BoltMeter
virtual EV submeterDisaggregated from whole-home Enphase data · no hardware on the circuit · May 2025 – May 2026
Annual charging cost
$1,120
$1263 retail before baseline & NEM credits
Share of home energy
23.7%
2,886.9 of 12,158.6 kWh
Charged off-peak
97%
2,793.1 kWh · saves ~$16/yr vs all-peak
Sessions detected
110
12-month window · algorithm-only
Your solar already covers the house. Almost everything you pay PG&E is the car — even though charging is only 23.7% of the energy you use.
Grid bill without the EV
$230
solar + house nearly net to zero
The EV adds
$1,120
counterfactual marginal cost
EV share of what you pay
83%
vs 23.7% of energy used
The $1,120 isn't a slice of your bill — it's almost the whole bill. Your panels offset nearly all of your non-car usage, so removing the car wouldn't shave 24% off what you pay — it would drop your grid bill to about $230. In your sunny months it would even flip you to a NEM credit, which is why the car can cost more than your headline out-of-pocket: it also cancels the export credits you'd otherwise bank.
Monthly Charging
kWh by source (bars) · out-of-pocket cost (line)
Click a month to see daily breakdown →
Home Charging Cost
PG&E E-TOU-C · what does it actually cost per kWh?
Overall avg
$0.39
kWh-weighted across all months · accounts for NEM credit value
Summer
$0.39
Jun–Sep · typical session
Winter
$0.43
Oct–May · typical session
Summer TOU rates are higher on paper ($0.491 vs $0.435) but cheaper in practice — solar pulls net grid import below the baseline allowance, triggering a ~$0.10/kWh credit on the whole bill.
Winter mostly sits above baseline. Jul and Apr you were a net exporter — but EV charging in those months still costs ~$0.39/kWh because it consumes NEM credit balance at retail rate (which would have offset future bills). Overall avg of $0.39is the kWh-weighted blend.
vs. public charging (CA 2025)
Home is competitive with public L2 — below the L2 midpoint by $0.01/kWh. DCFC is still more expensive.
⚠ Rates from most recent bill (Jan 2026 winter · Sep 2025 summer). PG&E adjusts rates multiple times per year.
Takeaway · charging strategy
- May–Sep: always charge at home — ~$0.39/kWh consistently, even in net-exporter months (you'd just be losing more NEM credit). Public L2 ($0.35–$0.45) can't reliably beat that.
- Oct–May: home at $0.43/kWh marginal — an L2 station under $0.40/kWh is slightly cheaper. Modest savings ($0.03–$0.08/kWh), only worth it when nearby.
- DCFC ($0.45+): more expensive than home year-round. Only worth it when time-pressed.
- NEM2.0 timing: day vs. night charging costs the same — your overnight TOU schedule is already optimal.
Net vs. baseline allowance — which side of the line?
PG&E discounts the first ~301 kWh of monthly net usage by ~$0.10/kWh. You only capture it when net usage reaches the allowance.
Discount pool available
$375/yr
if net ≥ baseline every month
You captured
$251/yr
67% of the pool
Left on the table
$124/yr
net below baseline in solar months
dashed line = baseline allowance · above = full off-peak rate · below = discount applies
Takeaway · more panels won't capture more discount
- The baseline discount is a capped pool (~$375/yr). You capture it by consuming up to the allowance — not by adding solar. You currently capture 67%.
- Adding panels moves you the wrong way for this credit: lower net → more months below baseline or exporting → less of the pool captured, and the ~$124 already wasted grows.
- The solar kink: a new kWh of solar saves the full ~$0.45 only while you're above baseline (6 winter months). Once it pushes you below, it's only worth ~$0.35 — diminishing returns, separate from the NEM2→NEM3 cliff.
- Free lever instead: in your below-baseline months (Jul, Apr, May, Jun) a marginal EV kWh slips under the allowance at ~$0.35 vs ~$0.45 in winter. Shifting discretionary charging there soaks up discount you're otherwise throwing away.
EV vs Gas — what your charging actually bought
2020 Bolt EV · CA 2025~8,900miles
estimated EV miles on 2,887 kWh metered · 2,540 kWh to battery after charging losses
⚡ You paid (EV)
$1,120
12.6¢ / mile
grid cost after baseline credits · 111 kWh solar-sourced at $0
⛽ Gas would've cost
~$1,378
296 gal × $4.65 · 30 MPG car
✓ You saved
$258
vs driving the same miles on gas
CO₂ avoided
2,634 kg
≈ 121 tree-years of absorption
SF → LA trips
23.3×
San Mateo → LA is 381 mi
Cost per mile
12.6¢
vs ~15.5¢ on gas
What if you didn't have solar?
Counterfactual · same 2,887 kWh of charging, no rooftop PV, no NEM2.0
Your actual (with solar)
E-TOU-C · NEM2.0 · baseline credits applied
$1,120/yr
12.6¢/mile
Without solar — annual cost at 2,887 kWh
EV2-A · optimal
$944
$0.33/kWh · 10.6¢/mile
Switch to EV plan · charge 12 AM–3 PM at super-off-peak
Public L2
$1,155
$0.40/kWh · 13.0¢/mile
Avg $0.40/kWh · ChargePoint, EVgo
E-TOU-C · current
$1,313
$0.45/kWh · 14.8¢/mile
Same plan you have today, but no solar offset
Gas (30 MPG)
$1,378
$0.48/kWh · 15.5¢/mile
$4.65/gal · CA 2025
Takeaway · no-solar EV owner playbook
- Switch to EV2-A — saves ~$369/year vs. staying on E-TOU-C. Schedule charging to start at midnight for 100% super-off-peak.
- Home still beats gas by ~$435/year on the best plan, ~$65/year on the default plan.
- Public L2 ($0.40/kWh) only beats home if you're stuck on E-TOU-C. On EV2-A, home is ~$0.07/kWh cheaper.
- DCFC ($0.55 avg) is never the answer for routine charging — only worth it when time-pressed.
Rate assumptions · E-TOU-C from actual bills (summer off-peak $0.49157, winter $0.4346). EV2-A approximated from PG&E tariff: super-off-peak $0.32/kWh (12 AM–3 PM), off-peak $0.5, peak $0.61/$0.5 (summer/winter). Public L2 $0.4/kWh (typical CA 2025 ChargePoint/EVgo). Charging mix: 97% off-peak, 32% summer kWh, matched to your actual usage pattern. ⚠ EV2-A rates approximate — confirm with a current bill before switching.
Validation
Validation vs ChargePoint
Algorithm-only detection vs EVSE ground truth · home sessions only
avg. kWh error per session
systematic undercount — expected
Home sessions found
17 / 17
every detectable home session
Sessions excluded
9
out-of-scope — see below
9 ChargePoint sessions not matched: 1 public charger (off-home-meter, undetectable) · 6 below 6 kW threshold · 2 edge cases
Large start offset (193 min): CP records plug-in time; TOU scheduling delays actual power draw. Not an error.
Validation vs PG&E Meter
Enphase net (consumption − solar) vs PG&E metered net import · 314 days
avg. error vs PG&E meter
12 months with complete solar data
PG&E net import
2,845 kWh
import − export · overlap period
PG&E billed
$1,282
whole-home · overlap period