Marginal-Rate EV Charging Cost Calculator
See what your EV actually adds to your bill — priced at the marginal tier and TOU rate, not the household average.
How this calculator works
This calculator estimates the marginal cost of your EV charging by comparing your pre-EV and post-EV household consumption. Instead of using a single average rate, it prices the extra kWh at the tier and time-of-use rates those kWh actually reach. The result is a modeled estimate of the EV-attributable bill increase, plus a residual that shows how much of the increase is not explained by EV charging.
The calculation starts from your pre-EV consumption level. The first EV kWh is priced at the tier the household was already in, then the next kWh move up the tier ladder. If TOU is enabled, the tool splits the EV kWh into peak and off-peak portions using your stated off-peak share and applies the TOU rates to those kWh. This is a simplified model; many utilities combine tier and TOU structures in ways that require the actual tariff sheet.
The meter measures wall kWh, not battery kWh. The observed post-EV minus pre-EV delta already includes charging losses. The charging-loss input is used only for the optional miles cross-check, which converts your driving into an estimated wall kWh using the efficiency value you provide.
Assumptions & Limitations
- This is a modeled estimate, not a utility-verified bill.
- Fixed charges, demand charges, and taxes are not included.
- Tier breakpoints and TOU windows vary by utility; verify with your tariff sheet.
- The residual may include weather, rate changes, or other household changes.
- When TOU is enabled, the calculator applies TOU rates to the EV kWh and ignores the tier structure for those kWh (simplified model).
- Results are only as accurate as the inputs; unusual tariffs may require manual interpretation.
Sources: Tiered-rate concept from the California Public Utilities Commission; average-rate benchmark from the U.S. Energy Information Administration; charging-loss range from industry/technical sources. All time-sensitive data must be verified with your utility.
Marginal-Rate EV Charging Cost Calculator
See what your EV actually adds to your bill — priced at the marginal tier and TOU rate, not the household average.
How this calculator works
This calculator estimates the marginal cost of your EV charging by comparing your pre-EV and post-EV household consumption. Instead of using a single average rate, it prices the extra kWh at the tier and time-of-use rates those kWh actually reach. The result is a modeled estimate of the EV-attributable bill increase, plus a residual that shows how much of the increase is not explained by EV charging.
The calculation starts from your pre-EV consumption level. The first EV kWh is priced at the tier the household was already in, then the next kWh move up the tier ladder. If TOU is enabled, the tool splits the EV kWh into peak and off-peak portions using your stated off-peak share and applies the TOU rates to those kWh. This is a simplified model; many utilities combine tier and TOU structures in ways that require the actual tariff sheet.
The meter measures wall kWh, not battery kWh. The observed post-EV minus pre-EV delta already includes charging losses. The charging-loss input is used only for the optional miles cross-check, which converts your driving into an estimated wall kWh using the efficiency value you provide.
Assumptions & Limitations
- This is a modeled estimate, not a utility-verified bill.
- Fixed charges, demand charges, and taxes are not included.
- Tier breakpoints and TOU windows vary by utility; verify with your tariff sheet.
- The residual may include weather, rate changes, or other household changes.
- When TOU is enabled, the calculator applies TOU rates to the EV kWh and ignores the tier structure for those kWh (simplified model).
- Results are only as accurate as the inputs; unusual tariffs may require manual interpretation.
Sources: Tiered-rate concept from the California Public Utilities Commission; average-rate benchmark from the U.S. Energy Information Administration; charging-loss range from industry/technical sources. All time-sensitive data must be verified with your utility.