Understanding road trip charging cost
Why public fast charging costs so much more than home charging
Public DC fast charging networks typically charge $0.35 to $0.60 per kWh, well above typical home electricity rates of $0.12 to $0.20 per kWh, since the equipment, site leasing, and grid connection costs for high-power public charging are substantially higher than a home Level 2 setup. Some networks also add per-session or idle fees on top of the energy cost, which this calculator accounts for separately.
Highway driving efficiency is usually worse than city driving
Aerodynamic drag increases sharply at highway speeds, so most EVs see noticeably lower efficiency on a highway road trip compared to stop-and-go city driving where regenerative braking recovers more energy. Using your normal daily efficiency figure for a road trip estimate typically understates the real cost, so adding 10 to 15% to your usual kWh per 100 miles gives a more accurate trip projection.
What the days-to-offset comparison actually means
This figure isn't suggesting solar panels somehow power a public charger down the highway. Instead, it puts a one-time road trip expense into everyday context by showing how many days of accumulated home charging savings would add up to the same dollar amount. A household saving less than a dollar a day from solar-offset home charging might see a single road trip cost the equivalent of two or three months of that daily benefit, which is a useful way to think about total household EV cost rather than treating home and road trip charging as unrelated expenses.
Road trips remain a small part of most EV owners' total charging cost
For most households, the vast majority of EV charging happens at home on routine daily driving, with road trips representing an occasional, larger single expense a few times a year at most. Solar's real financial value, explored further in the savings calculator for high usage homes, comes from consistently lowering that everyday home charging cost, not from directly affecting road trip expenses, which remain tied to whatever public charging network and pricing is available along the route.
Turning this into a decision
See your total annual home charging savings with the 5-year savings projection tool to understand the bigger financial picture beyond any single road trip comparison. Charging an EV adds real load to your system. The solar panel calculator in our System Sizing section can help you work out how many extra panels that driving needs.