How many solar panels to charge a Tesla Powerwall?

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Calculation and thought must enter installing a solar panel system to charge a Tesla Powerwall home battery.

To fully charge a Tesla battery, which has a capacity of 13.5 kWh, solar panels must generate at least 15 kWh, accounting for energy lost throughout the charging process. The number of solar panels needed will vary depending on how much electricity a home uses, with more panels required to handle both night-time usage and Powerwall charging.

To precisely calculate electricity usage and establish the required solar panel system size, obtaining professional guidance and utilising a digital electricity meter is advised. A system of at least 10 kW is typically recommended for charging a Tesla battery and meeting daytime electrical needs.

How large of a solar system do I need to charge a Tesla Powerwall?

The straightforward answer is that the more solar panels you install on your roof, the better. Generating extra solar power on your roof and selling it back to the grid at a low price is the best option. This is better than not having enough solar power to effectively charge your Tesla Powerwall or other battery.

In many cases, as well as our example, the Tesla Powerwall will be used close to its full capacity of 13.5kWh daily. So if you do not need that much solar battery capacity, the Tesla Powerwall may not be the best option for your home.

A Powerwall has a usable capacity of 13.5kWh of electricity with a round trip efficiency of 90%. Yet, this implies a 10% loss of electricity during its transfer in and out of the battery.

The solar panels need to generate 15 kWh of electricity for the battery to store 13.5 kWh. This means that the panels must produce more electricity than the battery can hold. The excess electricity generated will be used to power other devices or be stored for later use. Generating more electricity ensures that the battery system will always have enough power to operate efficiently.

So one should allow at least 15kwh of additional generation from your solar panels to charge the Tesla Powerwall.

Professional advice will help you work out your needs

When deciding on the right size for your solar panel system, companies often use the average yearly power generation of solar panels. If you want to produce an extra 15 kilowatt-hours (kWh) of electricity each day, you might need about 3.5 kilowatts (kW) more in solar panels. This extra amount is to cover your home’s electricity use during the daytime.

Let’s make this easier with an example: imagine a family using a total of 28 kWh of electricity in a day. Around 15 kWh is used during the daytime, and the rest is used in the evening and at night.

To meet these needs, it is suggested to have a 3.5kW solar system for daytime power. Another 3.5kW system is recommended for storing electricity to use in the evening and at night. So, for this example, a total of 7kW in solar panels is recommended.

This approach ensures your solar setup is the right size to meet your daytime and night-time electricity needs. For personalised advice, it’s a good idea to talk to a trusted solar company. They can guide you to the best system size, making sure your home gets efficient and cost-effective energy.

Does this calculation cover the whole year?

We have a detailed output calculator on this website to see how many kW of solar system capacity one would need in which Australian postcode, as sun irradiance (intensity) and solar system output vary across Australia. This will allow you to determine your specific requirements at your location.

The above calculation is based on the average generation over a year. The solar panels will produce less than half the average on a mid-winter day than in mid-summer.

The panels do not produce sufficient electricity to fully charge the battery for 3 to 5 months during a typical day. This means that there may be periods when the battery is not fully charged. This usually occurs during certain months of the year. So in this instance, grid power must be used to fill the battery for the missing kW.

To make sure your Tesla Powerwall stays charged and costs less all year, it’s important to double the capacity of your solar panels. So, to fully charge the Powerwall, consider installing at least 7kW of panels.

Remember, this suggestion is just for keeping the Tesla Powerwall charged throughout the year. It doesn’t include the panels you might need to power your home during the day.

Talking to a solar company for advice on your solar setup is a good idea. This will help ensure that it meets your needs and charges your Tesla Powerwall effectively.

Consulting with experts can help you make informed decisions about your solar energy system. They can help create a system that works well for your home and helps you save on energy costs.

Tesla powerwall on wall
Tesla’s Powerwall has a high capacity, meaning a high energy input from panels is essential

Adding battery requirement and daytime consumption

Therefore, the panel capacity required to power the home’s electricity use needs to be added to this.

If you have a digital electricity meter, the best way to do this is to ask your solar company to organise a report showing your energy usage for the last 6 or 12 months, which will also allow you to work out your day and night electricity consumption.

From this, you can accurately calculate how much electricity you use daily and design your solar system accordingly. Our sample assumes the daily consumption requires 3- 3.5kW of panels.

When we add the sizing for self-consumption (3-3.5kW) with sizing to charge a Tesla Powerwall (7kW), we will get an ideal solar system size of 10kW or even a bit more significant in inverter solution and solar panels.

More solar panels mean more peace of mind for your Tesla Powerwall

Choosing solar panels for your home is a great idea, and while it’s often recommended to go for a bigger system, it’s also okay to consider a smaller one. Even with a smaller setup, you can efficiently charge your Tesla Powerwall using the grid, especially when electricity is cheaper.

For a smooth transition to solar energy, it’s a good idea to get help from a trustworthy solar company. They can design a solar panel system that fits your needs and takes into account changes in sunlight during different seasons, making sure your home gets reliable energy all year.

When you work with quality experts, you can trust that your solar system will be customised to your needs. This will give your home the best energy results. Switching to solar power is easier with a personalised plan that meets your needs. This plan can help create a more eco-friendly and affordable energy future.

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