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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 7,130/month

That is about 23.49% off your current standard bill for the same 400 units. Applying for a D-TOU meter looks worth it.

TOU bill
Rs 23,220
Standard bill
Rs 30,350
Slab F
You save
Rs 7,130
Total units
400 kWh

TOU cost by period

Off-Peak
Rs 6,600
Day
Rs 5,640
Peak
Rs 8,480
ChargeUnitsRateAmount
Off-Peak energy200Rs 33.00Rs 6,600
Day energy120Rs 47.00Rs 5,640
Peak energy80Rs 106.00Rs 8,480
Fixed charge—flatRs 2,500
TOU totalRs 23,220

Break-even hint

Break-even peak usage is about 178 kWh (44.42% of total). Your current peak usage is already below this, so TOU works in your favour.

PeriodHoursRate (Rs/kWh)
Off-Peak22:30 – 05:30 (7h)33.00
Day05:30 – 18:30 (13h)47.00
Peak18:30 – 22:30 (4h)106.00

Rates: Off-Peak Rs 33.00, Day Rs 47.00, Peak Rs 106.00 per kWh, plus a flat Rs 2,500 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 2026-09-23.

Time-of-Use got less attractive on 11 May 2026 — for most households

Both sides of this comparison are on the tariff PUCSL approved with effect from 11 May 2026: Domestic Time-of-Use at peak Rs 106.00, day Rs 47.00, off-peak Rs 33.00 with a Rs 2,500 monthly fixed charge, and the standard tariff's three consumption bands. The catch is what happened to the standard side: once a household passes 180 units, its first 180 units are re-priced down to Rs 32.50 each. A peak unit on TOU costs Rs 106. So an ordinary evening-heavy household that used to break even on TOU now loses on it, and two of the worked examples below reversed sign at this revision.

Time-of-Use still wins clearly for one shape of household: a large load you can genuinely move into 22:30–05:30, such as overnight EV charging. Put your own split in above — that is the only answer that counts. Check the rates against PUCSL's own table.

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 33.00/kWh
  • Day: 05:30 – 18:30 (13h), Rs 47.00/kWh
  • Peak: 18:30 – 22:30 (4h), Rs 106.00/kWh

The monthly TOU bill is straightforward and slab-free:

Bill = (off × 33) + (day × 47) + (peak × 106) + 2,500

The comparison is what matters. The standard domestic tariff is retroactive: your total units decide which consumption band you fall into, and that band's full rate ladder then applies to every unit. Cross 180 units and you land in the top band, where units above 180 cost Rs 100/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 33/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 2,500 fixed charge and Rs 106 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 on both sides is the PUCSL determination approved with effect from May 11, 2026), last verified 2026-09-23; 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 7,130 / month

  1. TOU energy: 200×33 + 120×47 + 80×106 = 6,600 + 5,640 + 8,480 = Rs 20,720
  2. TOU total: 20,720 + 2,500 fixed = Rs 23,220
  3. Standard (above 180): 180×32.50 + 220×100 = Rs 27,850
  4. Standard total: 27,850 + 2,500 fixed = Rs 30,350
  5. Verdict: 30,350 − 23,220 = TOU saves Rs 7,130/month
  6. On the pre-11-May-2026 rates this same household saved Rs 14,020, the revision took half the advantage away.

Heavy user with a genuinely shiftable load, 600 units (400 off / 150 day / 50 peak)

TOU saves Rs 22,300 / month

  1. TOU energy: 400×33 + 150×47 + 50×106 = 13,200 + 7,050 + 5,300 = Rs 25,550
  2. TOU total: 25,550 + 2,500 fixed = Rs 28,050
  3. Standard (above 180): 180×32.50 + 420×100 = Rs 47,850
  4. Standard total: 47,850 + 2,500 fixed = Rs 50,350
  5. Verdict: 50,350 − 28,050 = TOU saves Rs 22,300/month
  6. This is the shape TOU rewards: most of the load off-peak, very little of it in the 18:30–22:30 window.

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

TOU costs Rs 8,780 more / month

  1. TOU energy: 15×33 + 35×47 + 70×106 = 495 + 1,645 + 7,420 = Rs 9,560
  2. TOU total: 9,560 + 2,500 fixed = Rs 12,060
  3. Standard (60–180 band): 60×14 + 30×20 + 30×28 = Rs 2,280
  4. Standard total: 2,280 + 1,000 fixed = Rs 3,280
  5. Verdict: 3,280 − 12,060 = TOU costs Rs 8,780 MORE/month
  6. The Rs 2,500 fixed charge alone is most of this household's whole standard bill.

One unit into the top band, 181 units (100 off / 50 day / 31 peak)

TOU costs Rs 2,986 more / month

  1. TOU energy: 100×33 + 50×47 + 31×106 = 3,300 + 2,350 + 3,286 = Rs 8,936
  2. TOU total: 8,936 + 2,500 fixed = Rs 11,436
  3. Standard (above 180): 180×32.50 + 1×100 = Rs 5,950
  4. Standard total: 5,950 + 2,500 fixed = Rs 8,450
  5. Verdict: 8,450 − 11,436 = TOU costs Rs 2,986 MORE/month
  6. This example used to show TOU saving Rs 4,240, on the reasoning that crossing the old top slab was a cliff. Under the current schedule crossing 180 re-prices the first 180 units DOWN to Rs 32.50, the opposite of a cliff, so the case reverses.

Frequently asked questions

Sources & references

The TOU rates, time windows and fixed charge were read off Annex-2 of the determination above on 2026-09-23. The standard-tariff side is not transcribed here at all. It is computed by the same code the Sri Lanka Electricity Bill Calculator uses, so the two tools cannot drift apart. This page is reviewed after every PUCSL tariff revision.

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