Do 250 watt or 150 watt high pressure lamps pay back faster when an Alwar oil mill swaps them for T5 sets?

In the Bureau of Energy Efficiency (BEE) Alwar manual a 250 watt (W) lamp the manual labels HPSV (usually high pressure sodium vapour, our reading) swapped for T5 tubes saves rupees (Rs) 2,160 a year, and a 150 W lamp Rs 1,350, at 3,000 hours. The sets cost about the same, so the 250 W swap pays back first.

The two reports side by side

• The manual writes HPSV and in its text calls the lamps high pressure mercury vapor lamps; HPSV normally means sodium vapour (our reading).
• 250 W HPSV lamp to a set of four 24 W T5 tubes, 96 W in all. Printed saving 150 W: 0.150 kilowatt (kW) x 3,000 hours x Rs 4.8 = Rs 2,160 a lamp a year. Set price Rs 3,500 to 4,500. Cluster: 10,410 kilowatt hours (kWh), Rs 0.5 lakh, cost Rs 0.8 lakh, payback printed as 18 to 19 months.
• 150 W HPSV lamp to four 14 W tubes, 56 W in all. Saving 94 W: 0.094 kW x 3,000 x Rs 4.8 = Rs 1,354 a year, printed as Rs 1,350. Set price Rs 3,000 to 4,000. Cluster: 15,625 kWh, Rs 0.75 lakh, cost Rs 1.7 lakh, payback 27 months.
• The manual says some units use HPSV lamps for street lighting, and suggests changing them on failure.

Per lamp, the bigger lamp wins

• 250 W: Rs 3,500 to 4,500 / Rs 2,160 = 1.6 to 2.1 years, 19 to 25 months. The printed 18 to 19 months fits only the low price.
• 150 W: Rs 3,000 to 4,000 / Rs 1,350 = 2.2 to 3.0 years, 27 to 36 months. The printed 27 months again fits only the low price.
• The two sets are priced within Rs 500 of each other, but the 250 W swap saves 60% more a year (2,160 / 1,350 = 1.6).

A small slip, and lamp counts

• 250 W minus 96 W is 154 W, not the 150 W printed. At 154 W the saving is Rs 2,218 a lamp.
• 10,410 kWh at 450 kWh a lamp is about 23 lamps. 23 sets at Rs 3,500 cost Rs 0.80 lakh, which ties to the printed cost.
• 15,625 kWh at 282 kWh a lamp is about 55 lamps. 55 sets at Rs 3,000 cost Rs 1.65 lakh, which ties to the printed Rs 1.7 lakh.
• The printed cluster rows fit the cheapest set price and about 78 lamps in all (our arithmetic; the manual prints no lamp count).

Before you swap

• The manual prints no lux figures for the sets. Measure the light at the pole or yard before and after.
• Our note, not the manual's: a lamp lit 4,000 hours a year instead of 3,000 saves a third more than the figures above.

The 250 W lamp worked through

• HPSV 250 W against four 24 W tubes at 96 W: printed saving 150 W
• 0.150 kW x 3,000 hours = 450 kWh, x Rs 4.8 = Rs 2,160 a year
• Payback at Rs 3,500: 1.6 years. At Rs 4,500: 2.1 years
• Carbon dioxide (CO2) at 0.675 kg a kWh, the financial year 2025-26 grid factor: 450 x 0.675 = 304 kg a lamp a year. The 150 W lamp: 282 x 0.675 = 190 kg
• Both cluster rows: 10,410 + 15,625 = 26,035 kWh x 0.675 = 17,574 kg, about 17.6 tonnes

Watts, hours, tariff and set prices are the manual's, at its date.

What Senseible does here

Senseible reads fuel invoices and electricity bills into monthly records, so last year's monthly kWh from your bills is on file to set against the year after a swap. It does not split out lighting, count lamps or measure lux. A lighting sub-meter is custom, on request.

• Alwar T5 tube report for 40 watt tubes
• Bulb and halogen swaps in an Alwar mill
• Do the Alwar manual totals add up
• Carbon calculators

Sources: Bureau of Energy Efficiency and Confederation of Indian Industry, Manual on energy conservation measures in the Alwar oil mill cluster (SAMEEEKSHA), Central Electricity Authority, CO2 Baseline Database for the Indian Power Sector (grid factor 0.675 kg CO2 per kWh, financial year 2025-26)

Last reviewed 2026-11-06. Figures are the manual's, from the Bureau of Energy Efficiency Small and Medium Enterprises (SME) programme, at its tariff and set prices. Get a current quote and check your hours before you rely on a payback.