Over 325 days the wall connector put 3,602 kWh into the car — 14% of everything the house used, and 18% of everything the panels made. That much is measured directly: the charger reports its own draw.
Whether the sun supplied it is a harder question, and the short answer is no. Only 22% of that charging occurred while the array was generating: the vehicle is plugged in on return from work and draws through the evening.
Billing is on a flat rate, so the bill is struck on net import over the period and no kilowatt-hour is attributable to a particular source. What can be stated is the share of total household consumption the array offsets, and what the vehicle contributes to the remainder.
Both curves are totals for the whole record, by hour of the day. They barely overlap. Charging peaks at nine in the evening, by which time the panels have been idle for hours, and 74% of it happens between 6pm and 6am.
So the array does not fuel this car in any literal sense. What it does is pay for it, which is a different claim and the one the rest of this page is about.
The vehicle is scheduled to precondition its cabin before a weekday departure. While it is plugged in, the wall connector supplies that load, so it appears in the charging record.
Between four and eight in the morning the charger draws 15 times as much energy per weekday as per weekend day. Evenings run the other way, busier at weekends. Monday and Friday resemble the weekend rather than Tuesday, consistent with departures on three days of the week.
Below 20°F the morning window draws several kilowatt-hours on most weekdays. Above 50°F it is absent. There is no corresponding rise at high temperatures, so the load is cabin and battery heating rather than cooling.
Winter efficiency is an alternative explanation and is ruled out. An electric vehicle does consume more energy per mile in cold weather, and total daily charging here roughly triples in winter, so a fixed state-of-charge target would also produce more morning charging on cold days. However, across 41 cold weekend mornings this window contains no energy at all. Ambient temperature does not vary by day of the week.
Billing is on a flat rate, so kilowatt-hours are fungible: the bill is struck on net import over the period and no kilowatt-hour is attributable to a particular source. The question with an answer is what share of total consumption the array offsets.
Over the twelve months to September 2026 the array generated 73% of household load. The house remains a net importer of 5,740 kWh across that period. The vehicle accounts for 17% of load, or 3,602 kWh.
Without the vehicle the house would import roughly 2,139 kWh instead.
Billing over the twelve months came to $1,557. Of that, $390 is fixed: a daily basic service charge plus a Customer Benefit Contribution levied per kilowatt of installed capacity, neither avoidable by using less. Dividing the remainder by net import gives a marginal rate of $0.203 per kWh.
At that rate the vehicle's 3,602 kWh costs $733 for the year.
The gross and net figures are the same, and that is the finding. Net metering credits exports against imports, so a kilowatt-hour exported in June pays for one imported in January. But the house imports more than it exports over the year, so every credit is already spent offsetting other consumption and none remains to offset the vehicle. Each kilowatt-hour it draws is an additional kilowatt-hour bought at the retail rate. Were the house a net exporter, charging would be free at the margin until the surplus ran out; it is not.
The rate is inferred from bills rather than read off the tariff, because the tariff's Power Supply Charge is republished monthly and is not in the rate guide. It is computed annually: credits bank and carry, so a single month's bill reflects the running balance rather than that month's meter.
The utility offers a time-of-day rate whose overnight band its own guide calls intended for electric vehicle charging. It runs from 10pm to 6am, and it is priced at less than half the flat rate. On its face it suits a house that charges a car overnight.
Credits net within a band and not across bands, so energy exported at noon offsets consumption at noon only. An array generates between sunrise and sunset, so over the record it exported 25 kWh into the overnight band against 6,219 kWh imported from it.
Under that rate 754 kWh of credit would remain in bands with no consumption left to offset, while the overnight band was billed in cash. The flat rate has a single band, so every exported kilowatt-hour offsets any imported one. The installation is billed on the flat rate for this reason.
The pale part of each bar is the share credited to solar. Summer does better: in June the sun is still up at eight in the evening, and the batteries start the night with more in them.
One mark per session, placed at the hour it began and sized by how much went in. A session ends when the charger has been idle for half an hour.
Most sessions are small. A car that is plugged in every night is rarely low when it starts charging, so most sessions are top-ups rather than full charges.