EV Home Charging Cost Calculator (Arizona APS/SRP Rate Plans)
Estimate your monthly electric vehicle home charging costs under Arizona Public Service (APS) and Salt River Project (SRP) rate plans, including standard, time-of-use (TOU), and EV-specific rates.
Formulas Used
1. Grid Energy Required (kWh/month):
kWh_grid = (Miles ÷ Vehicle_Efficiency_mi_per_kWh) ÷ (Charger_Efficiency% ÷ 100)
2. Flat Rate Plans:
Monthly_Cost = kWh_grid × Rate_$/kWh
3. Time-of-Use Plans:
Effective_Rate = (Off_Peak% × Off_Peak_Rate) + (On_Peak% × On_Peak_Rate)
Monthly_Cost = kWh_grid × Effective_Rate
4. TOU + Demand Charge Plans:
Monthly_Cost = (kWh_grid × Effective_Rate) + (Charger_kW × Demand_$/kW)
5. Seasonal Weighted Average:
Avg_Monthly = (Summer_Cost × 4/12) + (Winter_Cost × 8/12)
Arizona summer = June–September (4 months); winter = October–May (8 months).
Assumptions & References
- Rates are approximate 2024 values sourced from APS and SRP published tariff schedules. Always verify current rates directly with your utility.
- APS Plans: Saver Choice (flat), Saver Choice Plus (TOU), EV Advantage (EV TOU), Saver Choice Peak (TOU+Demand). See aps.com rate plans.
- SRP Plans: Basic (E-13), Time-of-Use (E-26), EV Price Plan (E-23), TOU with Demand (E-27). See srpnet.com EV plans.
- Arizona summer season: June–September (4 months); winter: October–May (8 months).
- Charger efficiency accounts for AC-to-DC conversion losses (Level 2 ~85–95%, Level 1 ~80–85%).
- Demand charges apply to the highest 15-minute or 30-minute peak kW interval in the billing period. This calculator uses charger rated power as a proxy.
- Monthly cost does not include fixed service/meter charges (typically $10–$20/month).
- Vehicle efficiency varies with temperature, driving style, speed, and HVAC use. EPA-rated efficiency used as baseline.
- Off-peak charging percentage is user-defined; maximizing off-peak charging (especially midnight–6 AM) yields greatest savings on TOU plans.