Solar Panels

Assuming you are:

• Mumbai India
• 5 hours of TV+Set top box+Fan
• 2 days of "no sun operation"
• 50% maximum battery bank discharge (for longer life)
• Assume flooded cell batteries

A quick set of calculations would look like:

• (35 watts TV + 10 Watts set top box + 50 Watt fan) * 5 hours a day (or evening) = 475 Watt hours per day
• 475 WH per day * 1/0.85 AC inverter eff * 2 days of storage * 1/0.50 max battery discharge * 1/12 volt battery bank = 186 AH @ 12 volt battery bank

In North America, we would use 2x 6 volt @ ~200 AH batteries (golf cart batteries flooded cell lead acid) for a 12 volt @ 200 AH battery bank.

For sizing the solar array, we do two calculations. The first based on the size of the battery bank (larger battery bank needs more charging current). The second based on your daily load and hours of sun per day.

For charging, suggest 5% for emergency/weekend sunny seasonal power, 10%-13%-20% for daily year round loads of charging current. An example of 10% rate of charge:

• 200 AH * 14.5 volts charging * 1/0.77 solar panel+controller deratings * 0.10 rate of charge = 377 Watt array nominal (10% rate of charge)

And then there is sizing the array based on your loads and hours of sun per day... Assuming fixed array facing south for Mumbai India:
http://www.solarelectricityhandbook.com/solar-irradiance.html

Mumbai
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 71° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
6.54	7.17	7.42	7.14	6.69	5.63
Jul	Aug	Sep	Oct	Nov	Dec
4.94	4.85	5.69	6.29	6.46	5.98

Good amounts of sun... The least amount of sun you get is August at 4.85 hours of sun average (long term daily average for August):

• 475 Watt*Hours per day load * 1/0.52 off grid solar AC system efficiency * 1/4.85 hours of sun per day (Aug) = 188 Watt array minimum

Normally, you don't plan on using 100% of your predicted harvest... You have to decide on what is a daily "base load" (loads you want to run every day) vs optional loads (washing machine, vacuum cleaner, etc.)... Let's say that you want to run these loads every day (keep kids busy while you work around/at home). I would suggest that you plan on using 50% to 65% of daily harvest:

• 188 Watt "break even August" array * 1/0.50 base load factor = 376 Watt array suggested for loads and sun

Which happens to work out to be about 10% rate of charge array at 377 Watt array... So, for a 200 AH @ 12 volt battery bank a 377 Watt array (with a 200-300 Watt AC inverter) and a ~25 amp Solar charge controller would be a nice fit.

Details matter--The above sizes the battery bank and solar array... You need to decide if the assumptions here are correct for your needs. And then you need to look at hardware. What batteries are actually available (good price/availability), what size solar panels (a single ~377 Watt panel, or 3x 120 Watt panels, etc.) and what solar charge controller type (MPPT or PWM) will work.

You should do several paper designs and see what combination of panels+charge controllers make sense (377 Watt panel is "cheap" but MPPT controllers are expensive; 3x 120 Watt panels are more expensive, but PWM charge controllers are cheaper).

Anyway--Just a quick run at the assumptions you need to make and the math to figure out the supporting hardware. The battery bank is the "heart" of your system. And the solar array (plus how you run your loads) can make your battery bank "happy" or "murder it". 

-Bill