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Do I need battery backup for my solar panels/system?

asked 2014-08-05 12:05:22 -0700

puneet.s gravatar image

updated 2014-08-05 16:15:17 -0700

manvendu gravatar image

As batteries will increase the monetary value of investment in the Solar system, is it required to use batteries? If not, then how to make a continuous power supply for house under any failure in Solar PV System?

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answered 2014-08-06 16:17:20 -0700

manu.bhardwaj.52012 gravatar image

The short answer is you don't have to use batteries with your solar energy system. It all depends on what you are trying to achieve with the system installation in your house. A couple of scenarios can be:

  • Use the system to provide backup power in case of power-cuts and store all the electricity produced by the solar system : In this case you do need batteries. A very simplistic way to estimate the amount of battery backup can be

Amount of Battery backup needed (KWH) = Average hours of power cuts per day (hours) x Electric load you are looking to handle during the power cut (KW)

However, the total backup should not exceed the total amount of energy (KWH) produced by your installed system. As mentioned, the above is a very simplistic way of estimating the backup needed. In order to not spend any more on battery backup than is actually needed, you also need to know the expected seasonal variance in output from your installed system and also any corresponding change in demand. Online tools like the project return estimator from EnerMark can help you estimate seasonal variation in output from your proposed system. As far as your own demand is concerned, you can always look at your electricity bill for various months and estimate.

  • Use the system to produce electricity for selling to the utility company or state electricity board and not store any electricity: In many states utility companies and electricity boards have announced net-metering policies. What that means is you can deduct electricity produced by the system by pumping it back to the grid. So for example, your system produces 200 units of electricity a month and your monthly consumption is 1000 units. Instead of storing the electricity with battery backup, you can sell the 200 units back to the grid and reduce your electricity bill to 1000-200 = 800 units. Also, in many cases the buyback rates that the state governments have announced (some times upwards of 8Rs/unit) are higher than the cost at which electricity is supplied to the customer. So, you can save even more on your electricity bill. In order to have your solar energy system work this way you need to install a grid-tied system and you can avoid the cost of battery backup. The down side, you don't have a way to use the energy from the system to handle power cuts.

Most likely, depending on your requirements the ideal configuration for you will lie somewhere in between these two extremes. A good installer should be able to provide estimates for various scenarios that fit your needs. So that you can compare before investing in the system.

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answered 2015-02-24 09:17:09 -0700

ramesh gravatar image

For direct Grid tied Solar Roof top systems you do not require batteries. Batteries are essential for stand alone solar P v systems in remote locations.

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