Running cost comes down to wattage, hours and your rate. In Hawaii the rate is 52.00 cents per kWh, which is 182.0 percent above the national average. Here is what that means for a level 2 ev charger.
A level 2 ev charger drawing 7,200 W costs $3.74 per hour in Hawaii. Run 4 hours a day that is $14.98 daily, $449 a month and $5,466 a year, which is $3,528 more than the same appliance at the US average rate.
Level 2 EV charger cost at Hawaii rates
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Planning estimate. The rate box is prefilled with a regional average; the figure on your own bill is the one that matters. Power is draw while running, not while switched on.
Cost by hours used per day in Hawaii
| Hours/day | Energy | Per day | Per month |
|---|---|---|---|
| 1 h | 7.20 kWh | $3.74 | $112 |
| 2 h | 14.40 kWh | $7.49 | $225 |
| 4 h | 28.80 kWh | $14.98 | $449 |
| 6 h | 43.20 kWh | $22.46 | $674 |
| 8 h | 57.60 kWh | $29.95 | $899 |
| 12 h | 86.40 kWh | $44.93 | $1,348 |
| 24 h | 172.80 kWh | $89.86 | $2,696 |
Cost by wattage at 52.00 cents
| Rated power | Per hour | Per day | Per month |
|---|---|---|---|
| 3,300 W | $1.72 | $6.86 | $206 |
| 5,000 W | $2.60 | $10.40 | $312 |
| 7,200 W | $3.74 | $14.98 | $449 |
| 9,600 W | $4.99 | $19.97 | $599 |
| 11,500 W | $5.98 | $23.92 | $718 |
Find the row matching the nameplate on your own unit. Within a single appliance category the spread is often wider than the difference between categories, so the label is worth reading.
Charging an EV in Hawaii
At the Hawaii rate, home charging works out well below the equivalent cost of gasoline for almost any vehicle. Cold weather reduces efficiency, since the battery is heated before and during charging, so winter cost per mile in Hawaii runs above the annual average.
Why Hawaii pays what it does
Hawaii is a regulated market, so your utility is the only supplier and the rate is set through the state commission rather than by competition. Pricing tends to be steadier than in deregulated states, and there is no switching decision available. The levers are all on your side of the meter.
At 52.00 cents, Hawaii ranks 51 of 51 from cheapest to most expensive. The West regional average is 19.65 cents. Roughly half of any residential bill is transmission and distribution rather than generation, which is why rates keep climbing even when fuel prices fall.
How this compares across the country
The same level 2 ev charger on the same schedule, in the cheapest and dearest states:
| State | Rate | Per month | Per year |
|---|---|---|---|
| Idaho | 12.35¢ | $107 | $1,298 |
| Utah | 12.96¢ | $112 | $1,362 |
| Hawaii | 52.00¢ | $449 | $5,466 |
| California | 33.25¢ | $287 | $3,495 |
| Hawaii | 52.00¢ | $449 | $5,466 |
Lowering the number in Hawaii
- Charge on an off-peak or EV tariff if one exists. This is the easiest load in the house to shift, and the savings are large.
- Set the schedule in one place only. Conflicting car and charger schedules are the usual reason people wake to an uncharged car.
- Charge to 80 percent for daily use. Better for the pack and it avoids the slow final phase.
- Precondition while plugged in. Heating the cabin from the grid rather than the battery preserves range.
- Do not pay for a bigger charger than the car accepts. Many vehicles cap AC charging at 7.2 kW.
Offsetting it with solar in Hawaii
This load uses about 28.80 kWh a day. Covering that would take roughly 20 standard 400 W panels at typical sun hours, an array of about 8.00 kW. Because it offsets electricity worth 52.00 cents rather than the national 18.44 cents, the same array is worth more here than the national payback figures suggest.
An EV is a large flexible battery that can absorb surplus solar all afternoon. Solar-aware chargers do this automatically. Full sizing, including battery and inverter requirements, is on the solar sizing page for this appliance.