Google’s Project Sunroof

Curious to know what an investment in solar looks like?

Google’s Project Sunroof – an online solar estimator – can give you an estimate of the cost to install a system and years until payback. Estimates provided by Google’s Project Sunroof are based on current electric prices and compensation structures. Future changes in prices, credit amounts or billing structure will impact the estimated net savings and payback. Project Sunroof is not functional for all of Idaho Power’s service area, so we’ve provided three Project Sunroof examples of a typical home below.

Note: On Dec. 20, 2019, the Idaho Public Utilities Commission (IPUC) issued Order 34509 in case IPC-E-18-15, which reminds customers that Idaho Power’s on-site generation tariffs (Schedules 6, 8, and 84), as with all tariffs, are not contracts and are subject to change at any time upon order of the IPUC. Changes to the on-site generation tariffs in the future may include, but are not limited to, modifications to rates, billing components, billing structure, compensation structure, and the value for excess energy produced by the customer’s on-site generation system (and thus, the amount a customer would be compensated). Learn more about this case and order on the IPUC website.

The IPUC’s order is consistent with the Idaho Residential Energy System Disclosure Act, which requires solar retailers to provide a disclosure reminding potential customers that legislative or regulatory actions can affect or eliminate one’s ability to sell or get credit for any excess power generated by the system and may affect the price or value of that power.

Examples for using solar on-site generation to match nearly 100% of a home’s energy use
illustration of a small houseThe Jones’ House illustration of a medium sized houseThe Zhang’s House illustration of a large sized houseThe Jackson’s House
Average monthly electric use: 500 kWh 1,000 kWh 2,000 kWh
Average monthly bill:  $50  $100  $210
Solar system size needed: 4.3 kW  9 kW  18 kW
Purchasing with a loan
 Estimated 20-year loan cost $20,700 $38,800 $73,000
 Estimated break even point:  Beyond 20 years Beyond 20 years Beyond 20 years
Total savings after 20 years (Simple Savings)1:  -$6,000 (loss)  -$9,100 (loss)  -$13,200 (loss)
Total savings after 20 years (Net Present Value)1:  -$4,000 (loss)  -$6,000 (loss)  -$8,600 (loss)


Pay cash upfront
Estimated upfront cost:  $13,400  $26,900  $52,400
Net cost after tax credit:  $9,000  $17,900  $34,900
Total savings after 20 years (Simple Savings)1: $1,700 Breakeven at 17 years $6,400 Breakeven at 15 years $16,900 Breakeven at 14 years
Total savings after 20 years (Net Present Value)1: -$1,400 (loss) Breakeven beyond 20 years -$700 (loss) Breakeven beyond 20 years $1,800 Breakeven at 20 years

*Average monthly bill costs are based on Idaho Power residential Schedule 01 rates as of Nov. 1, 2020. System production estimates are from PVWatts default system settings for Boise ID. All other estimates regarding cost and payback are from Google’s Project Sunroof, which are based on current electric rates. Future changes in rates will impact the estimated net savings and payback. Project Sunroof uses a 20-year loan term and 6.6% interest rate. Actual costs, system production and tax credits will vary. For a personalized estimate, Idaho Power recommends getting several bids from certified installers.

1Why does Project Sunroof provide two different 20-year values?

Simple savings, or the payback method, and net present value are different ways of looking at the long-term value of a purchase. Payback tells you how long it takes to recoup your money. Net present value determines if it is a good financial investment compared to other things you could do with your money—like earning interest in your bank account or investing in stocks and bonds.