It is usually mentioned with letter ‘W’ only. You most probably already know that Watt is a measuring unit of electric power which is a calculated by this formula. (Volt X Amp = Watt). You should know your energy requirement for instance If you need 300 Watts to power your house then you can buy three 100W panels or two 150W panels or even one big 300W panel.
Before you buy a solar panel, you must know what voltage you require from your solar panel. The most common house hold solar setups require 12V or 24V stable input from solar modules. Please note that to charge a 12V battery you will need 15V or even 16V volts in some cases. Also, solar panel volts fluctuate a lot due to inconsistent sunlight. Also when you put load on solar panels, their voltage will drop accordingly. therefore, for a 12V circuit, 16.5V to 22V solar panels are used. Similarly, for 24V circuits 31.5 to 44V panels are used. If above is too hard on your mind then remember a general rule, multiply your circuit voltage with 1.5 and find a solar panel around that value. For instance, if your circuit is 12V, multiply it with 1.5 (12x1.5=18V) and you will find 18V solar panel is suitable for your circuit.
Always check Amp rating of solar panel on information sticker before buying it. In fact, its better to take an Amp meter with you to check the actual output Amps of solar panels. To do so, you will have to go the market at a time when sunshine is at its peak.
Old solar cells have less life span as compared to modern solar cells. Make sure that the solar cell you are purchasing has at least 20 years of life.
Some modern solar panels are highly efficient which means they give more power while covering less area on your roof however cost more. You should probably only consider the more efficient solar panels if you have less area on your roof otherwise there is probably no need to pay more for same power you can get in lower price from standard solar panels.
Cost to Energy Ratio:
Although some solar panels list “Cost to Energy Ratio” on their information sticker but I recommend that you should calculate it by yourself. Take a multimeter with you and go to the market. To check cost to energy ratio of a solar panel put it in sunlight, take reading of volts and amps and then multiply both numbers. This will give you actual watts of the solar panel now divide it with solar panel’s price. For example, if solar panel is 150W and costs you $100 then 150/100 gives you 1.5. This means you are getting 1.5 Watts for every $ you pay.
Alternatively, if you don’t have a multi-meter then you have no choice but to believe the Watts written on solar panel and divide them with its price to calculate how much watts you are getting per $. This will help you in short listing the vendor.
Solar panel is a fragile item so always check physical condition of solar panels to see any cracks or lose frame. Also make sure the fitting holes on the frame match your fitting stand.
Posted or Updated On:May 31, 2019