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Solar Design

 

Home TECH TOOLS LOAD CALCULATION

Designing and installing an appropriate solar electric system for your home or cottage generally requires some examination of your energy usage. Defining that usage allows you to size both your solar electric system and your battery storage needs. Follow the steps below to identify your unique energy requirements, and to define your solar energy system to fill those needs.

You can download this calculator in Excel (.xls) version here

Simple PV Calculator (AC loads only)
Step 1: Calculate AC load
AC Load (lights, appliances etc…) 
Rated Watts x
Hours per Day
x Days per Week =
Weekly Watt/Hours
Line 100
fridge
0
TV
0
Lights
0
Lights
0
TV/DVD
0
Microwave
0
Toaster
0
0
Line 105
Total AC Weekly Watt/Hours
0
Line 106
AC Inefficiency Factor:
1.25
Line 107
Total Adjusted AC Weekly Load (line 105 * line 106)
0
Step 2: Calculate PV System Requirements:
Line 202
Total Weekly Load (Line 107)
0
Line 203
Less Back-up Contribution from Utility/Generator that is not covered by the PV system
0%
Line 204
Total Weekly PV Load
0
Line 205
Daily PV System Requirements (Divide Line 304 by 7)
0
Line 206
DC System Voltage (12 / 24 / 48)
12
Line 207
Total Daily Amp/Hour Requirement (line 205 ÷ line 206)
0
Step 3: Calculate PV Array Size:
Line 300
Total Daily Amp/Hour Requirement (Line 207)
0
Line 301
Bright Sunshine Hours (from Table)
4.25
Line 302
Array Current Required in Amps (divide Line 300 by Line 301)
0
Line 303
Module Current in Amps (from Data Sheets)
Example: Sharp 130
7.5
Line 304
Number of Modules Required in Parallel (Line 302 divided by Line 303)
0
Line 305
DC System Voltage (same as Line 206)
12
Line 306
Nominal Module Voltage
12
Line 307
Number of Modules in Series
1
Line 309
Total Number of PV Modules Needed (line 304 * line 307)
0
Continue to Step 4 if you need to calculate battery bank size for off grid or back-up power needs.
Step 4: Calculate Battery Bank Size:
(Remember: For back-up power needs only include those loads that will need back-up.)
Line 400
Total Daily Amp/Hour Requirement (Line 207)
0
Line 401
Desired number or autonomous days (usually 3.5 for PV)
3.5
Line 402
Total Daily Amp/Hour Requirement for given autonomy
0
Line 403
Maximum Drawdown (typically 50% for lead acid batteries)
50%
Line 404
Required Battery Capacity in Amp/Hours
0
Line 405
Cold weather De-rating factor (for batteries stored outside in winter)
0%
Line 407
Single battery capacity in Amp/Hours (20 hr rate)
310
Line 408
Number of Batteries in Parallel (line 404 / line 407)
0
Line 409
DC System Voltage (Line 206)
12
Line 410
Single Rated Battery Voltage (per unit) 
6
Line 411
Number of Batteries in Series (line 409 / line 410)
2
Line 413
Total Number of Batteries (line 408 * line 411)
0
   

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