Time-of-Use vs General tariff: which is cheaper for your site?

Why isn't Time-of-Use automatically cheaper?

Time-of-Use rewards an appropriate load shape, not merely a business that stays open overnight.

Its off-peak energy rate is lower than General, but its peak energy rate is higher, and its combined peak-period demand rate is also higher per

kilowatt. A site can benefit on energy while losing more on demand. Comparing only the off-peak headline rate hides that trade-off.

Keep the scope clear: the formulas below use the non-domestic medium-voltage schedule effective 1 July 2025.

Low-voltage, high-voltage and special-category accounts need different rates and eligibility checks.

Before applying for a switch, confirm the tariff category, metering arrangement and any contract requirements with TNB.

A spreadsheet result does not itself establish that your account can change tariff.

What is the off-peak energy break-even formula?

Let s be the share of total kWh consumed off-peak, expressed between zero and one.

The weighted Time-of-Use energy rate is peak rate multiplied by the peak share, plus off-peak rate multiplied by the off-peak share.

Equate that weighted rate to the General energy price to find the threshold. This calculation considers the base energy component only.

Formula: s = (31.32 − 29.83) / (31.32 − 27.23) = 36.43%. Above this off-peak energy share, the Time-of-Use base energy component is cheaper;

below it, General is cheaper on energy. The shorthand 'about 36%' is rounded. Use the full rates, not the rounded shorthand, when repricing actual bills.

What is the peak-demand break-even formula?

Let D be the maximum demand measured across the billing month and P the maximum demand within that month's Time-of-Use peak periods.

The General capacity-plus-network cost is RM89.27 multiplied by D; the Time-of-Use equivalent is RM97.06 multiplied by P. These maxima may occur in different half-hours.

Do not substitute average demand for either value.

Formula: P / D = (29.43 + 59.84) / (30.19 + 66.87) = 91.97%.

Time-of-Use is cheaper on these demand components when peak-period demand is below this share of all-hours demand.

'About 92%' is a rounded summary, not a promise that a site meeting it will have the lowest complete bill.

How do I combine energy and demand correctly?

For each bill, separate peak kWh, off-peak kWh, all-hours maximum demand and peak-period maximum demand.

Apply each eligible tariff to exactly those same measurements, then add its applicable retail and adjustment components.

Compare the total difference in ringgit across the year. A percentage energy threshold and a percentage demand threshold cannot simply be averaged together.

Formula: base ToU − base General = kWh × ([31.32 × (1 − s) + 27.23 × s − 29.83] / 100) + 97.06 ×

P − 89.27 × D. The /100 converts sen to ringgit. Equal retail charges cancel in this particular comparison;

any unequal or account-specific components must still be included.

Which half-hours count as peak or off-peak?

TNB publishes the peak window as 2pm–10pm Monday to Friday, with off-peak periods outside that window, throughout weekends and on the specified public holidays.

Calculate the off-peak share from energy consumed in those intervals.

Counting how many hours are off-peak is not equivalent: a site might use almost all its energy in the shorter peak window.

Check whether the export timestamp marks the start or end of an interval. Boundary classification at 2pm and 10pm changes if that convention is misunderstood.

Use local Malaysian time, the relevant holiday calendar and the bill's exact start and end dates.

Missing or duplicated records should be reconciled rather than silently filled with averages.

Why do seasonal and irregular sites need a full year?

A warehouse, factory or cold store can have very different loading, production and refrigeration patterns through the year.

A shutdown month may show an attractive off-peak share while a busy month sets high peak-period demand. Monthly demand charges also reset by billing period;

the largest peak of the year is not automatically billed at that same value in every month.

Compare annual totals and show the monthly result as well. This exposes a switch that works overall but increases costs in certain periods.

Keep the comparison distinct from a proposed operational change: first reprice the existing load, then model an achievable revised load.

Mixing the two can make a tariff recommendation appear to deliver an operational saving it did not create.

What should I do before changing tariff?

Ask for an auditable comparison showing the published rates, eligible tariff categories, peak calendar, interval reconciliation and the demand interval for every month.

Check the assumptions about future operations and obtain TNB's current change requirements.

Keep a record of the approved switch date so that the first new bill can be reconciled against the correct schedule and period.

Rukan can review the available bills and half-hourly export without assuming Time-of-Use is the answer.

We show whether the opportunity comes from tariff fit, demand timing, power factor or billing accuracy. Upload your bills from the homepage to begin;

if you do not have the interval file, bills alone are enough for an initial review.