Solar Home Battery     

Home Energy Backup & Storage Solution

   Home Solar Batteries are your answer to energy independence and total control of your power for your home. If there was ever a blackout, you are covered knowing that your food won't go bad, that you have the internet to do work (and keep the kids occupied), as well as having lights to get you through the night. 

   Our Home Solar Battery Options pair with our Peace of Mind Policy. Just like our 25 year bumper to bumper warranty giving you peace of mind knowing your solar system is covered for 25 years, our Home Solar Battery Options give homeowners the peace of mind knowing that they can be self-sufficient and independent when the utility chooses to cut their power. 

   This article talks about how batteries work, the differences between them, and most importantly how they can benefit you and put money back in your pocket. For any questions on batteries or anything solar related call 925-289-8966 or email ktrue@kotanenergygroup.com

 History of Solar Home Batteries 

Traditionally, a solar storage battery was a lead-acid battery bank hooked up to an off-grid solar battery charger and battery inverter. The batteries, battery charger, and battery inverter were separate. These were a stable technology but they are big and heavy, and only last for a long period when the depth of discharge is limited to 40-50% of the batteries' capacity.
 

The newer solar battery technology that is now taking over is Lithium-ion (Li-ion) solar batteries, the same battery chemistry as exists in cell phone batteries and computer batteries. The advantages of Li-ion batteries are that they can be discharged to almost 100% of their total storage capacity and they have greater energy density per square foot and per pound of weight.

 How Solar Home Batteries Work? 

Batteries are pretty straight forward in terms of how they work. The animation to the right can help explain the process.

 

In general, the solar panels on your roof take in the sunlight and transforms it into DC power.

 

The DC power is converted to AC in your grid-connected inverter, then it is converted into your battery inverter and that power is stored into the solar battery as DC power.

 

And when the power is needed, the battery inverter converts the DC power from the battery back into AC power and supplies it to the home to use. 

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 Power Rating vs Capacity Rating 

The batteries have two ratings

 Capacity Rating and Power Rating

Understanding how these affect your battery will help you understand which battery option is the right choice for you.


Capacity Rating (kwh) - is the total amount of electricity that a solar battery can store, measured in kilowatt-hours (kWh). 
Power Rating (Kw) - is the amount of electricity that a battery can deliver at one time. It is measured in kilowatts (kW). 


Understanding Capacity & Power Ratings


A helpful analogy is the water canteen in the desert example. In the desert, you want to conserve as much water as you can and only use it when you need it, same goes for the lithium in the home backup batteries. The size of the canteen holding the water is like the capacity of the battery - its how much it can store. While the mouthpiece size is the power rating - it's how much can be delivered at one time. 

 

 

 

 


A battery with a high capacity and a low power rating would deliver a low amount of electricity (enough to run a few crucial appliances) for a long time. A battery with low capacity and a high power rating could run your entire home, but only for a few hours. 

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Power Rating 

Capacity Rating

 Why Get A Solar Home Battery? 

Having the lights on at your home when your neighborhood is hit by a power outage has a value that can’t be expressed in terms of money, which explains why some folks have been willing to pay thousands of dollars to add batteries to their home. But there are other benefits of home energy storage that can be quantified.

Save with Solar Self-Consumption

  One of those benefits is ensuring that you’re the end-user of all the solar energy your system produces.

  Numerous states across the U.S. offer Net Metering (NEM) when you go solar. Under NEM the utility is giving you the retail rate for everything your solar panels produce. It's a one for one credit and if you have excess credits they can be carried over each month.

 

  Now once per year your bill will "True-Up" showing if you have overproduced or underproduced for the year. If your system overproduced, the utility is paying you pennies on the dollar back for that power around 3¢/kwh. However, if your system underproduced, you have to pay the utility the Baseline rate (~24¢/kw) for all that you couldn't produce yourself. 

  So what does NEM have to do with batteries? If you are smart about your usage during an outage you will be able to reduce the number of credits you pull from the grid to power your home. Powering your home's necessities from the panels and not from the grid allows you to bank your own credits without having to rely on the utility, which ultimately results in a reduced ROI and being completely self-sufficient.

 

Save By Taking Advantage Of Time-Of-Use "& "Dumping"

  The second way you save money with a home battery is by avoiding the high cost of on-peak electricity under a time-of-use (TOU) billing plan


  On a TOU billing plan, electricity is cheap when most people aren’t using it (i.e. nights and weekends), and more expensive when they are. Most TOU plans charge the highest prices during the afternoon and evening hours, when people are cook, watch TV, and wash and dry their clothes. Oftentimes, TOU rates vary by season, with higher prices and longer peak hours in the summer when air conditioning causes extra-high spikes in energy usage. 

 

Here’s an example of how TOU works using past rates from Southern California Edison’s TOU-D-B schedule (subject to change, of course):

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  You can save money with a home battery by setting it up to charge only from electricity produced by your panels or from both the panels and the grid. In either case, the key is to discharge or "dump" the battery when electricity is the most expensive.

  By completely removing your on-peak use, you’re effectively bringing your electricity rates down, to as low as off-peak prices if you can swing it.Using the rate in the image to the right, you can charge the battery for $.13/kWh and discharge it when you would have spent $.33/kWh, you’re saving $.20/kWh during peak times, every day.

 Long Term & Temporary Backups 

Or maybe you’ve got solar panels pumping electricity out to the grid during the sunniest hours of that peak time, meaning you’re earning that $.33/kWh for your energy, even as your battery meets your home’s energy needs. In the industry, this process is often referred to as battery "dumping" or "peak-shaving" because you are charging your battery with cheap energy and "dumping" it when energy is expensive so you are ​shaving off the peak prices to help put more money back in your pocket and cut down on the ROI of your total solar system price. 

Temporary Backup

The temporary backup battery option is a good, cheaper option for homeowners looking to only have enough power for a limited power outage. It is only as good as what is in the battery at the time of the outage.  If you have a full battery (regardless if it's filled from the grid or the solar panels), once the power goes out all you can use is what's in the battery without being able to be recharged until the power outage is over. 

Long Term Backup

The long term backup is the best option for any and all power outages, but with the best comes a higher price than the temporary backup option. The long term backup allows you to use your battery during power outages, and refill it with solar power during the day for a continuous supply. So, no matter the duration of the power outage, as long as the sun keeps coming up (which its been steadily coming up for a couple of million years 😅) you will have the energy to power your home. 
 

 Battery Options Available 

We have access to any and all batteries on the market, and if there is a battery you are looking at specifically just let us know. Although we have open access to all battery options the two market leaders we advise for the majority of homeowners looking for a solar home battery option are the LG Chem RESU and the Tesla Powerwall 2

    The home electronics giant, LG, has recently entered the American solar battery backup market space with LG Chem. LG Chem is an energy storage device that uses a lithium-ion RESU battery.

    This battery can work both as backup power as well as a tool that maximizes solar energy consumption in residential areas. LG Chem comes in a variety of sizes, i.e., from 2.93 kilowatt-hours to 12.4 kilowatt-hours. The market leader is hands down the LG Chem RESU10H because of its level of efficiency. It has a 5kw continuous power rating meaning it can supply 5kw of continuous power. It also has a 9.8kw capacity rating which is more than enough to power what you need for a power outage. 

 LG Chem RESU 

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 Tesla Powerwall 2 

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   In April 2015, automaker Tesla forayed into the home energy storage market with the Tesla Powerwall. The company has since launched many updates on its first version. Tesla defines its Powerwall as a rechargeable lithium-ion battery that supports liquid thermal control.

  As with the other sectors the company has forayed into, the company also managed to rebrand the residential-use batteries sector with the Tesla Powerwall. Tesla Powerwall comes with an unlimited 10-year warranty. However, Tesla Powerwall is a pricey solar battery backup, and it will quickly set homeowners back by $8,500 to $16,000. This figure includes the price of the device as well as the installation costs. To see how much a Tesla Powerwall would cost for your home click here

The Difference Between

Tesla Powerwall 2 and LG Chem RESU Batteries

   Both the batteries support a power rating of 5 kW and a maximum peak of 7 kW. However, LG Chem wins in the area of round trip efficiency. In comparison to Tesla, which claims 89% round trip efficiency, LG Chem claims 96% round-trip efficiency. While both the batteries come with a 10-year warranty, LG Chem comes with a 60% retained capacity warranty. Tesla Powerwall, on the other hand, comes with a 70% retained capacity warranty, a percentage that matches the performance estimate of the other solar battery backup options available in the market. The chart below details the differences in the various battery options on the market. 

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Looking to get a solar battery for your home? Start off by using this solar battery calculator to the right to determine what appliances you'd want to run during an outage and the power needed to make the right battery choice.

The "necessity appliances" are most often the fridge, internet, some lights, electronics chargers, and/or washer/dryer. When using the calculator the kW rating can't exceed the continuous power rating (i.e. LG Chem RESU 10H = 5kW). If you exceed the kW rating then an additional battery is necessary. 

For more details be sure to check out our FAQ page that has all the answers in detail to all of your battery-related questions and more, or call or email for personal assistance. 

 Find the Right Battery For Your Home 
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9252898966

ktrue@kotasolar.com

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