Yes, that's true, due to high cost of Deep-Cycle Batteries and Solar Batteries in Pakistani market, solar energy will cost you more than WAPDA (the Main or Utility provider in Pakistan).
Assume you have installed 500-Watt Solar System with back-up time (14-hour in case of stand-alone solar system and 3.5 hour in case of hybrid solar system) and your inverter's efficiency is above 85 percent.
Stand-Alone Solar System: 500-Watt for 24-Hour (14-Hour backup time + 10 Sunny Hours)
For 500-Watt stand-alone solar system you need minimum 800-Amp Battery Bank (Eight Batteries of 100-Amp each) and to charge this battery bank and to supply power to connected load in day, if sun is available for 10-hour (assuming 7-AM to 5-PM for summer in Pakistan), you need minimum 1000-Watt A-Graded solar panel bank. Enjoy power holidays in cloudy weather!
Hybrid Solar System: 500-Watts continuously run for 24-Hours
To run the same load with Hybrid Solar Inverter, 200-Amp Battery bank (two batteries of 100-Amp each) is must and to charge the battery bank and to provide the power the connected AC load at same time, minimum 900-Watt solar panel bank is needed. 200-Amp battery will provide 3.5 hours of maximum back-up time in case of load shedding. Charging of Battery with generator or WAPDA in cloudy weather.
Long backup time needs more batteries
Now just calculate the cost of Batteries in both cases. 100-Amp deep cycle dry battery will cost you Rs. 18,000/- approximately. If your system is designed and installed by qualified professionals your battery bank may lasts for more than four years. For stand alone system only the battery bank will cost you more than Rs. 120 per day based on four-year time period. (including cloudy days and short sun time in winters).
Initial solar system, installation or maintenance cost is not included in above calculation.
For hybrid system the cost you save from batteries will be payable to WAPDA for charging the batteries, in load-shedding, in night or in absence of Sun (cloudy weather) .
On the other hand, one unit of WAPDA's costs you Rs. 9 (with subsidy including taxes). To run the same load (500-watts continuously run for 24-hours) on WAPDA for 24-hours will cost you Rs. 108 per day.
Rs. 12 difference per day.
The ways to save your WAPDA electricity bill by utilizing solar energy system
There are the ways to save you electricity bill cost by properly harvesting solar energy. The two most cost effective methods are mentioned below:
Use 12-Volts DC System:
Everything is DC operated, DC Battery, DC Solar Panel, Solar Charge Controller and DC Load including DC Fans, DC Lights. No inversion / conversion losses.
A full sized DC Ceiling Fan is of 30-Watt.
100-Amp battery and 300-Watt panel is sufficient to handle 100-watt DC load for whole day. Cost you Rs. 12 per day.
Hybrid Solar Inverter with minimum Battery Bank and Maximum Solar Panels:
Use small battery bank only to utilize the solar energy in sunny hours, use inverter as normal UPS in night. This is the ideal use of hybrid inverter, low in cost and highly cost effective.
155-Amp battery is enough for this system. 500-watt AC load requires 50-AMP DC current to run via inverter, so 600-Watt solar panel will best in this situation.
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Read: Battery Maintenance Guide
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These results are based upon my personal experience, calculations and experiments. These results and calculations may be wrong because various assumptions are assumed while calculations, cause of writing this article is just to guide you in investing wisely.
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Also Read: How UPS works ?
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Year 2024 Update:
Note: This article was published in 2016, when WAPDA's provided electricity was not too costly, but now in June 2024, WAPDA's provided electricity is too highly charged or over costed, now in this time, the independent solar systems are more reliable and more efficient but initial cost is high. Independent Solar Systems are small systems consisting of Panels, Battery and DC Loads, I will write a complete article about it soon, meanwhile you can read about MPPT solar charge controller for independent solar system. On-Grid and Hybrid Systems are also dependent on WAPDA.
About Me:
I am an Electrical Engineer, recently got my degree and my final year project was also based upon Solar Hybrid Inverter. link to the research article published by me and fellow project group members. Comments, suggestions and corrections are most welcome.
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