Quick Facts
What HT and LT mean
HT and LT refer to the voltage level at which electricity is delivered from the DISCOM to the consumer. The two categories correspond to different infrastructure, tariff structures, and operational rules.
HT (High Tension): Voltages of 11 kV, 22 kV, or 33 kV at the consumer connection point. Used by large commercial and industrial consumers with significant load. The HT connection comes from the DISCOM’s HT feeder, with the step-down to LT happening at the consumer’s own transformer.
LT (Low Tension): Voltages of 230 V single-phase or 415 V three-phase at the consumer’s meter. Used by residential, small commercial, and small industrial consumers. The DISCOM has already stepped down from HT at a public distribution transformer; the LT consumer receives ready-to-use voltage.
EHT (Extra High Tension): Voltages of 33 kV and above (33, 66, 132, 220, 400 kV). Used by the largest industrial consumers and as the inter-state transmission level. EHT consumers have separate tariff treatment.
Tariff differences between HT and LT
HT tariffs are structured differently from LT tariffs.
LT residential: Tariffs typically Rs 4 to Rs 9 per kWh in tiered slabs (lower slabs cheaper for first 100 to 200 units). Fixed charges are nominal, Rs 50 to Rs 150 per kW of sanctioned load per month.
LT commercial: Tariffs typically Rs 7 to Rs 12 per kWh, single-slab. Fixed charges higher than residential.
LT industrial: Lower tariffs than commercial, Rs 6 to Rs 9 per kWh. Demand charges may apply for larger LT industrial.
HT commercial and industrial: Tariffs Rs 6 to Rs 9 per kWh (varies by state and category). Significant demand charges, Rs 250 to Rs 550 per kVA per month, based on contract demand.
The per-kWh tariff savings of HT are partly offset by higher demand charges. The net economics depend on the consumer’s load factor (ratio of average to peak demand).
When to choose HT or LT
For a residential consumer, the choice is automatic: LT.
For a small commercial consumer (load under 50 to 100 kW), LT is the default.
For larger commercial and industrial consumers (load 100 to 500 kW), the choice between LT and HT involves trade-offs:
LT pros: Simpler infrastructure, lower upfront cost, DISCOM owns the transformer.
LT cons: Higher per-kWh tariff, less flexible for large loads.
HT pros: Lower per-kWh tariff, suited to large loads, future expansion capacity.
HT cons: Substantial transformer and switchgear CAPEX (Rs 5 to Rs 50 lakh), higher demand charges, more complex O&M.
Larger consumers (load 500 kW and above) almost always move to HT for the per-kWh tariff savings.
HT solar net metering
For HT consumers, rooftop or campus solar with net metering requires more complex coordination.
Inverter output is LT (typically 415 V three-phase). A step-up transformer is needed to convert to HT voltage for synchronisation with the consumer’s HT side. The step-up transformer adds Rs 5 to Rs 20 lakh CAPEX and slight conversion losses (2% to 3%).
The DISCOM net-metering application for HT requires substation-level feasibility study, possibly affecting the consumer’s connection if solar capacity is large relative to substation capacity.
Some states cap HT solar net metering at lower percentages of contract demand than LT solar at sanctioned load. Verify the latest SERC order before sizing.
LT solar net metering
For LT consumers, solar net metering is more straightforward.
Inverter output matches the LT connection voltage (230 V single-phase or 415 V three-phase). No step-up transformer needed.
DISCOM feasibility is at the local distribution transformer level. Multiple LT consumers on the same transformer compete for distribution transformer’s solar absorption capacity.
LT net metering is widely available with standard processes. PM Surya Ghar primarily targets LT residential consumers.
HT solar plus battery for demand management
For HT consumers with high demand charges, solar plus battery storage offers strong economics:
Solar reduces energy consumption (kWh charge).
Battery shaves peak demand (kVA demand charge).
For a HT consumer paying Rs 350 per kVA per month on 500 kVA contract demand (Rs 1.75 lakh monthly), shaving 100 kVA through battery dispatch saves Rs 35,000 per month, or Rs 4.2 lakh per year. The battery investment of Rs 25 to Rs 40 lakh for 100 to 200 kWh battery system delivers attractive payback alongside solar’s energy savings.
Power factor and HT consumers
Power factor is the ratio of real power (kW) to apparent power (kVA). HT and large LT consumers must maintain power factor above defined thresholds (typically 0.95 or 0.90) or face penalty charges.
Poor power factor (induced by inductive loads such as motors and transformers) increases the kVA recorded for the same kW load, inflating demand charges.
Capacitor banks correct power factor and reduce kVA demand without changing actual energy consumption. Most HT industrial consumers install power factor correction as standard.
Solar inverters typically operate at near-unity power factor (close to 1.0). Solar generation does not directly correct power factor but does not worsen it.
Common mistakes regarding HT and LT
Treating per-kWh tariff alone as the comparison. Demand charges and load factor matter equally.
Forgetting that HT solar needs step-up transformer. The CAPEX surprise can be Rs 10 to Rs 30 lakh.
Sizing solar against connected load instead of contract demand for HT consumers.
Ignoring the substation capacity constraint when planning large HT solar. The feasibility may be denied even if contract demand allows.
Not optimising power factor. Poor PF inflates HT demand charges materially.
Best practices
For consumers near the 100 to 500 kW load range, evaluate LT versus HT economics carefully before commitment.
For HT consumers planning solar, plan for step-up transformer CAPEX from day one.
For HT consumers with high demand charges, evaluate solar plus battery as a combined intervention.
Install power factor correction to keep PF above 0.95 and reduce kVA demand.
Coordinate with the DISCOM early for HT solar applications. Substation-level approvals can take longer than LT net metering.
For new construction with anticipated large load, declare HT connection from the start rather than upgrading from LT later.
Standards and references
HT and LT classifications follow CEA Connectivity Regulations 2019, IS 732 (wiring rules), and state DISCOM tariff orders. Specific voltage thresholds and tariff structures vary by state.
Related glossary terms
Key takeaways
HT (High Tension) connections operate at 11 kV or above, used by large commercial and industrial consumers. LT (Low Tension) connections are at 230 V single-phase or 415 V three-phase, used by residential and small commercial consumers. HT consumers have lower per-kWh tariffs but pay significant demand charges based on contract demand. For solar, HT installations require step-up transformers and substation-level coordination, while LT installations are more straightforward. Choosing between HT and LT depends on the consumer’s load size, load factor, and total cost analysis including both energy and demand charges.