Solar Panel Sizing


* PHOTOVOLTAIC (PV) means LIGHT converted into ELECTRICITY. PV Solar Panels require LIGHT to generate electrical power - NOT HEAT (solar panels work better when kept cool). Power generated during the day is normally stored in a battery for 24 hr usage. This makes Solar Panels ideal for Boats & Motorhomes where mains power is limited.

* “What size Solar Panel do I need to keep my batteries charged?” Depends on how much you are drawing from your batteries each day. You can calculate your total usage by the Amp rating of each light / TV / water pump / fridge by the number of hours in use each day. This will give you Ah per day. If your panel and batteries are sized correctly, you could have a system that is totally self-sufficient for your needs. 

“What power output can I expect from a particular size Solar Panel?”  Each panel is usually rated in Peak Watts (Wp) and Peak Amps (Ip). This figure is with bright sunshine at 90º to the panel. Due to changes in the sun’s position during the day this output will be reduced. As a UK guide only we would say take the number of daylight hours (i.e. 6 hrs in March / 15 Hrs in July) multiplied by HALF the rated Ip, e.g. 2.35 Amps (40 Watt Panel) in Summer will give 15hrs x 1.175Amps = 17.6 Ah per day approx. This is a guide only as cloud & panel position will affect actual output.

“What else do I need to operate a Solar Panel?” As some panels are capable of putting out in excess of 12V a VOLTAGE REGULATOR will be needed to limit the charging into your battery. If left unchecked it could damage your battery by over-charging it. These can be as simple or as sophisticated as you want.


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