Solar Irradiance Calculator

This solar irradiance calculator shows you how much power you get from the sun at your location on an average day for every month of the year.

Solar irradiance is a measure of the suns power. Irradiance levels vary considerably at different times of the year, depending on the seasons, the weather and the time of day.

Our Irradiance calculator provides monthly figures showing the average kWh per square metre per day of energy that the sun provides.

How to use the Solar Irradiance Calculator

• Select your country from the list
• If you have selected the United States or Canada, please select your state or province/territory.
• Select the town or city nearest where you live.
• The solar irradiance calculator will then show monthly figures showing the suns energy as an average kWh per square meters per day, for your location.

How you can use the solar irradiance calculator information

The information from the solar irradiance calculator can be used to calculate the amount of power you can get from different forms of solar energy systems:

• To calculate the amount of solar energy you will get from a photovoltaic solar panel for an average day in any given month, for example, multiply the stated wattage of the solar panel by 75% (to account for inefficiencies in the power generation and capture) and then multiply it by the kWh/day figure for the month in question.
• stated wattage of panel x 75% x monthly insolation figure = average daily power

Irradiance Calculator Example: if you have an 80 watt solar power, and your monthly insolation figure is 4.0, you multiply 80 watts by 75% to give you 60 watts and then multiply this by 4.0 to equate to 240 W/h/day of solar energy.

• To calculate the increase in water temperature you will get from a solar hot water collector for an average day in any given month, multiply the size of the panel in cubic metres by the efficiency of the panel (typically 40-50% for a home made panel, 60-75% for a commercial panel), multiply this by the kWh/day figure for the month in question and then multiply this by 860 divided by the total number of litres of water you are planning to heat.
• size of panel in m² x panel efficiency % x monthly insolation figure x ( 860 ÷ number of litres of water ) = increased water temperature °C.

Irradiance Calculator Example: If you have a two cubic metre solar water heater that is 75% efficient and your monthly insolation figure is 4.0, your solar hot water system is producing 6kW/h/day of hot water. If you are heating up 200 litres of water, you can increase the temperature of the water by 25.8°C above the ambient water temperature.

Solar calculators

This calculator has been provide by The Solar Electricity Handbook. The website also includes other tools, including a free angle calculator and project analysis. If you are planning a project these are great tools and will assist you with the full planning process.

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A simple, practical guide to using electric solar panels and designing and installing photovoltaic PV systems.

The Solar Electricity Handbook assumes no previous knowledge of solar power systems, it explains how panels work, how they can be used and explains the steps you need to take to successfully design and install a electric photovoltaic system from scratch.

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