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How Big of a Battery Backup Do I Need for Solar In El Cajon?

Solar power generation has accelerated during the last several years and shows no signs of slowing. By 2027, it is poised to surpass coal as the largest energy source in the world.

This is due in part to innovations in solar panel efficiency and storage capacity. This latter development is one of the main factors driving residential solar installation: the ability to make use of the power generator even when the sun is not shining.

Determining how big a solar battery backup you need is important. You want ample capacity without going overboard.

Calculating solar battery backup for homes in El Cajon depends on several different factors. This article explains what those are, so you can make the best choice based on your unique energy needs. 

Daily Energy Consumption

One of the biggest factors in determining the needed solar battery backup size is daily energy consumption. You should be able to find this information on your existing energy bill. It is most often reported in kilowatt-hours (kWh).

Divide this number by 30 (approximate days in a month) and multiply it by 1,000. This will give you how many watts of power are sustained over one hour.

Solar System Generating Capacity

Next, you need to consider how much energy your solar panel system (if you already have one) will generate in a day. This is based on the size and type of solar panels you have, as well as the number of sunny days where you live. Subtract your daily energy consumption from the average amount of power generation your system puts out on any given day.

El Cajon averages about 260 sunny days per year, far above the national average. This means there are less than 100 days every year when your full solar generating capacity may not be reached.

Days of Backup

The size battery you need is also affected by how many days of backup you desire. If you only plan to rely on backup batteries overnight, then a smaller battery will be sufficient. For longer stretches, such as several cloudy days, then a larger battery will be warranted.

Battery Type

Finally, there are many different types of solar battery backup El Cajon has to offer. Flooded and sealed lead acid batteries are inexpensive, but they require a lot of maintenance and ventilation. They also only last between three and seven years.

Lithium-ion are some of the best batteries for solar power storage. They will last 10 years or more, with no maintenance or venting required. They also charge faster, are more efficient, and have greater usable capacity, or "discharge depth."

Learn More About Solar Battery Backup Sizing

Now that you understand how solar battery backup power works, you can determine the right size and configuration for your energy needs. A solar panel expert can further advise you on the best batteries for solar power storage.

Semper Solaris is inspired by the Marine Corps motto, "Semper Fidelis," or "always faithful." We bring that same level of dedication and pride to the services and products we provide to our clients. Get a free quote on solar panels for your home, including battery backup installation, today!

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*Minimum purchase required. New customers only, Solar and Battery discounts cannot be combined. Batteries must include backup, and be 10kWh or larger. HVAC must be complete change out or two head mini split. Roofing must be a minimum 1600 sqft. Minimum solar system size required typically 10 panels or larger. Speak with your sales rep for complete details. **On approved credit. 30 percent federal tax credit based on eligibility, consult your tax advisor. ***Savings based on size of roof. Cool Roof upgrade with roof replacement only. †Must purchase a complete heating system. ‡Present this at the time of your appointment. §Unlimited referrals accepted. Maximum awarded amount per new customer is $550 for referrals that purchase. Referral name must be supplied by referrer, referral amount paid after completion of the installation and payment.

FOR ALL OFFERS: New customers only, some restrictions apply. Cannot be combined with other offers. See here for more information on warranties. Offer Expires 05/31/25.

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