"A choice between solar water heater and geyser is like choosing between an aluminium utensil and pressure cooker. Pressure cookers save fuel and money, but the initial investment is much higher than that for aluminium pots," says Rajendra Bahadur Adhikary of the Centre for Renewable Energy. Sure, an electric geyser is cheaper, but it takes an hour to heat enough water for about one-and-a-half people running on some of the most expensive electricity in the world. Studies show that the pay-back time for investment in a solar water-heater is four to five years. But factoring in the benefits of "green" warm water throughout the day and the frequent hikes in electricity and fossil-fuel prices, the actual time-frame is shorter.

There are neither laws nor monitoring agencies to regulate the industry, and manufacturers have been known to be economical with the facts. So you need to arm yourself with important information before you have a solar water-heater installed to get a better bargain and to ensure the creature actually works.

The Valley is well-situated for the use of solar water-heaters, as it has 280-290 sunny days annually. A 200 litre water-heater costs Rs16-35,000 depending on the kinds and thickness of metal-sheets, pipes and insulators used. For a family of four, a water-heater with a 200 to 300 litre-capacity is sufficient.

About 100 of Nepal's 120 solar water-heater manufacturers are in the Kathmandu Valley. Solar water-heaters are pretty low-tech and your neighbourhood metal worker might now be putting his welding and wiring skills to manufacturing them. "The technology is easily adaptable and needs no formal training, and the business doesn't require a huge investment-anyone can turn entrepreneur," says Tri Ratna Bajracharya, renewable energy expert with the Institute of Engineering in Pulchowk. A really cheap deal in this case probably means you'll be hit with various hidden costs in the future-inefficiency, frequent servicing and repairs.

Solar water-heaters for domestic use are low-temperature devices that heat water up to 65 degrees. The average efficiency is 30 percent-not terribly high, and it depends on the materials used to make the collectors, coils and insulators. Copper sheets and pipes, and good insulators like glass-wool and thermocole, can push efficiency up to 40 percent, while aluminium sheets and GI pipe can lower it to 20 percent. A 200 litre heater using light or medium GI pipe with aluminium sheets for collectors and cloth or sawdust as insulation, costs Rs16-18,000. It's cheap, but may be of no use in the winter.

The same size heater with heavy-gauge aluminium sheets and Nepal Standard-certified pies, costs Rs24,000, while a 300 litre heater similarly high quality is Rs26-35,000. A really superior 300 litre heater with three or four standard collectors or two double collectors measuring six square metres costs between Rs35-50,000. Potential buyers also need to look into the size of the collectors: standard ones are 1x1.5 m. For comfortably warm water on foggy December and January days, an electric booster helps. Some manufacturers supply boosters as part of the package, others charge an additional Rs2,500. It depends on how well you bargain. The same goes for installation and delivery in the Valley. Slick Australian solar water-heaters are also available at ATC Private Limited, which says it fulfils order within a week. They cost a fortune, though. A two panel 300 litre water heater costs well above Rs100,000, while a three panel heater of the same capacity is Rs200,000. They're also available in 125 litre and 440 litres capacities.

The government doesn't offer subsidies or other incentives like soft loans or tax breaks to solar water-heater fabricators and users because, according to the Alternative Energy Promotion Centre at the Science and Technology Ministry, it's against government policy to subsidise commercial-scale industries. Even finance companies don't offer hire-purchase or deferred payment schemes. Import tax is levied on all solar water-heater parts, but manufacturers claim they still sell at low margins. The only real break consumers get is no VAT, part of the government's attempt to promote renewable energy use. What you can do is buy a large capacity heater initially and add new panels later. This does cost more than if you pay for the whole thing at one go.

Good companies give you an 8 to 10 year guarantee against manufacturing defects. Keeping the panels clean, maintaining the black paint and rubber shields, and flushing the heater every two years is enough. Manufactures provide servicing facilities to their clients, but are of little help if your plumbing is defective. Consulting a solar water-heater manufacturer or ensuring your architect plans for installation of a solar powered water-heater is important.