Sri Lanka EV Charging Cost Calculator

The calculator follows a six-step pipeline drawn from standard EV charging engineering and the PUCSL Retail Tariff Determination — March 2025. Every constant on the page traces back to a regulator publication — CEB and LECO bill the same PUCSL-approved schedule, so the figures apply nationwide for household connections.

Step 1 — energy per charge

The usable energy you put into the pack per charging session is the state-of-charge swing multiplied by usable battery capacity: energy_to_battery_kWh = (to% − from%) ÷ 100 × battery_kWh. A 40 kWh Nissan Leaf charged from 20% to 90% takes in 28 kWh.

Step 2 — energy drawn from the grid

A home AC charger is not 100% efficient. The on-board charger converts AC to DC, the cells warm under load, and the BMS trickles charge near the top — the losses end up on your CEB bill even though they never reach the battery. The calculator defaults to 90% charger efficiency, which is typical for a single-phase wall-box on a 32 A line. grid_kWh = energy_to_battery_kWh ÷ (charger_eff ÷ 100).

Step 3 — monthly charging energy

Range added per charge is the battery energy times the vehicle's mixed-driving efficiency (km per kWh — not WLTP, which overstates). Charges per month is monthly distance divided by range per charge, and monthly grid energy is charges per month times grid kWh per charge. For our Leaf at 50 km/day, that's 10.7 cycles a month and roughly 333 kWh added to the bill.

Step 4 — bill on the block (D-1) tariff

The Domestic D-1 tariff is retroactive: the slab is picked from your total monthly units, and the slab's rates apply across the entire bill — not just the units above the previous slab's ceiling. To get the true marginal EV cost the calculator runs your existing usage through the full PUCSL slab schedule once, then again with the EV load added, and takes the difference. That's the same authoritative slab logic used by the Sri Lanka electricity bill calculator on this site — one source of truth across both pages.

Step 5 — bill on the Time-of-Use (D-TOU) tariff

D-TOU prices each unit at the rate of the band in which it was drawn and adds a Rs 2,000 monthly fixed charge for the TOU meter. The three bands published by PUCSL are:

• Day (05:30 – 18:30) — Rs 36/kWh
• Peak (18:30 – 22:30) — Rs 58/kWh
• Off-Peak (22:30 – 05:30) — Rs 18/kWh

Off-peak is the cheapest band on the schedule by a wide margin and is what nearly every EV owner uses — charging is automatable through the car's own departure-time scheduler, no separate timer needed. Peak is more than three times the off-peak rate, so the calculator flags it visibly when picked.

Step 6 — equivalent petrol or diesel cost

The ICE comparison runs the same monthly distance through your chosen car's fuel economy at the current CPC pump price: ice_cost = monthly_km ÷ ice_km_per_L × price_per_L. Default is Petrol 92 at the CPC rate verified on 2026-05-17; you can switch to Petrol 95, Auto Diesel, or Super Diesel. Monthly savings is the ICE cost minus the EV tariff cost, and annual savings is twelve times that — useful for comparing against the EV's purchase premium over a like-for-like ICE.

Cross-check: the direct-formula path

The page exposes a calculateMonthlyGridKwhByDirectFormula helper that derives monthly grid kWh in a single expression — (daily_km × 30 ÷ km_per_kWh) ÷ charger_eff — without the per-charge intermediate. Both paths agree to within rounding, which is how the data module verifies its own arithmetic at typecheck time.

What the calculator does not cover

Public DC fast-charging (ChargeNet, LECO EV stations, third-party operators) is priced per operator and updated often — out of scope. Battery degradation is non-deterministic and varies by chemistry — out of scope; the efficiency input lets you model a degraded pack manually by lowering km/kWh. Three-phase wiring upgrade cost and loan EMI for the EV purchase itself are quoted by your electrician and bank respectively — use the loan EMI calculator for the latter. Solar self-consumption credit is handled by the solar net metering calculator.

Three scenarios across the most common EV/usage combinations in Sri Lanka, worked end-to-end. Try plugging each set of inputs into the calculator above — the numbers should match what you see.

• PUCSL — Retail Tariff Determination (March 2025, in force)
• Ceylon Electricity Board — Tariff Information
• Ceylon Electricity Board — Electricity Bill information
• Ceylon Petroleum Corporation — Retail Fuel Prices
• Department of Motor Traffic — Vehicle classification reference

Tariffs and fuel prices on this page were last cross-checked on 2026-05-17. The page is reviewed whenever PUCSL publishes a new tariff determination or CPC issues a monthly fuel revision.