Solar Battery Backup Systems Off Grid or Grid Tied

Solar battery backup systems are a cost effective way to provide electricity to power the essential circuits in your home or office independent from grid power.  When the grid is down, your protected loads like refrigeration, lights in critical areas, communications and medical devices operate from your solar energy stored in batteries.  Your battery backup system can be totally independent from the grid, or may also be grid tied.  Either way, your utility bill will be reduced and your important circuits operational.

Off Grid Solar Battery Backup Grid Independent

A grid independent system provides backup or uninterruptable battery produced alternating current or direct current to operate your important electrical circuits like computers,  lights and appliances in the event of a loss of grid power.  These electrical loads can be operated from your off grid system and reduce your utility expense.

Off Grid Solar Battery Backup Grid Tied

Some utilities will allow your off grid battery backup system to also be grid tied so that when you are not using all of the energy that is available it can be used to reduce your electric bill.

What We Need to Know to Size Your System

Your Critical Loads

  • What circuits (electrical loads) do you need to operate when the grid is down?

  • How many hours do you need these circuits to operate?

  • For appliances, look at the Energy Star appliance power requirements.

  • What are the peak load (watts) for all of the circuits and devices may be run simultaneously?

  • What is the voltage required (120 vs. 240 VAC)

  • How may days of backup do you require?

  • Are outages in your area likely to be accompanied by long periods of inclement cloudy weather?

Things to Consider

  • Refrigerators, freezers, lights in important areas, ventilation, TV, radio, computer, cell phone charger, alarms and medical devices are the most essential loads to consider.

  • Heating systems vary widely and may or may not be practical to operate.

  • Air handlers on furnaces can be very large energy loads, even if the heat source is gas.

  • Inductive loads like electric stoves, heaters, electric water heaters require 240 VAC and are high energy users

  • The larger the loads and the longer they run, the more expensive the system will be.

  • Do you have or can you add a generator if the backup needs to be larger or last longer?

  • A protected loads panel is far more convenient and cost-effective than whole-house backup.

  • Accurate load analysis is worth the time and will result in a more cost effective investment and operating performance that meets your needs.

We used to be able to assume that power outages are a rare event.  The truth is that in 2008 the majority of grid failures were caused by faulty equipment, human error and judgment or animals, not major disasters. More recently global warming is driving more frequent and intense storms that have had widespread disastrous consequences leaving millions of homes at a time without power.  A solar powered battery backup system will keep you and your loved ones prepared and safe should the power fail.

Typical Solar Battery Backup System Sizes

  • 3,600 watts peak load at 115 VAC

    • 12 each 250 watt 24 volt solar panels

    • 405 amp battery bank at 24 volts DC

    • Enough energy to operate a refrigerator, freezer 24/7 and lights and other limited use loads

    • Reference price about $18,000

    • A system like this can be upsized by increasing the battery bank voltage and number of solar panels to 15-18 modules, the system will be limited to 115 VAC loads only

  • 8,000 watts peak load at 115/230 VAC 40 amps peak at 230 volts

    • Up to 30 each 250 watt 24 volt solar panels

    • 1,215 amp battery bank at 48 volts DC

    • Enough energy to operate a small house with limited 230 VAC loads

    • Reference price about $34,000

    • A system like this can be upsized by adding one or more additional inverters, increasing the battery bank size and number of solar panels

    An Outback Power Flexpower One system that meets the requirements of a 3,500 watt 115 VAC system. The system comes prewired on a back board. Hang on the wall and start wiring.  The battery bank is 8 each Sun Xtender 405 amp 6 volt batteries wired 4 in series two strings parallel to make 910 amps at 24 volts.  Photo courtesy of Juan Wilson in Hanapepe, Hawaii.  Visit Juan's website

    Take the Next Step

    Read our Successful Off Grid Solar Design download which tells you much of what you need to know to size your system.

    Please contact us today for assistance.  If you have not done your load calculations there won't be much to discuss.  It all starts with knowing your loads.  If you have questions or need assistance, we are ready to help.