sun exposure to reach the maximum output of the cells. Just remember to keep your roof in the best condition possible over the lifespan of the panels.

Your home might have the best spot in town for solar, but you still may not get the benefits of solar power if you live in a region with only a few sunny days. Solar power requires sunlight to function. If you cannot get a consistent exposure, you may see days or months without a single drop of electricity from your array.

If you cannot find a suitable space that will last for 25 years or more, then solar power will not work for you.

When to use Solar Power

In many cases, solar power may not be viable even if you have a good location for it, especially if you have net metering or a time of use plan with your utility.

Luckily, there are a few scenarios where solar will still work wonders for you. You must restrict your heaviest energy uses to daytime activities when the sun is high in the sky, but that is much easier than it sounds. It is also the recommended use strategy for homeowners.

This way, you use solar to reduce your overall energy costs. For instance, you can run your entire home on solar when you are away from home, so you only pay your utility for what you need. Any excess power your system generates will just go to the grid, offsetting your costs even further. Though, how much you will save will depend on the type of utility plan you have.

Net Billing or Metering

Solar power systems reduce your utility bills through one of two different methods. With net billing, your utility buys the electricity from you at the wholesale rate, or the price power plants typically charge. As such, you will not get full price for your excess.

Therefore, you must use your solar power during the day. This is a problem if you might not be home enough to get the most out of your system during these hours. You might be at work and therefore nowhere near your house to use your charger and appliances.  

If you want to truly live off solar power, you need to ensure that you are on a net metering plan. Under this plan, the utility buys all your excess, letting you receive free or reduced-cost electricity off the grid when you need it.

Time of Use Billing Plans

Time of Use (TOU) billing means you pay for the electricity you use when you use it. Generally, TOU plans charge more during evenings and night when you use more power than during the day. Unfortunately, this means you often pay more when solar energy is not highly effective.

Luckily, if your solar cells produce enough excess during the day, you can cut your TOU peak rates. You must ensure your solar sales are always working at peak performance to reap this benefit though.

Make Sure Solar Power Will Meet Your Needs

Any power generator you use must produce enough power to run all your devices and then some. Solar power is no good to you if it cannot even let you turn the lights on. Therefore, you want to calculate your daily energy use.

Most devices post their wattage somewhere on them or in their user’s manual. Therefore, you should be able to determine your energy needs very quickly. You just add up all the values you expect and want to run at the same time.

Calculating Electric Car and Charger Electricity Usage

Your electric car charger requires a more complicated calculation. However, it is still simple enough if you know how far you travel in a day as well as your vehicle’s electric fuel economy.  Finally, you must also consider your charger’s efficiency, which is about 15 percent for most models.

Once you gather all this information, you just use the following formulas to find how much energy you need to power your car. For instance, if you drive your Tesla Model 3 forty miles every day, your energy usage would be 11.96 kilowatts.

Calculate the Size and Number of Required Solar Panels

As the average Tesla car requires about 12 kilowatt-hours of energy per day, your solar array must produce at least that much if you expect it to work for you. You need a bit more to include your other devices as well.

Luckily, most solar systems are modular. You can always create one that can cover your energy consumption in theory. However, this might not always be the case in practice as you may not have enough available usable space. Other important factors include the:

  • Shape of your roof
  • Local climate
  • Efficiency of your panels

It requires a bit of math, but it is doable if you are willing to do the work. You can also let one of the many online solar power calculators do the work for you.

Using an Online Calculator

Most solar energy providers offer a solar panel calculator for assessing their products. You can also find a few standalone calculators around the internet as well. Each one does the same thing. They provide an estimate for the solar system size and wattage you need to power your devices over a given month.

Please note that these calculators only give you results for the ideal case of an unobscured medium-slopped, south-facing roof on a hot sunny day in the middle of summer. For instance, these sites may give you a quote for a 2.26-kilowatt system with 6 to 9 panels for a home in Beverly Hills, California.

The estimates will vary between location and roof orientation, but they are relatively constant over a given town. That 2.26-kilowatt rating works for most homes within the Los Angeles area.

Other standard solar system configurations for Tesla Model 3include:

  • Seattle, Washington: 8–13 solar panels
  • Kansas City, Missouri: 6–10 solar panels
  • Miami, Florida: 6-9 solar panels
  • Phoenix, Arizona:  –8 solar panels

Required System Size for a Solar-Only Lifestyle

The above values are only useful if you plan on using solar power to offset your utility usage. If you plan on going entirely off the grid, you need a much larger setup. You need a system that can produce enough energy to power every device you have, charge your car, and still have enough left over for emergencies.

The energy output you need will vary based on the type of devices you have and your vehicle’s charger type and capacity. Like in the previous cases, you must add up all their power ratings to get your daily energy consumption.

You can then compare it to the 1,500-watt average you can get off a typical household outlet, often called level 1 charging. Just remember that if you have a dedicated 240-volt level 2 charger for your vehicle, you will have a much higher power requirement.

For instance, a typical Tesla vehicle with a level 2 charger requires about 31,000 watts of power from an array containing 80 400-watt solar panels operating at 75 percent efficiency.  

Location, Location, Location

All the values we used in this article presumes an ideal location and climate. Any trees blocking the panels and inclement weather can render any solar power plan mute. Therefore, you must check to see if you have the space for the array you need. You may also want a backup system if your area gets frequent storms.

If your roof is not big enough, you can still use solar power if you can place the panels in your backyard. The panels just need a direct line to the sun. They do not care where you put them. This scenario requires that your backyard is big enough, but it is an option if you want to go fully solar.

The problem is compounded by most utilities restricting residential solar setups to 25 kilowatts or lower. Luckily, the average home system outputs less than 10 kilowatts. You have some leeway, but you may need more panels than you think to reach your solar goals.

Remember also that these values are only for your car. You must still have enough power left over for your appliances and other devices. An extensive photovoltaic system can help, but you still need to rely on your utility company if your car requires an 11.5-kilowatt charger.

Make Sure You Have Enough Batteries

No big home solar power play will be complete without a similarly large battery to go with it. Your solar panels can only produce electricity during the day, and the batteries can help offset your daily real-time energy needs. However, solar batteries are often as expensive as the solar cell array itself.

Just make sure you have the batteries to keep up with your demand. The average daily energy consumption for the electricity is about as much as most Tesla Powerwall configurations can output in a day, and that is with the grid acting as backup. You may two Powerwalls just for your car and pay the $14,100 asking price to Tesla for the privilege.

Futureproof Your Solar Power System

To reap a return on your investment, you might be using the same solar array with several generations of electric vehicles. That means your array must produce enough energy to handle anything the industry might throw at it.

As electric car technology advances, the vehicles will continue to require more and more energy. You may also end up owning a second electric car as well. Add in our growing dependency on electronic devices, and you have a recipe for disaster if you never considered your future consumption in your solar design.

To that end, you may want to use microinverters instead of the traditional string inverter. Microinverters make your system modular, so you can just add panels if you need them. But make sure you have the space for your extended array, such as a new section of your roof.

Most People Should Not Go Solar Only

With the added expanse and configuration challenges, most people should not switch entirely to solar. Most homes are not large enough to fit all the panels, and the right systems are often too expensive and impractical. You may achieve a fully off-grid-lifestyle, but you will most likely lose your backyard in the process and the finances to enjoy it.

Instead, you should plan on mixing your energy from solar and your local utility and find the most economical balance for you. You can charge your car based on your utility plan for the best rates and leave your solar system for your other devices.

Any electricity you sell back to your utility company will offset your costs, letting you reap the benefits of solar without strain on your wallet.


Solar power is taking the world by storm, but it might not be the right energy source for you. Sure, you can reap numerous benefits from it, but you must have the right conditions to see those benefits. By understanding your energy needs and the sun available in your location, you can know if solar power will work for you or not.

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The articles here on are created by Greg, a Tesla vehicle and Tesla solar expert with nearly half a decade of hands-on experience. The information on this site is fact-checked and tested in-person to ensure the best possible level of accuracy.

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