Sri Lanka Appliance Electricity Cost Calculator

Two numbers decide what an appliance costs you in Sri Lanka: the energy it uses, and the slab that energy lands in. The calculator handles both, then shows the gap between them — which is where most people get a nasty surprise.

Step 1 — energy.One kilowatt-hour (kWh, or “unit”) is 1,000 watts running for one hour. The monthly energy is:

kWh/month = (watts ÷ 1000) × hours per day × days per month × quantity

Step 2 — the bill function. Domestic (D-1) billing under the PUCSL — Retail Tariff Determination, March 2025 is a retroactiveblock tariff. Your total monthly units pick one slab, and then every unit is charged on that slab's rate ladder — not just the units above the previous ceiling. The slabs run 0–30, 31–60, 61–90, 91–120, 121–180 and 181+ units, each with its own rising band rates and a fixed monthly charge. These rates are not re-typed here; the tool calls the same unit-tested engine that powers this site's CEB/LECO bill calculator, so there is a single source of truth.

Step 3 — the true marginal cost. The honest cost of an appliance is what it adds to your whole bill:

true cost = bill(baseline + appliance kWh) − bill(baseline)

This captures both the new units andthe retroactive repricing of your existing units if the extra load pushes you across a slab boundary. Dividing it by the appliance's kWh gives the effective rate — the rupees per unit you actually pay.

Step 4 — the naive sticker cost.For contrast, the tool also shows the appliance's energy priced at the single top per-unit rate that applies at your new usage level, ignoring the fixed-charge step and the repricing of existing units. When you stay inside one slab the two figures match; when you cross a boundary the gap is the slab cliff, flagged with a warning banner. Every output is cross-checked against an independent if/then formula so the methodology can be audited, not just trusted.

Default wattages and standalone monthly energy (at 30 days, before any slab effects). Use these as a starting point, then override the wattage to match your own appliance's nameplate.

The rupee cost of these units depends on your slab — that is exactly what the calculator above works out once you enter your baseline.

• PUCSL — Retail Tariff Determination (statutory regulator)
• Ceylon Electricity Board — Tariff Information
• LECO — Tariff schedule
• Sri Lanka Sustainable Energy Authority — appliance labelling (default wattages)

Block rates, fixed charges and the retroactive slab logic are reused from this site's unit-tested PUCSL — Retail Tariff Determination, March 2025 engine, last cross-checked on 2026-06-14. Default appliance wattages are typical nameplate ratings and can be overridden on every field.