America's oldest and best known online solar calculator celebrated a milestone this week when the 100,000th consumer used the free online solar calculator to evaluate solar panels as an investment.

The solar calculator on http://www.solar-estimate.org is a legend of the American solar industry.

It was originally developed with funding from the US Department of Energy and was purchased by Solar Investments in February 2013.

This solar power calculator allows a consumer to enter in the details of their zipcode, their utility and the size of their monthly electricity bill to find out the following:

What size solar power system they need to cover their utility bill;

How much power will be produced by this size of solar power system annually;

How many square feet of roof space the consumer needs to fit such a system;

How much a solar power system of this size is likely to cost (based on industry average pricing data collected from over 200 installers across the country); and

The consumers return from installing a solar power system on their house and their payback period in years.

The Solar Estimate solar calculator incorporates production data known as PV Watts (supplied by the good folks at NREL) but extends this with data about the cost of solar and also solar incentives.

This makes it a great one stop shop for consumers that are considering installing a solar power system at their house