Solar battery storage

Battery storage helps you get the most out of your solar energy system. It’s important to know your options and alternatives when it comes to solar battery storage.

How solar battery storage works

Solar panels combined with lithium batteries put you in control of your own power supply. Whether you’re wanting to make your home self-powered, or you’re seeking freedom from power outages, you’ll be covered day and night with solar battery backup. This image shows an average day looks with solar battery storage.

Graph - How solar batteries work

Self-Powered Mode

Solar Panels

8 AM to 5 PM. The day begins and the sun rises as always. Your solar panels provide energy to your home and charge your batteries from the night before. Most times of year, this energy is more than enough to completely power your home all day until sunset. Any energy not used goes back to the utility grid for net metering credit.

Battery Storage

5 PM to 8 AM. As the sun sets into darkness, your home battery takes over but you won’t notice any difference. The battery utilizes the stored solar energy that you made during the daytime and powers your home without any supplementary power from the grid. Your house has become self-powered.

Utility Grid

Utility Back up. If you need more power than your batteries can provide, your utility will provide the rest of the energy you need. This is common during the wintertime when the sun is at its weakest or on days when you have a higher demand for energy. You’ll use any energy credits that you have accrued from the utility, or the energy will be billed to you at low time-of-use rates. The next day the sun will always be there to recharge the battery.

Emergency Backup

In the event of a planned or unplanned utility outage, your solar battery system will automatically switch to backup mode. In this mode, your solar panels and batteries will continue to work and you will continue to have power, unlike a simple stand-alone solar energy system without batteries. Without batteries, a solar energy system during a power outage is required by law to shut down leaving you without any power at all.

Why have solar battery storage?

Energy storage systems are an exciting new technology that is developing quickly in the solar industry. With the cost of storage dropping significantly over the years, batteries can help customers save money over time. But the greatest benefit is the peace of mind that backup power offers when the grid goes down.

Own your own power plant

Solar battery systems are automated, compact sources of stored energy and reduce a homeowner’s dependence on the utility grid.

Get net zero

Combine solar panels and one or more home batteries to power a home independently from the utility grid. Net zero energy means that a home produces as much energy as it consumes, but is still connected to the utility grid if needed.

Solar electricity at night

Electricity generated by solar panels during the day is stored in batteries and available to your home in the evening. This bridges the gap between peak solar and peak demand.

Guard against power outages

Never be unprepared for a planned or unplanned power outage again. Your solar batteries are a safe and reliable back up against the risk of power loss.

Solar Battery Storage Frequently Asked Questions

This depends greatly on uncontrollable factors like weather and energy usage habits. A small, highly efficient home with energy efficient appliances might power more than a larger, older home with inefficient appliances and lights. By monitoring your energy usage, you’ll gain greater insight into what you can power and how quickly your battery might recharge.


To determine what’s best for you, Rooftop can take a look at your average historic energy consumption and discuss your goals for battery storage .It’s all about the give and take when it comes to planning out your home battery storage solution. Many large appliances, such as most electric heaters and heat pumps, use too much power to realistically back up. A more realistic expectation is to back up less energy-intensive loads, such as lights and electronics, refrigeration, wall outlets, pumps and fans; and only loads that are critical or necessary.


To determine your home’s energy loads, buy a home energy analyzer OR contact Rooftop Solar today.

A self-powered home combines solar energy and a battery to independently power your home day and night. During the day, solar panels may produce more energy than your home uses. Your battery stores that excess solar energy and makes it available to your home even after the sun has set. Through an app, you will have full visibility into your self-powered home showing solar production, battery status and home energy consumption.

The solar battery can detect an outage, disconnect from the grid, and automatically restore power to your home in a fraction of a second. You will not even notice that the power went out. Your lights and appliances will continue to run without interruption. Solar energy will continue to power your home and recharge the battery. Without the battery, solar will shut down during an outage.

It is different on a site-to-site basis and based on a personal preference. Most homes will need 2 or 3 batteries, unless your home is extremely energy-efficient. An average home consumes about 28 kWh per day, which means an average house would need two Tesla Powerwall 2 batteries to supply a day’s worth of regular energy consumption. The total number of batteries you need is a personal choice depending on how much power you want or need to store and what types of devices you hope to switch on during a grid outage. Each system is fully customized to maximize the homeowner’s financial benefit and to reach their goals. To get a full picture of how many batteries you might need, contact Rooftop Solar about your objectives and review your energy usage history.

This is another question that’s hard to answer. It really depends on the weather, brightness, shading, and outside temperature. In perfect conditions with no loads and a maximum 7.6kW of solar power, a Tesla Powerwall 2 could charge in 2 hours.

AC battery systems (such as the Tesla Powerwall 2) are able to be retrofitted to homes with an existing solar installation, but they are slightly less efficient compared to the common DC battery systems. This is due to losses in the conversion from DC to AC power, first the DC solar energy is converted to AC by the solar inverter, then back to DC to be stored in the battery and finally back to AC when it is needed by the appliances (with typically 3-5% losses in each conversion). This adds up to approximately 89% round trip efficiency compared to around 95% efficiency with a DC coupled battery (such as a LG Chem).

AC battery systems require a separate solar inverter for the solar panels. DC battery systems use the same inverter as the solar panels. Rooftop Solar can help you choose the battery system that is right for your house.

An AC battery system is only designed to operate in off-grid (back-up energy) mode for short durations (until the battery is depleted) and is not designed to function as an dedicated off-grid power system. If you are looking for a true off-grid battery system, Rooftop Solar can design a custom system specifically for off-grid applications

Your solar battery system will operate if the utility grid goes down, and your home will automatically switch over to the batteries. If the sun is shining when the grid goes down, your solar panels will continue to charge your batteries and stop sending any energy back to the grid. The unit that relays power from your system to the batteries isolates all the power in the house from the grid. This ensures the safety of line workers and is an automatic process when the grid goes out.

Battery systems are eligible for the 30% solar tax credit when it is installed with solar. Your utility may have additional incentives as well.

The batteries can be installed indoors or outdoors and can operate within a wide range of temperatures. At the extremes of the temperature range, your battery may limit charge or discharge power to improve battery lifespan. If you are in an area that is often outside of the 32°F to 86°F range, we recommend that the batteries are installed indoors. To optimize performance, avoid installing batteries in locations exposed to direct sunlight or subject to extreme temperatures. Additionally, while humidity and rain do not pose a risk, batteries should not be installed in locations subject to flooding or near water sources such as downspouts, faucets or sprinkler systems. In order to maintain proper ventilation, batteries should be kept clear of debris such as leaves and dense brush, and areas of accumulated snow. Batteries should not be installed in habitable areas or on external walls of bedrooms. While they are fairly quiet, they do emit low level noise and vibrations.

Find out if solar makes sense for you

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