Everything You Need to Know About Solar Battery Backup for Homes
With the recent growth of the home energy storage industry, there has also been a boom in solar batteries. In this article, we’ll discuss what solar batteries do, the different battery types, and their benefits. We will also look at two of the most popular renewable energy storage systems available to homeowners today.
What Are Solar Batteries?
Typically, all storage optionals consist mainly of solar panels and an inverter that turns the 12V DC power into 110V AC power that your appliances can use. Whenever the sun is shining on the solar panel system, energy is produced, but when it’s dark or there’s no sunlight hitting your panels, you will need to rely on the electric grid power.
But, by adding backup power into your system, you can store energy for later use. Your solar panels will charge the battery throughout the day so that even when the sun isn’t shining, you will have solar energy available.
I Already Have Solar, Why Do I Need Batteries?
Besides increased energy independence, there are two main benefits of adding a solar battery into your system: you can save money by avoiding high time-of-use (TOU) rates or demand charges, and you can use your solar energy during grid power outages.
Many utility companies are increasingly switching from a flat rate for energy to time-of-use rates. TOU rates change throughout the day, with the highest rates charged during peak hours – usually late afternoon through early evening, when many people use the most electricity.
These hours are also the times when your solar panels will not be producing much if any electricity and peak rates can be as much as three times higher than off-peak or base rates, so your evening energy usage can still rack up a significant bill.
Avoid Paying High Demand Charges
Demand charges can be assessed in two ways. First is a model that is similar to TOU rates, where you are charged more if you use more energy during peak times, and the second way is that customers are charged higher rates the more energy they use altogether in the month.
However, when a battery is added to your solar energy system, you can control the flow of power for your home and set which hours of the day you will use grid energy, which will use energy directly from your solar panels, and which will use stored energy from your battery.
You can work around the TOU rates by charging your batteries during the day when grid energy is cheap or by using excess energy from your solar panels, and then switch over to battery energy during peak hours to keep your overall costs low.
You also can avoid paying higher demand charges, since a significant portion of your energy will come from your own solar energy system. By storing electricity in your home battery, you can avoid selling excess energy to the grid during the day when rates are low and then potentially buying it back from the grid later in the day for an inflated price.
Emergency Protection During Grid Failures
Finally, a battery allows you to use your solar energy during a grid outage. NEC code dictates that residential grid-tied solar energy systems will be automatically shut down during grid outages to protect linemen as they work on the grid to restore power, effectively rendering your solar panels useless.
However, if you have a solar battery that is charged up at the time the outage occurs, you will be able to use that energy to power your home even while the grid is down. Your panels will not be able to recharge your battery, so you will be limited to the supply of energy in your battery.
What Are the Best Home Solar Batteries?
The Tesla Powerwall and Generac PWRCell are two of the best and most popular home battery systems. Both use lithium-ion batteries and can be scaled up in storage capacity to match the output of your system.
The Tesla Powerwall offers a maximum continuous power rating of 5 kW and a usable capacity of 13.5 kWh. Up to ten Powerwalls can be linked together into a massive 135 kWh battery. Battery power and capacity ratings go hand in hand, since a greater maximum continuous power rating will provide more power more quickly and therefore run through the total capacity quicker. Power dictates which appliances you can run while capacity dictates how long they can run for.
In terms of physical size, each Powerwall unit measures 45.3 by 29.7 by 6.1 inches and weighs 276 pounds. The units can be mounted on the wall or on the floor, either inside or outside. The Powerwall is protected by a 10-year warranty that guarantees a capacity of at least 70% by the end of the warranty period. As with all rechargeable batteries, the Powerwall eventually diminishes in capacity after daily charging and discharging.
The total cost to install one Powerwall unit can range between $10,000 and $16,000, while installing two units will likely be in the neighborhood of $26,000. The Powerwall is a simple, all-in-one AC-coupled system that would be an excellent addition to almost any home solar energy system.
Our team of experts at Power Northwest are certified Powerwall dealers and can assist you with planning what size of battery bank would be best for your system as well as provide a more exact estimate based on your specific project.
Read More: Tesla Powerwall Sizing Chart
The Generac PWRCell is a DC-coupled system that has two separate components: the inverter and the battery cabinet. You can choose from four different sizes of batteries within the cabinet, and combine multiple units into a system that perfectly suits your needs. Depending on the base model you select, the PWRCell offers a maximum continuous power rating of between 3.4 and 6.7 kW. The usable capacity also varies based on the model, from 8.6 to 17.1 kWh.
The inverter measures 24.5 by 19.25 by 8 inches and weighs 62.7 pounds while the battery cabinet is 22 by 10 by 68 inches and can weigh anywhere from 280 to 445 pounds depending on how many battery modules are within. Generac also offers a warranty, but theirs makes no guarantees on the capacity after a set period of time.
Rather, it protects against manufacturing defects and the like for 10 years or until the throughput threshold is reached, whichever comes first. The throughput threshold refers to when a certain amount of power in MWh has been cycled through the battery. The threshold varies based on the size of the battery that you select, from 22.6 to 45.3 MWh.
The smallest PWRCell battery system starts at around $10,000 and the price increases depending on the battery capacity you select. Our solar experts at Power Northwest are also certified Generac dealers and will be more than happy to provide you with a more exact quote and details of the system.
Read More at www.Generac.com/pwr-cell
AC-Coupled vs. DC-Coupled Batteries
The main difference between AC-coupled and DC-coupled battery systems is whether the current flows in only one direction (DC) or rapidly in both directions (AC). DC energy can be converted to AC current using an inverter, but some power is inevitably lost in the conversion. DC-coupled systems are very efficient at charging batteries but less efficient at powering AC appliances, while AC-coupled systems are the opposite. Both systems have their advantages and disadvantages, and our Power Northwest battery technicians can provide specific recommendations for your system.
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