LT vs HT Connection for a Factory: Tariff, Works and When to Switch

A factory moves from LT to HT when its contract demand crosses the ceiling in the state supply code for 415 V supply. In Punjab, industrial demand up to 100 kVA is specified at 400 V, and 11 kV is specified above that up to 4,000 kVA. HT brings a consumer-owned substation, inspectorate approval and a different tariff in return for capacity to grow. Other states use other cut-offs.

How do LT and HT supply compare?

Our LT versus HT glossary entry and the longer article on LT versus HT power distribution in industrial plants go into the engineering behind this table.

What decides which voltage you are given?

The state supply code decides, in terms of contract demand or load. The Punjab Supply Code, up to its 11th amendment, lists three-phase 400 V for industrial demand not exceeding 100 kVA, three-phase 11 kV for large supply consumers with contract demand up to 4,000 kVA, and 33/66 kV above that up to 20 MVA. Other states define thresholds in kW or kVA at other values, so do not carry the Punjab figures across a border.

Two provisions in that code are worth knowing wherever you are. The licensee may release supply at a lower voltage than the one specified if there is a constraint, subject to a surcharge in the General Conditions of Tariff. In 2016 the Commission's order set a 15 percent surcharge on consumers supplied at 400 V against a specified 11 kV; check the current tariff order for the rate in force. And a consumer may opt for a higher voltage than the one specified, which the licensee may grant if technically feasible. Both are useful when you sit near a threshold.

How does the tariff differ?

Tariff orders differ by state and year, so we do not quote rates. The pattern to check is the same. HT tariffs commonly bill a demand charge on contract demand in kVA in addition to energy charges, and they may carry a rebate for taking supply at a higher voltage; Punjab's code states that a consumer is entitled to a voltage rebate approved in the tariff order for the year against the voltage at which the load is catered. LT industrial tariffs are simpler. What matters is your own numbers: load factor, power factor, contract demand against actual maximum demand, and the energy charge difference. Put last year's bills through both tariff schedules, then add the annual cost of owning the substation.

What works does HT need?

HT turns your incomer into a small substation. The works usually include an HT service connection from the DISCOM's 11 kV line, an HT metering cubicle, an HT breaker panel with protection, one or more transformers, LT incomer panels, earthing and a lightning arrester, cable trenches and a transformer plinth with fire separation and oil drainage. Size the transformer from the connected load, diversity and growth with the transformer sizing calculator and cross-check the demand with the factory electrical capacity calculator. Our page on HT and LT distribution and substations lists what the scope covers.

Approvals add time. In most states drawings and inspection by the Electrical Inspector come before energisation; our guide to CEIG approval for factories sets out the sequence. States differ here too: an Energy Department notification in Odisha, uploaded in June 2026, provides that installations up to 33 kV are self-certified by the owner through certified chartered electrical safety engineers, while installations under section 54 of the Electricity Act, and mines, oil fields and railways, stay with the Electrical Inspector. Confirm your own state's position before you plan.

What does the changeover look like on site?

A new substation is built beside the running LT supply, so the factory keeps producing while the work proceeds. The disruption sits in the cut-over. Plan it as a scheduled shutdown with a written sequence and a rollback: keep the existing LT supply available until the HT side has passed inspection and the DISCOM has changed the metering; re-test the DG changeover interlock so the generator can never back-feed the new transformer; and record earth resistance for every pit before the inspector arrives. Choose a low-load window, tell the DISCOM in advance and have the contractor's protection engineer on site for the first energisation. A switch done in this order costs a planned stoppage; a switch done in a hurry costs a faulty trip on the first morning.

When should you switch?

1. The load will cross the code's LT ceiling. Then the question is when, not whether. Apply early, because transformer lead time and approvals set the schedule.
2. You are close to the ceiling and growing. Compare the HT tariff plus the voltage rebate against the capital and upkeep of a substation. If expansion is planned within a few years, building the substation once, with a transformer bay for growth, usually costs less than two staged upgrades.
3. Power quality or reliability matters. Heavy motors, drives and sensitive process loads can justify an HT connection and your own transformer, subject to what the DISCOM's feeder can give.
4. You plan solar or open access. Metering and the point of connection change at HT, so settle how the plant will be metered before you freeze the single-line diagram. Our contract demand entry explains the billing figure.
5. You are comfortable owning the assets. If a licensed contractor will not be maintaining the substation, plan the maintenance contract at the outset.

If none of these applies, stay LT and review again when the load plan changes. Our note on HT connection delays in north India describes where schedules slip.

How Secured Engineers helps

We design HT and LT electrical infrastructure in-house, and file the CEIG drawings and inspection and the DISCOM paperwork in-house. Electrical, fire, HVAC and solar work can sit under one contract. We work from offices in Noida (Delhi NCR) and Ludhiana, with 535+ projects across 18+ states and 89.77% repeat clients.

If you hold a recent bill, a load list and a site plan, send them and we will say which side of your state's threshold you sit on and what a switch would involve. Start from our electrical infrastructure page, message us on WhatsApp, call +91 70099 85817, or ask for a free proposal.