How to optimize off Grid solar System ?

Take inverter efficiency , according to "Essen Solar Off Grid Inverter" or "Sun grow inverter"

Solution :

First of all solve This problem according to Question given data

Step 1 = Power = 840 Watt
 Total Wattage = 2900 Wh

According to safety Factor =

Watt = 840 * 1.25 = 1050 = 1000 W
Wh = 2900 * 1.25 = 3625 Wh

Step 2 : Size of Battery

Output energy of battery = 3625 / 0.90 =  4028 Wh   let us take DoD = 90%

Ah =  4028 / 0.90 =  4476 Wh

Since system is 1000 W , so it is not compatible to take 12 V battery, For this 24 V is taken

A h = 186 Ah

Step 3 : Calculate detail about module, for 250 Wp , because it is given or demanded by customer.

Total panel wattage needed =  Battery output / Efficiency =  4740 Wh
Total solar radiation in Delhi , Nirman Vihaar in winter = 4740/4.4 =  1077 Watt . =   1 kw

Peak Sunshine hour in winter =  Dec - March
Summer Season Month =  June to Sept


For 250 Wp
  total number of module = 1000/250  = 4

For 250 Wp 

Open Circuit Voltage (Voc) in Volts  37.20  

Short Circuit Current (Isc) in Amps  8.96  

Voltage at Maximum Power (Vmp) in Volts  30.80 

 Current at Maximum Power (Imp) in Amps  8.12 

For further calculation  type of connection we need inverter specification :

Capacity = 1000 Va

Battery System = 24 V

Battery Support = 80 Ah - 200 Ah

Panel Support = 1000 Wp

Solar Panel Current = 40 amp

Solar Voc = 30 V - 85 V

This specification is taken from Micro tech solar inverter with MPPT 1 KW
No of Series connection is possible = 2 , 74.4 <85 V acceptable
No of parallel connection is possible  = 2, 16.24 < 40 amp  acceptable

but power = 1000 Wp, Which is also acceptable P =Vm *Im

So all connection would in parallel

P = (30.80) * (8.12 *4), = 1000 Watt  Which is acceptable by inverter

costing = 11550 * 4= RS 46200

It should be noted Every consultant and designer should avoid parallel connection as much possible low because of heat or current losses.

Imp Note : For a solar Consultant Along with Battery sizing, cost optimizing is also very important factor. Cost optimizing is not about first time design. you have to design with different components rating for same system capacity .

Here let us start to optimize system :

Clearly we can see different rating of module with per watt cost. We should opt for low wattage cost i.e. Rs 43


we have to module regarding Rs 43 watt .
Let us look one by one

We have checked earlier for 250 Wp ,Both will be little more  in Watt and in Cost by Panel 250 Wp
For 330 WP

Total number of Module =  3
Possible series connection =  1  , 45.80 <85 V, acceptable by inverter
Possible parallel connection = 27.39 <40 amp ,  acceptable

Power = 36.70 * (27.39) =  1005 Watt. This is perfect.


above condition are not companionable for inverter

Cost = 14500 *3 = Rs 43500 = 43 per watt

Cost of inverter  1 K w = 14500   14.5 per watt

Now , Its time to select battery ,

 we have lot of option
1. 24 v / 200 Ah = 1 battery
3. 12 v / 100 A h = 4 battery , series and parallel
4. 12 v 50 Ah = 8 battery etc

Just need to calculate cost from supplier of internet or other sources :

24 v / 200 Ah = 1 * 9500 =  Rs 9500
12 v / 100 A h = 4 * 7450 = Rs 29800
12 v 50 Ah = 8 * 5410 =  Rs 43296

Clearly we should opt 24 V / 200 Ah  single battery

other miscellaneous charge included = 15000 k max.
you can also optimize in wire ...


330 Wp panel
24 v / 200 Ah battery
1 KW inverter

Total cost charge = Rs 43500 + 14500 + 9500 + 15000
                               Rs 82500
Total per watt cost should not high from 75 - 80 per watt

A 1 kW off-grid solar system will cost you around INR 95,000 if you buy it from Loom Solar
according to loom solar

This is whole process of cost optimizing

This whole optimizing will be done in OFF Grid Software in Sunday Webinar after Solar Pump

Tilt angle in winter = 28 + 15 = 43 degree


BY help of Above system, you can fully charge your battery in 4800/800 = 6 days.

For charging battery per day , you have to increase Size of Inverter and Solar panel in such as way, Battery will receive 4800 Wh = 1100 watt per day.