The pros and cons of the PVWatts solar calculator

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The PVWatts solar calculator from NREL (National Renewable Energy Laboratories) is a great free, online solar calculator that consumers can use. However, it may or may not be the best solar panels calculator for homeowners to use depending on what exact information you are looking to calculate.

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Advantages of the PVWatts solar calculator over the Solar-Estimate.org solar calculator

The PVWatts solar calculator has two main advantages over the Solar-Estimate calculator and indeed any other solar calculator on the internet;

  • It allows you to accurately measure your likely solar production from your exact roof where the direction or tilt angle of your roof is not optimal. Essentially a perfect roof faces south and has a 27 degree pitch but many roofs are not like this. PVWatts allows you to enter the exact direction and pitch of your roof and adjusts solar production for this. Most other "solar panel calculators" (solar-calculators) simply assume production based on your location and assume a perfect roof.
  • It does not require you to enter in any of your personal details. The Solar-Estimate solar calculator requires you to enter personal information because this is the only condition under which solar companies will authorize the release of their system pricing data to users of the calculator.

Disadvantages of using the PVWatts solar calculator

PVWatts is an awesome solar production calculator but it is not good when it comes to giving consumers information about the costs and financial returns they can expect from installing solar panels on their homes. Specifically the PVWatts calculator:

  • Does not include incentive data in calculations making their results as to financial returns meaningless to consumers. The Solar-Estimate solar calculator has a;
  • Does not include market pricing data from installers in your area. Solar panel system cost changes from state to state depending on a number of local factors. With the the PVWatts solar calculator you need to know what the cost of your system will be, whereas the Solar-Estimate solar Calculator uses live pricing data received from more than 300 solar contractors that subscribe to our marketplace.
  • It requires you to know what size system you need. The Solar-Estimate calculator is able to calculate this once you enter your utility and average power bill because it has a database of average power costs from each utility in the country. It first reverse engineers this to get a monthly power usage and then applies your local weather data (that it actually gets from NREL) to work out what size solar system you need.

IN SHORT... If you are looking to do financial calculations use Solar-Estimate if you're looking to see the exact solar power production your roof will get compared to a perfect roof use PVWatts.

 

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