Wattfull is built to behave like a transparent advisor. The site should show what it knows, where the number came from, how fresh it is, and what would have to change for the recommendation to change.
Trust center status
Core EV engineCanonical
Calculator, SEO pages, and advisory responses share one core EV engine.
Policy layerEstimated
Policy and incentives still require direct verification before purchase.
Solar layerDirectional
Useful for screening, not an installer-grade engineering quote.
Wattfull Verdict
Wattfull is designed to be decision support, not opaque contentMixed live + estimated system
The product goal is to help users narrow expensive decisions with transparent assumptions, visible data labels, and clear next actions instead of hiding the methodology behind a single score.
Why
- Major calculators are moving toward reusable verdict and trust patterns.
- The EV stack now uses a shared calculation engine instead of fragmented page logic.
- Methodology, data labels, and caveats are first-class product surfaces.
Caveats
- Several state and solar layers remain estimated or static rather than live.
- Insurance, depreciation, and installer quotes are not personalized yet.
What would change this
- Utility-specific rates and better incentive ingestion would materially raise trust.
- More regression tests would lower the risk of calculation drift.
Canonical engine
EV calculator, SEO pages, and advisory responses share the same core math.
Transparent assumptions
Inputs, rates, incentives, and fallback values should be visible in the result context.
Trust labels
Every major number should be marked as live, estimated, static, or illustrative.
Additive updates
The product favors surgical improvements instead of broad rewrites that obscure behavior.
Resolve ZIP to state context, then load available energy-rate and incentive assumptions.
Estimate EV energy cost from kWh/100mi, charging mix, climate pressure, and annual miles.
Estimate gas cost from MPG, gas price, and annual miles.
Separate upfront cost, annual operating cost, mileage-aware maintenance, repair reserve, total ownership cost, and cost per mile before generating a verdict.
Treat a paid-off vehicle's past purchase payments as sunk cost while still counting its future energy, tires, service, and repair exposure.
Data sources and freshness
The site mixes live integrations, maintained state seeds, and static reference data. This table is meant to make that visible.
Source
Used for
Refresh cadence
Current label
Trust note
EIA
Residential electricity rates
Monthly
Estimated state seed
Used for EV and solar assumptions when ZIP-specific live utility data is unavailable.
EPA / fueleconomy.gov
Vehicle efficiency and MPG
Model year
Live spec source
Primary source for EV kWh/100mi and gas MPG assumptions.
AAA Your Driving Costs 2025
Maintenance, repair, and tire baselines
Annual
Estimated category model
Powertrain/body-class averages include scheduled maintenance, expected wear repair, and replacement tires; they are not quotes for a specific car.
DOE / Argonne
Vehicle lifespan context
Periodic research
Estimated category model
Modeled median lifetimes by body class provide context, not a hard retirement mileage or date.
NHTSA
Model-year complaints and recalls
Ongoing
Live lookup link
Complaint and recall records are linked for investigation but are not converted into failure probabilities or automatic costs.
NREL
Solar production and sun-hours
Periodic
Static sample
Used for directional solar ROI, not a roof-specific engineering study.
DSIRE / policy snapshots
State incentives and net metering
Quarterly-ish
Estimated policy layer
Policies can change faster than the current snapshot and should be verified before purchase.
AAA / fuel datasets
Gas price context
Frequent
Estimated state seed
Used as a state-level operating-cost baseline.
Calculation architecture
Wattfull centralizes EV calculation logic in one engine, then adapts that output into the EV tool, SEO pages, and advisory responses. That reduces drift, keeps assumptions aligned, and makes future testing cheaper and safer.
Editorial and affiliate policy
Product links can be affiliate links, but methodology, product framing, and calculator outputs should remain separated from merchant influence. Useful beats spam, and trust beats conversion tricks.