Firstly, it is very necessary to know what gadgets you will be using (eg.tv, decoders, refrigerator, fans et al) and how long you will use ( how long you desire the system to power these gadgets in the case of utility power outage ) and how much energy your battery can store and which solar panel (rating in power) will supply the required energy.
A lot goes into calculating the cost of setting up a solar system. First one has to determine the energy required by your gadgets.
The power consumption of appliances is given in Watts. To calculate the energy you will use over time, just multiply the power consumption by the hours of use.
Eg. If I have
55 Watts LED TV set which I desire to use for 6hrs,
25 Watts Decoder for the same period, and a…
50 Watts Stand Fan which I want to use for 3 hours…
….. Thus the energy required by these gadgets for the desired period of usage is calculated as….
the energy for each appliance is Watts x time (hours) = Wh
So, the watt hours for the TV = 55 x 6 = 330 Wh (watt hours)
For decoder = 25 x 6 = 150 Wh
For Stand Fan = 50 x 3 = 150 Wh
Add the watt hours for the individual appliances ie. 330 + 150 + 150 = 630 Wh (watt hours)
This means that the system required will be that which has the capacity to generate and also the capacity to store energy in excess of 630 Wh daily. Here it gets tricky, consult a professional photovoltaic system designer to size an appropriate system for you because a lot of variables such as location, changing weather conditions, system losses due to component inefficiencies et al comes into the equation.
Now, storage for the generated energy? Solar panels output is assessed by the cumulative energy generated during the day. Output at any point in time during the day is constantly changing with the changing weather conditions. Thus a storage (batteries) with the capacity to store energy generated is mandatory. Using our example above, the required Storage would be not less than 630 x 1.5 = 945 Wh ( i.e. 80 Ah )
The last but not the final cost determinant is inverter. This is the powerhouse of the system, it converts the DC energy generated by the panels or stored in the batteries to AC energy that is required by your home appliances. The size and capacity is determined by the size and energy required by the load you intend to use it for.
Thus in summary costing is function of:
1. Solar panels – quantity & class/grade/efficiency
2. Charger controller – capacity/efficiency
3. Batteries – capacity/type/grade
4. Inverter – capacity/type/grade
5. Others – cables, Breakers, surge protectors, racks, mounts, service fee et al.