• Solar Battery Backup

    The facts you need to know before you make the investment & battery offerings from SunPower by Stellar Solar


    "Get off the Grid."  "Keep your home powered during a blackout."  "Power your home through the night."  “Offset the upcoming Time of Use changes.” “Free battery with the purchase of a solar system.” These are the promises of the solar battery (and some local installers) and while they are all somewhat true statements, there are many factors to consider before you purchase a solar battery to complement your solar system. SunPower by Stellar Solar has several options available for homeowners where batteries make sense but we also want to make sure you are fully educated before you make this investment.  

    Get off the Grid

    For those of you who are serious about getting off the grid, yes, solar batteries can be an option but the number of batteries needed to make this viable could prove to be cost prohibitive for most. Where the batteries start to make more sense is on fully "off-grid" homes that are simply too expensive to send power to, or that are far enough from the grid that outages are frequent.  

    Overnight Power & Power Outages 

    As far as powering your home through the night, this is when electricity is at it’s least expensive and at this early stage of the battery game, might not be worth the investment. Let's take the Tesla Powerwall for an example.  The battery is marketed as a backup system that supports 14kWh per battery and costs $6,200 without installation.  Installation of the battery alone costs anywhere from $800 - $2,000.  Tesla suggests that for any home bigger than 3 bedrooms, two batteries are required.  So with two batteries plus installation, you are looking at a $14,000+ cost, without panels.

    Beyond the cost, the other problem with these batteries is that their capacity is simply not enough to be considered full "backup".  A 14kWh battery is only large enough to power a 3 bedroom house’s essential load circuits part of the way through the night.  If there is a power outage, there is not enough capacity for the battery to be considered in the same category as a generator.   Also, seeing as how the average US home only loses power for two hours a year, the selling point that you need this battery for backup just doesn't hold up.

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  • Time of Use Changes

    In 2018, a new rule went into effect with SDG&E where everyone who goes solar has to use a Time of Use energy rate structure.  Time of Use Rate structures charge you different amounts for electricity depending what time slot in the day you are using it.  Under this new rate structure, electricity will be most expensive during the evening hours: 4-9PM.  If you have a solar battery, you can store the extra energy you create during the day to be used during this time.  This allows you to offset that high rate when you are using the most energy, so you can use your appliances during peak times with no worries.    

    Free Battery with Solar Purchase

    In San Diego, several local companies advertise a “free battery” with the purchase of a solar system.  This is deceptive, as they are just working the cost of the battery in somewhere else, to make it appear that you are not paying for the battery.  This is nothting more than slick marketing as there is no possible way those companies can absorb the cost and give away a battery.  We urge you to compare the quotes of the companies that make these claims to other installers.