AND Search OR Search
Phrase Search Show results per page

System Sizing for solar

PV - How many panels do you need?

a) Calculate your daily average sun hours for the year. These figures are available from insolation maps(not insulation)


Geographical areas are divided into insolation zones that show the average number of hours of daily full sun hours available in your area.

b) Take the total daily ac-dc loads calculated in watt hours(from your total load work sheet) and divide by your daily full sun hours.(above)

c) The total is the amount of watts that you need to generate from your system for each hour of full sun.

d) Take the total amperage available from your pv panel. ie say for example a panel that you have puts out 8 amps in full sun.

e) Take the total panel output and multiply times your battery voltage.

f) Your true power is = amperage x charging voltage.

g) Divide line c by line d to get the total amount of panels that you need for your system. Round up the total. Winter months will give you a lower daily sun average so be sure to allow for this in your calculations.

Battery sizing - series - parallel

a) Enter daily amp hours ( from your ac-dc loads work sheet)

b) Enter number of days of storage capacity ( average 5 days)

c) Multiply line a by line b to get the amount of amp hour storage needed.

d) Enter the batteries discharge limit. ( between 0.2 - 0.8 ) deep-cycle lead acid batteries should not be discharged more than 50%. or a discharge limit of 0.5

e) Divide line c by line d.

f) Select the closest multiplier below for the average ambient winter temperature your batteries will experience. enter the multiplier here.

80 f/26.7 c......1.00 multiplier

70 f/21.2 c......1.04 multiplier

60 f/15.6 c......1.11 multiplier

50 f/10.0 c......1.19 multiplier

40 f/4.4 c.......1.30 multiplier

30 f/-1.1 c......1.40 multiplier

20 f/ 6.7 c......1.59 multiplier

g) Multiply line e by line f.

This ensures that the battery bank can endure cold temperatures.

This is the total battery capacity required.

h) Enter the amp hour rating for your batteries.

i) Divide line g by line h. Round off to the next highest number.

This is the number of batteries wired in parallel required.

j) Divide system voltage ( typically 12, 24 or 48 ) by battery voltage.

This is the number of batteries wired in series required.

k). Multiply line i by line j.

This is the total number of batteries needed.

Calculate your solar module requirements.

Solar panel array sizing sheet

l) Total of amp hours per day (load sizing work sheet )

m) Multiply line l by 1.2 to account for battery loss

n) Average sun hours per day ( from solar insolation chart )

o) Divide line m by line n for total array amps required

p) Peak amps produced by the solar array

You can determine peak amperage if you divide the array's wattage by the peak power point voltage, usually (17 to 17.5)

q) Divide line o by line p and round up to highest whole number.

r) This equals the total number of panels required if wired in parallel and determines the number of panels in each series set required to supply the needed dc battery voltage.

Multiply line q by line r.

This is the total number of solar panels required.

Calculate your proper PV tilt angle