BoltMeter
virtual EV submeterDisaggregated from whole-home Enphase data · no hardware on the circuit · May 2025 – May 2026
Annual charging cost
$1,130
$1276 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
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.
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)
$1,130
12.7¢ / mile
grid cost after baseline credits · 80 kWh solar-sourced at $0
⛽ Gas would've cost
~$1,378
296 gal × $4.65 · 30 MPG car
✓ You saved
$249
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
12.7¢
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
$1,130/yr
12.7¢/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
8 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
+60% overall delta — expected, not an error
Dec, Jan are missing solar backfill data, so Enphase shows gross consumption without the solar offset. Once the June budget reset runs the backfill, this will collapse to ~2–3%.
Solar data note: Production backfill covers Feb 2026–present. Months before that show 0% solar — actual solar contribution for May–Jan was small but non-zero. Full backfill completes after June 2026 API budget reset.