The price of setting up solar panels can range anything from few 100$ to 10,000$, depending on various factors.
The factors include your panel physical size(dependent on personal energy consumption), wattage of the battery storing the electricity(if off-grid), inverter cost, type of the panel, the brand of make, the durability and any certifications the solar panel might have.
Calculating the total amount of energy you use is quite simple than it seems. If a lamp rated 14W is turned on for 3 hours, it would consume a total of 14*3=42 Wh energy.
Summing up the total power consumed by each appliance(on an average) should give you a rough idea on how much would be the daily power usage.
The article how many solar panels do i need to power my home? can help you in finding the power usage, size and cost of the required solar panel.
Calculating the battery capacity required
Batteries are used when off-grid power supply is preferred. Battery capacity, charge stored is measured in Ah(Ampere hour). For the conversion of charge into energy(Wh) we multiply the Ah with voltage of the device.
A battery rated 20 Ah, 10 v can provide us with 200Wh energy. The lamp rated 14W in the previous section if connected to this battery would last for 200/14 h=14 h 17 min.
Calculating the solar panel capacity required to satisfy the needs
A 10W panel will give 10W (0.6A * 16.5V) for each hour under standard test conditions (1000 W/m sq and 25 deg C).
Choosing the type of panel based on roofing
The roofing of the house needs to be south facing for better exposure to solar rays. If you have limited roof space you should prefer mono-crystalline solar panels since it is efficient, on the bad side they are quite expensive .
If you have a good amount of roof space, you may consider between mono crystalline panels and poly crystalline panels, but poly crystalline panels are less efficient than mono crystalline panels. Hence there is a need to sacrifice money over efficiency. Better the efficiency, longer is the energy output.
Solar panels tend to work less efficiently, if the surface temperature rises. hence panels with lower temperature co-efficient rating should be preferred. Panels with positive tolerance tend to produce wattage in excess.
A panel with positive tolerance with 200W rating may produce 205W. The more efficient is our panel, the more is the light energy converted to electrical energy.
The efficiency of inverter do play a role in the total efficiency of the system. The efficiency of inverter can range from 95% to 97.5%. The more efficient the inverter, less will be the heat loss during the conversion of DC to AC.
Government based rebates
In order to promote the use of green energy,many countries have come up with rebates on setting up self-sufficient home, which should save good sum of money. The rebates are country dependent. The rebates such Feed-in tariff, renewable heat incentive are implemented in considerable number of countries.