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, Decision on Electricity Tariffs, May 2026 is retroactive. Your total monthly units pick one of three consumption bands, 0–60, above 60 up to 180, and above 180, and then every unit is charged on that band's rate ladder, not just the units above the previous ceiling. A fixed charge is added on top, stepping at 30, 60, 90, 120 and 180 units. 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 and the retroactive repricing of your existing units if the extra load pushes you into a higher band. 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 nothing steps the two figures match; when a fixed-charge step or a band boundary is crossed the gap is the 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 band 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, Decision on Electricity Tariffs, May 2026 engine, last cross-checked on 2026-09-23. Default appliance wattages are typical nameplate ratings and can be overridden on every field.