← Back to Ownership Guide ← Back to Transport
Build the Charging Budget From Your Real Mix
EV charging cost is not one electricity rate. It is the amount of electricity billed at home, shared-residential, public AC and fast DC chargers, plus any charging-specific parking, access, subscription or idle fees.
Start with delivered electricity—the kWh you pay for—rather than a brochure range or battery size.
Monthly budget formula
(Annual km × delivered kWh/100 km ÷ 100 × weighted S$/kWh + annual charging fees) ÷ 12.
1) Separate vehicle use from delivered electricity
Assume an EV reports 16.5 kWh/100 km at the vehicle but charging records show 18.2 kWh/100 km billed at the electricity boundary. The difference represents a hypothetical 10.3% uplift from vehicle use to delivered energy:
18.2 ÷ 16.5 − 1 = 10.3%.
This is an example, not a universal loss rate. Temperature, charging power, battery conditioning and how each system measures energy can change it. Use billed or metered kWh divided by kilometres whenever you have several weeks of records.
2) Record every charging channel
| Channel | Price evidence | Extra cost to check |
|---|---|---|
| Household supply | Electricity bill or retail plan | Charger installation, registration, inspection and maintenance |
| Shared residential | Operator app or MCST arrangement | Subscription, access rules and idle fees |
| Public AC | Operator's displayed tariff | Parking paid only because of charging |
| Fast DC | Operator's displayed tariff | Idle fees, detour and deliberate waiting time |
MyTransport.SG provides publicly accessible charging locations, real-time availability and charger information. Check the operator's current terms before using a displayed rate in a long-term budget.
3) Work a monthly mixed-charging example
Assume 16,000 km a year and 18.2 delivered kWh/100 km. Annual delivered electricity is:
16,000 × 18.2 ÷ 100 = 2,912 kWh.
Use this hypothetical mix:
- 60% at home at S$0.3478/kWh, the EMA regulated household tariff including GST for July–September 2026;
- 30% at public AC charging at an example S$0.55/kWh; and
- 10% at fast DC charging at an example S$0.75/kWh.
Weighted rate = (60% × S$0.3478) + (30% × S$0.55) + (10% × S$0.75) = S$0.44868/kWh.
| Mixed budget | Calculation | Amount |
|---|---|---|
| Annual electricity | 2,912 × S$0.44868 | S$1,306.56 |
| Charging-specific fees | Example access and parking | S$120/year |
| Annual charging budget | S$1,306.56 + S$120 | S$1,426.56 |
| Monthly charging budget | S$1,426.56 ÷ 12 | S$118.88 |
The household tariff changes quarterly, and the two public rates are hypothetical. Replace all three with rates you can document on the same date.
4) Compare charging patterns on the same energy
| Illustrative pattern | Energy rate | Annual energy | Monthly energy |
|---|---|---|---|
| All household supply | S$0.3478/kWh | S$1,012.79 | S$84.40 |
| Mixed case above | S$0.44868/kWh | S$1,306.56 | S$108.88 |
| All public AC example | S$0.55/kWh | S$1,601.60 | S$133.47 |
| All fast DC example | S$0.75/kWh | S$2,184 | S$182 |
These rows exclude setup, subscriptions, parking and idle fees. They show why “EV electricity is cheap” is incomplete unless the price mix is named.
5) Price connected time and deliberate time separately
The example EV needs 2,912 kWh a year, or 56 kWh in an average week. At a constant 7.4 kW, that energy has a theoretical minimum of about 7.6 connected hours. At 50 kW, the theoretical minimum is about 1.1 hours. Actual charging can take longer because the vehicle may accept less than the charger's rating and power can taper.
Connected time is often harmless when the car is parked anyway. Deliberate time is different: detouring, waiting for a bay, returning to move the car or ending an idle-fee window. Record the minutes that would not exist without charging.
6) Keep a four-week charging ledger
| Record after every session | Why it matters |
|---|---|
| Delivered kWh and amount paid | Produces the effective S$/kWh |
| Odometer distance since the prior session | Produces delivered kWh/100 km |
| Charger type, rated power and location | Shows the actual channel mix |
| Parking, access, subscription and idle fees | Captures costs outside the energy tariff |
| Deliberate detour and waiting minutes | Separates background charging from a new errand |
| Failed or unavailable sessions | Tests whether the routine needs a stronger fallback |
Use the ledger in the five-year EV-versus-petrol comparison. If the mix depends on public access, compare cash and time together.
FAQ
How do I calculate monthly EV charging cost?
Multiply annual kilometres by delivered kWh per 100 km, divide by 100, multiply by the weighted charging price, add charging-specific fees, then divide by 12.
Should I use the household electricity tariff for all EV charging?
Only for the share actually billed that way. Public and shared-residential chargers can have operator tariffs, parking charges, subscriptions or idle fees.
Why is delivered electricity higher than dashboard consumption?
Energy can be lost between the meter and battery through the charging equipment and vehicle systems. Use metered or billed kWh where available, or state a loss assumption.
Does a faster charger always reduce charging cost?
No. Power affects connected time, while the tariff and fees determine cash cost. The car may also accept less than the charger's maximum rating and reduce power as the battery fills.
Sources
- Energy Market Authority — Regulated household electricity tariff
- Land Transport Authority — Charging availability and EV transition
- Land Transport Authority — MyTransport.SG charger information
- Land Transport Authority and Enterprise Singapore — SS 722 charging standard
Last updated: 25 Sep 2026 · Editorial Policy · Advertising Disclosure · Corrections