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Sri Lanka Time-of-Use (TOU) Electricity Tariff Calculator

Wondering if a CEB or LECO Time-of-Use meter is worth it? Enter your off-peak, day and peak units and this tool compares the Domestic TOU bill against the standard block tariff for the same usage — so you know whether to switch. No signup, sources cited below.

By Induwara AshinsanaUpdated Jun 13, 2026
Is a TOU meter worth it?
PUCSL D-TOU · Jan 2025

22:30 – 05:30

05:30 – 18:30

18:30 – 22:30

Try a profile

A TOU meter saves you Rs 14,020/month

That is about 50.76% off your current standard bill for the same 400 units. Applying for a D-TOU meter looks worth it.

TOU bill
Rs 13,600
Standard bill
Rs 27,620
Slab F
You save
Rs 14,020
Total units
400 kWh

TOU cost by period

Off-Peak
Rs 3,000
Day
Rs 4,200
Peak
Rs 4,400
ChargeUnitsRateAmount
Off-Peak energy200Rs 15.00Rs 3,000
Day energy120Rs 35.00Rs 4,200
Peak energy80Rs 55.00Rs 4,400
Fixed charge—flatRs 2,000
TOU totalRs 13,600

Break-even hint

At 400 total units, TOU beats the standard tariff for any day/peak split — even if every unit were used in the peak window.

PeriodHoursRate (Rs/kWh)
Off-Peak22:30 – 05:30 (7h)15.00
Day05:30 – 18:30 (13h)35.00
Peak18:30 – 22:30 (4h)55.00

Rates: Off-Peak Rs 15.00, Day Rs 35.00, Peak Rs 55.00 per kWh, plus a flat Rs 2,000 fixed charge — PUCSL Domestic Time-of-Use schedule (Jan 2025). Standard-tariff comparison uses the same PUCSL determination as the SL Electricity Bill Calculator. Verified 2026-06-13.

How it works

Sri Lanka's Domestic Time-of-Use (D-TOU) tariff is an optional alternative to the standard block tariff. Instead of one rate ladder driven by your total monthly units, it prices each unit by when you use it, across three windows set by the Public Utilities Commission of Sri Lanka (PUCSL):

  • Off-Peak: 22:30 – 05:30 (7h) — Rs 15.00/kWh
  • Day: 05:30 – 18:30 (13h) — Rs 35.00/kWh
  • Peak: 18:30 – 22:30 (4h) — Rs 55.00/kWh

The monthly TOU bill is straightforward and slab-free:

Bill = (off × 15) + (day × 35) + (peak × 55) + 2,000

The comparison is what matters. The standard domestic tariff is retroactive: your total units decide which slab you fall into, and that slab's full rate ladder then applies to every unit. Cross 180 units and you land in the top slab, where the highest block costs Rs 75/kWh. A heavy user with shiftable load (an EV, a water heater, a pump) can avoid that ladder entirely by moving consumption into the off-peak window at Rs 15/kWh. That is the single biggest reason TOU helps — and the reason small, evening-concentrated households are usually better off on the standard tariff, because the Rs 2,000 fixed charge and Rs 55 peak rate outweigh any off-peak saving.

To keep both sides consistent, the standard-tariff figure here is computed by the same PUCSL-determination engine used by our Sri Lanka Electricity Bill Calculator, so the two tools always agree to the rupee. The calculator also derives a break-even: holding your total units fixed, it solves for the peak-period kWh at which the two tariffs cost the same, trading peak against off-peak. That tells you how much evening load you would need to move overnight before TOU starts paying off. Every rate is the PUCSL January 2025 determination (effective Jan 18, 2025), last verified 2026-06-13; re-confirm against your own bill before applying for a meter change.

Worked examples

EV owner, charges overnight — 400 units (200 off / 120 day / 80 peak)

TOU saves Rs 14,020 / month

  1. TOU energy: 200×15 + 120×35 + 80×55 = 3,000 + 4,200 + 4,400 = Rs 11,600
  2. TOU total: 11,600 + 2,000 fixed = Rs 13,600
  3. Standard (slab F): 60×42 + 60×50 + 60×60 + 220×75 = Rs 25,620
  4. Standard total: 25,620 + 2,000 fixed = Rs 27,620
  5. Verdict: 27,620 − 13,600 = TOU saves Rs 14,020/month

Small evening-heavy user, no EV — 120 units (15 off / 35 day / 70 peak)

TOU costs Rs 3,660 more / month

  1. TOU energy: 15×15 + 35×35 + 70×55 = 225 + 1,225 + 3,850 = Rs 5,300
  2. TOU total: 5,300 + 2,000 fixed = Rs 7,300
  3. Standard (slab D): 60×12 + 30×28 + 30×36 = Rs 2,640
  4. Standard total: 2,640 + 1,000 fixed = Rs 3,640
  5. Verdict: 3,640 − 7,300 = TOU costs Rs 3,660 MORE/month

Just over the top-slab line — 181 units (100 off / 50 day / 31 peak)

TOU saves Rs 4,240 / month

  1. TOU energy: 100×15 + 50×35 + 31×55 = 1,500 + 1,750 + 1,705 = Rs 4,955
  2. TOU total: 4,955 + 2,000 fixed = Rs 6,955
  3. Standard (slab F floor): 60×42 + 60×50 + 60×60 + 1×75 = Rs 9,195
  4. Standard total: 9,195 + 2,000 fixed = Rs 11,195
  5. Verdict: 11,195 − 6,955 = TOU saves Rs 4,240/month — the slab-F cliff is what tips it

Frequently asked questions

Sources & references

The TOU rates, time windows and fixed charge were last cross-checked against the PUCSL January 2025 determination on 2026-06-13. The standard-tariff comparison reuses the same PUCSL determination basis as the Sri Lanka Electricity Bill Calculator. This page is reviewed after every PUCSL tariff revision.

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