Solar + EV integration
Five years is enough time for gas and grid prices to genuinely move. Add your driving, offset, and rate assumptions for a year-by-year savings table over that window.
How it works
Step 1
Historical averages are a reasonable starting point, but future prices genuinely can't be predicted, so avoid overly optimistic assumptions.
Step 2
Check the 10-year projection tool to see how the picture extends beyond this 5-year window.
Step 3
This projects fuel cost savings only, not a full financial comparison including EV versus gas vehicle purchase price differences.
Gas and grid electricity prices have historically tended to rise over time, while solar panel output only degrades a small amount each year, commonly cited around 0.5% annually for modern panels. Since price increases on the gas and grid side usually outpace the modest reduction in effective solar offset from panel degradation, the dollar value of solar-charged EV driving compared to gas tends to grow modestly year over year rather than remaining constant.
The specific escalation rates used for gas price, grid rate, and solar degradation, checked in more depth with the panel degradation calculator, meaningfully affect the projected total, so it's worth using figures you're reasonably comfortable with rather than defaults you haven't considered. Conservative, well-reasoned assumptions produce a more trustworthy projection than optimistic ones that might not hold up over the actual 5-year period.
This tool projects fuel cost savings only, isolating the ongoing cost difference between solar-charged EV driving and gas vehicle driving. It doesn't include the EV's purchase price compared to a gas vehicle, financing costs, insurance differences, or maintenance cost differences, all of which matter for a truly complete financial picture but fall outside the scope of this specific fuel cost projection.
A 5-year window aligns well with common vehicle financing terms and gives a near-term view useful for budgeting decisions without extending so far into the future that the underlying assumptions become highly speculative. For a longer-horizon view better suited to comparing against a solar loan term or typical payback period, the 10-year projection tool extends this same analysis further out.
Take your total 5-year savings figure into the payback vs gas savings comparison if you haven't already found your specific payback year, or extend the view with the 10-year projection tool for a longer-term perspective. Worth pairing this with the year by year savings breakdown tool.
Questions
In a typical example with 30 miles of daily driving, 80% solar offset, and reasonable annual price escalation, 5-year cumulative savings came to about $5,460 versus continuing to drive a 30 mpg gas vehicle. Annual savings actually grow slightly each year as gas and grid prices rise faster than solar output degrades.
Gas and grid electricity prices tend to rise over time, while solar panel output only degrades a small amount each year, typically around 0.5%. Since gas price increases usually outpace the modest reduction in solar offset from panel degradation, the dollar value of driving on solar-charged electricity instead of gas tends to grow year over year.
This tool lets you set your own assumptions, but reasonable starting points are around 3% annual grid rate increases, 2.5% annual gas price increases, and 0.5% annual solar panel degradation, based on commonly cited historical averages. Actual future rates will vary and can't be predicted with certainty.
A 5-year projection is useful for near-term budgeting and financing decisions, while the 10-year projection tool gives a longer view better suited to comparing against a solar system's typical loan term or payback period. Many people find it helpful to check both for a fuller financial picture.
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