Solar education website SolarPowerRocks.com has announced plans to add a new tool from Solar-Estimate.org that accurately calculates the cost of residential solar panels.

While Solar Power Rocks has long offered helpful resources for energy consumers and those interested in going solar, they have been reluctant to add a solar cost calculator. Many solar customers are interested in seeing just how much they’ll save by switching to solar energy, but some free solar calculators make broad generalizations to provide widespread support for American energy consumers. Now, a new tool from Solar-Estimate.org has made a solar calculator that’s more than 90% accurate, prompting Solar Power Rocks to add the calculator to its site and make it widely available to the thousands of people that visit its site each month.

In order to show customers the financial impacts of switching to solar, the new, no-cost calculator considers a variety of factors, including a user’s zip code, local utility rates, time-of-use electricity billing, climate conditions and all available incentives, like the solar Investment Tax Credit.

Solar energy production data from the National Renewable Energy Laboratories (NREL) enables the calculator to accurately estimate how much electricity a solar panel will produce in a given location. However, this data only represents a portion of the information necessary to create an accurate solar estimate. It’s also important to take into consideration details related to a consumer’s rate plan and the rate modeling structure that the local utility uses. Solar-Estimate.org’s calculator goes a step further by incorporating Genability’s extensive utility rate database that includes tens of thousands of different rate plans and electric usage profile modeling.

A residential usage profile is a representation of how a homeowner is likely to consume electricity over the course of the year, as well as throughout the day. Genability can generate and tailor these profiles to the local climate of a consumer based on location information. For example, if a consumer lives in a region with a hotter climate, most profiles will assume that during the summer there will be an increase in electricity usage because of air conditioning use and that less electricity will be used at night. The usage profiles can also be adjusted to simulate actual energy usage by entering information about a recent electric bill.

Because the calculator can model the details of a specific electricity rate plan, it can also estimate how much electricity is consumed on an hourly basis. Some utilities offer what is typically referred to as a “time-of-use” rate. These rates are structured in such a way so that energy consumers are billed according to the time of day electricity is used. Solar-Estimate.org’s calculator uses local rate plans and usage profiles, enabling the calculator to also give time-of-use customers an accurate solar estimate.

Solar-Estimate.org’s new solar calculator represents a boost in accuracy for anyone looking to get a free solar estimate. Solar Power Rocks’ announcement to add the calculator represents the second website to do so, in addition to SolarReviews.com.