Welcome To Our Free Solar Panel Calculator And Solar Power Calculator Designated For Designing Off-Grid Solar Power Systems and On-Grid Solar Panel Systems.
If you want to design your off-grid solar power system for your off-grid home, cabin, cottage, or lodge and mobile solar power system for your RV, van, motorhome, car or boat or your grid-tied solar panel system for your residential home you’ve come to the right place.
Please scroll down to read the Help file showing you how to use this free solar calculator. To use our solar power calculator you need to have Adobe Flash Player installed. Therefore, If you are using iPhone/Android you may have difficulties in viewing our solar calculator.
For Chrome browsers: The calculator needs Flash to work
If the solar calculator isn’t working, you might need to change your settings to allow Flash. To the left of the web address, click Lock:
or Info ‘View site information’.
At the bottom, click Site Settings.
In the new tab, to the right of “Flash,” click the Down arrow and then Allow.
Go back to the site and reload the page.
Always click on the ‘Update’ button below the solar power calculator after entering new values in the calculator.
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Using the On-grid systems solar panel calculator for designing grid-tied solar power systems
Other useful solar power calculators:
- Solar battery calculator
- Solar panel output calculator
- Solar PWM charge controller calculator
- Solar DC Wire Sizing Calculator
Here is a quick guide on how to use the calculator.
Disclaimer: The provided calculator is for informational and educational purposes only. By using this calculator you acknowledge that we can’t be held responsible for any damages as a result of using this calculator
1. How many KiloWatts-Hours (kWh) do you use per month?
You are asked to quote your monthly consumption according to your monthly electricity bill.
2. What percentage of this power will be used by renewable solar energy?
If your home is connected to a utility grid, it is rather uncommon to offset all of your consumption to a solar electric system. A fair percentage is usually 30 to 40, you are free however to choose a lower or a higher percentage value.
3. Average Sun Hours per day?
You can find below information on how to find Average Sun Hours per day also known as Perfect Sun Hours/PSH/ for location in the USA, Europe, Australia, and New Zealand, and rest of the world:
3.1 You can take this value for the USA by clicking on the following link:
expand the ‘Solar Resources’ folder on the left and tick the ‘Avg. Annual Tilt at Lat’ checkbox. After that, you will see a map of the United States with Average Sun Hours plotted on. Then by clicking on the little black arrow right to the checkbox, you can expand the legend and see the value of Average Sun Hours for your location after zooming in the map as much as you need to find the place where you live.
Eventually, you get the minimum and the recommended size (in Watts) of the solar system you need. ‘System size’ means the total power of the solar panels that need to be installed on your roof to meet the electricity consumption target you want to offset to the solar system.
3.2 You can find the Average Sun Hours per day value for Europe by clicking on the following link:
http://re.jrc.ec.europa.eu/pvgis/countries/europe/EU-Glob_opta_publications.png
Please don’t forget to divide the value of the yearly sum of global irradiation in KWh/m2 by 365 to obtain the value for average Sun Hours per day.
3.3 For Australia and New Zealand:
solarpanelsvenue.com/out/australia_sunshine_hours.JPG
3.4 If you live outside the USA and Europe you can find the Average Sun Hours per day value for your country by using the World map of direct normal irradiance, which means that these values are applicable for the solar panel held perpendicular to the sun rays. In other words, the tilt of your solar panels is equal to the latitude of your place.
Please don’t forget to divide the value of the yearly sum of direct normal irradiance in KWh/m2/y by 365 to obtain the value for average Sun Hours per day for your location
On-Grid Solar Calculator Assumptions: Recommended System Size assumes 85% solar system efficiency or in other words 15% total system losses.
How to calculate the number of solar panels needed for your solar system?
The number of solar panels needed= Recommended System Size in Wats/Chosen Panel in Watts. Round up the calculated value
For example, you have calculated that you need a Recommended System Size of 5000Watts.
You have chosen your system voltage to be 12V and your solar panel to be 240Watt for the 12V solar system.
Then the number of solar panels that you need is:
The number of solar panels needed=5000/240=20.8 solar panels. After rounding it up we receive that you need to buy 21 solar panels.
Please, use the update button below the calculator body to update the calculated results if those results are not updating automatically.
Using the off-grid system solar panel calculator
1. What is the total Watts (W) you electronics will consume?
You need to sum the wattages of all the electrical devices you use on a daily basis and therefore you want your off-grid solar system to support. Each device has its wattage on its back label. So, please enter the sum of Watts your electronics consume daily.
2. For how long are you planning to run these devices?
You should decide for how long you have all these devices plugged in every day so that the solar system will be able to power them. Here you need to enter the average daily hours of operation rather than the maximum ones.
3. Charge Controller efficiency (PWM: 80%, MPPT: 92%)
The charge controller is a device that manages the battery of a solar system. PWM charge controllers are less expensive than MPPT charge controllers but they are also less efficient.
4. Average Sun Hours per day?
As it has been explained above for the off-grid solar system
Off-grid system calculator assumptions
1. Calculated battery size provides:
-up to 2 days of autonomous work with no additional charge of battery due to bad weather or system failure at 100% battery discharge, which is not recommended and may destroy your batteries.
-up to 1.65 days autonomous work with 80% battery discharge
-up to 1-day autonomous work with 50% battery discharge.
2. Minimum system size takes into account 3% cable losses and 80% efficiency of the battery bank. As you know batteries have losses due to temperature influence and discharge rate. Generally, lower temperatures, especially negative ones, and higher discharge rates in Amperes may drastically reduce the battery bank efficiency.
3. The Recommended system size takes into account the charge controller efficiency being inputted.
How to calculate the number of solar panels needed for your solar system?
The number of solar panels needed= Recommended System Size in Wats/Chosen Panel in Watts. Round up the calculated value
For example, you have calculated that you need a Recommended System Size of 5000Watts.
You have chosen your system voltage to be 12V and your solar panel to be 240Watt for the 12V solar system.
Then a number of solar panels that you need are:
The number of solar panels needed=5000/240=20.8 solar panels. After rounding it up we receive that you need to buy 21 solar panels.
Please, use the update button below the calculator body to update the calculated results if those results are not updating automatically.
Last but not lease you can discover how to design the over-current protection (the fuses, breakers and etc) in this easy to follow sizing guide.
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