Frequently Asked Questions
Who are the calculator’s primary intended users?
This calculator has two primary end users: 1) solar advocates or policy makers that can leverage this calculator to quickly quantify the residential solar economic impacts of different solar policies (e.g., net metering changes, incentive changes, and financing terms), and 2) homeowners looking to accurately estimate the economic and climate benefit of installing rooftop solar and compare proposals on an apples-to-apples basis.
What are this calculator’s advantages over other free residential solar calculators (e.g., EnergySage’s Solar Calculator and Google’s Project Sunroof)?
This calculator’s primary advantage is that it enables users to quantify residential rooftop solar’s economic and climate impact more accurately and dynamically in a user-friendly interface. It enables users to modify all key input values for solar advocates to compare different solar policy changes and homeowners to compare different solar quotes, including the impact of battery storage.
Why does this calculator show different results from my solar installer proposal?
Since many residential solar installers use different assumptions and models when estimating a project’s economic impact, it can be helpful to ask each installer for their assumptions in key categories (e.g., electricity rates and usage, solar PV system design and generation, upfront costs and financing, and incentives) and use this calculator for an apples-to-apples comparison. Consider using the “Get Shareable Link” function under the results table to share your analysis with your installer to resolve any discrepancies.
How can I share my results with others?
You can click on the “Get Shareable Link” link below the results table to send your scenario and results to others or bookmark it to refer back to.
Where can I find the sources for the default data inputs?
You can click on the “Download Excel-Based Calculator” link below the results table to find all sources at the top of their respective tabs in that file.
How often is this calculator updated?
This calculator is typically updated near the end of each calendar year with the most recent state-specific average residential electricity rates, net metering rates, and average solar and battery storage upfront costs and incentives.
How does this calculator estimate the economic impact of battery storage?
When the hourly solar electricity generated is more than the home’s hourly load, the excess solar generation is used to charge the battery up to the battery’s full capacity. When the hourly solar electricity generated is zero or less than the home’s hourly load, the battery discharges stored energy to power the home at its rated hourly capacity. For more information, select “Download Excel-Based Calculator” under the Emissions Impact results and review the “Solar (+ Storage) Production” tab.
Can I incorporate a time-of-use electricity rate that into this calculator?
This calculator uses fixed charges ($/month) and variable electricity rates ($/kWh) but does yet have the ability to factor in time-of-use rates. You could consider using your utility’s general residential service, non time-of-use rate as a proxy.
How can I correct a default value that is outdated or incorrect for my state?
You can manually change all data inputs by overriding the default value. If you see a default value that you think is outdated or incorrect, please contact Ryan Shea at rshea@rmi.org.
Who can I reach out to with additional questions?
Please contact Ryan Shea at rshea@rmi.org with all comments or questions.
