One of the most important aspects of designing a solar array is sizing module strings to operate within the parameters of the selected inverter. Renewable Energy Associates has developed a tool to help in that process. Most inverter manufacturers offer some type of sizing tool, whether it’s simple or advanced, it’s usually limited to selecting only their products. The REA System Sizing Tool lets you select from a wide variety of products and manufacturer’s. Our tool is free and available for download through the link below.
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Have a question about the string sizing tool or a suggestion which might make it better? Feel free to leave a comment below. Updates will be made monthly.






Updated v7.4.4
MAGE Solar
-245W
-250W
Great tool. Can you add Mage 250w to the list? Thanks
Updated version 7.4.3
Added
- Global Solar PowerFLEX BIPV 250/275/300W
Updated version 7.4.2
Solarworld poly modules TC values updated
Solarworld 245 & 250 mono black modules added
Solarworld module Rated Power Tolerances updated
SolarWorld module Vmp coefficients need to be corrected to match the latest data sheet values for 220 poly, 225 poly, 230 poly, 235 poly, 240 poly and 245 poly modules. 245 mono black and 250 mono black modules could be added. Also all module Rated Power Tolerances are -0/+5Wp.
Thanks for the update!
Updated version 7.4.1
- Schuco MS 08 series added
- REC PE series electrical specifications updated
Updated version 7.4
Aurora Power One Inverters
- Fixed the minimum MPPT value.
Note: At this time our tool is unable to simulate multiple MPPT configurations.
Updated version 7.3.1
Solarworld TC values updated
SolarWorld module data needs to be updated. Minimally TC values do not reflect those reported within the latest data sheets available on the SolarWorld website.
Updated version 7.3
SunPower Modules
- SPR-320E-WHT-D
- SPR-327NE-WHT-D
Updated version 7.2
Silicon Energy inverters
- SiE3840
- SiE5300
REFUsol inverters
- 012K-UL
- 016K-UL
- 020K-UL
- 024K-UL
itek energy modules
- IT 225-255W
Please add REFUsol string inverter line to the tool. Unfortunately they don’t have a string sizing tool available. Nice product though.
Please add module SOLAR SLW0005 SIZE 63.9 X 32.0 X 1.6 INCH, 40LB, ELECTRICAL RATING 120WP 35VMP 4.72IMP, AMPERAGE 4.72 VMP 5.4 ISC.
And Xantrex TR1512-230-50 inverter module.
Thanks,
What is the manufacturer of the module you are requesting? Could you send us a spec sheet? The Xantrex inverter is a charge controller and battery based inverter and unfortunately our string sizing tool is not set up for battery based PV systems.
Updated version 7.1
-Fixed Enphase voltage drop calculator
Updated version 7
- Added and updated hundreds of modules and inverters. To many to list.
- Formatted for easy printing.
Note: We do our best to make sure there are no errors with the tool but if you find one please notify us right away so we can fix it. Thanks!
John
Can you add ET Solar Modules M572185,190 & 195 and P660235 – 250?
I didnt really make sure to see if you have the Conext TX Series Inverters 2800,3300,3800,and 5000?
The latest update includes the ET modules you requested and the Context Inverters can be found under Schneider Electric.
Updated v6.9.1
KACO new energy, Inc. inverters:
- 6400xi
- 7600xi
Hi,
Can you add the KACO 6400xi and the 7600xi to the tool?
It’s a nice calculator!
Cheers,
Paul
Is there a way to add inverters to the spread sheet? I’m trying to add a Xantrex XW6048 but can not modify the worksheet. This is a neat tool you created though. Thanks.
kenny
We do not have a way for users to add equipment but you can make a request for equipment to be added. Unfortunately the Xantrex XW series inverters do not work with our string sizer because they are battery based inverters.
Updated as of 10/11/11
v.6.9
Added:
-Lumos module series
-SolTech module series
Fixed:
-Two word state (New Jersey, New York, New Mexico ect.) drop down location list.
Changed:
-Voltage drop calculations to be based off of 12AWG or larger wire.
Can you add the 250-watt 1SolTech STH-250 panel, please?
Great tool – thanks for the effort!
Hi Jon,
Can you add Lumos 180 LSX black to the lineup?
Thanks
Shawn
Updated as of 9/28/11
v.6.8
Added Solarworld SW 255 – Mono
Please add Solarworld SW 255W Mono Modules
Updated as of 9/19/11
v.6.7
Added Enphase Internal Voltage Drop Calculator
Updated as of 9/7/11
Fixed source circuit voltage drop calculator
The version I downloaded tonight did not have the source circuit voltage drop calc fixed.
Fixed now. Thanks for letting me know.
Thanks for your help. It is possible in tap “string size” add Puerto Rico in State area. In this tap also in “array design options” area, what you can do for more than one inverter or multiple inverters?
From what I can tell there is no ASHRAE data for Puerto Rico but if you find any data I can get it into the tool. If you are looking to size a PV string located somewhere outside the united states the manual temperature input area is your only option. At this time the REA string sizing tool has no option for multiple inverters.
Updated as of 8/3/11
-Minor text changes
Added:
- Sanyo 225A
- Kyocera KD 200-60 series
It is possible to add Kyocera KD 200-60 series (230,235,240,245 watts) solar panels?
Thanks
Please add the Sanyo HIT Power 225A module to the stringing tool.
Thank you very much – this is a great tool!
Updated as of 7/12/11
Fixed:
- Voltage drop calculations
Added:
- Solarworld 240 & 245 poly modules
Updated as of 6/23/11
Changed:
- Temperature correction is based off of ASHRAE values
- Voltage drop calculator has an additional AC section
Added:
- Sunpower 320′s
- Westinghouse (Andalay) WHS_FL175
- Canadian Solar CS6P-M & CS6P-P Series
- Suntech 205
- AUO Optronics Corp PM Series
- Fronius CL Series
- Nexus Energy DJ Series
- UniSolar PVL144
- Enphase 215
Is it possible to update the “System Sizing Tool” with the new Enphase 215 microinverter as well as the Uni-Solar PVL144′s?
Thank you,
Dan
There are no strings when using microinverters since each module is inverted individually.
We have added Enphase inverters to this tool more as a convenience then anything else. Like you point out, there is no string sizing involved with micro inverters which is why when you select an Enphase inverter and a Enphase inverter compatible module you only have the option of selecting one module per inverter. If there is a discrepancy somewhere in the tool it is likely because the module selected is not compatible with Enphase inverters. Please check the Enphase site for the module compatibility list. A future string sizing tool revision might include this compatibility list. Using the voltage drop calculator to calculate voltage drop with Enphase inverters is the main reason why Enphase inverters were included in this tool. Thanks.