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Let there be light

Be prepared to tackle power outages this summer. Here are some back-up options that will ensure you are never in the dark.

Earth hour may have appeased our collective environmental conscience, but nobody follows the green diktat more religiously than the electricity department in summers. When the power to your home is cut off for the nth hour this season, don't lose your cool. Just be prepared. Here's how you can light up your lives without putting your finances in the dark.

The two most popular options for back-up power are inverters and generators. Your choice should depend on the number of appliances you want to run, the power they require and the duration for which you will need emergency power. A rough guide is to go for an inverter if the combined load of the appliances is about 1,000 W (lights, fans and a TV). If it is closer to 2,000 W (for air conditioner, refrigerator or a microwave oven), you can buy a generator. Inverters for higher loads are also available these days and, in fact, have an edge—not only is their running cost lower, they also provide pollutionand noise-free power.

Improve The Charge
For a longer battery life, do not use more than 50% of its rated capacity before recharging.
Check that the inverter or generator has overload protection, that is, it should switch off automatically when the load increases.
Keep the device on a flat surface and in a well-ventilated area protected from rain or moisture.
In case of an inverter, the battery will self-discharge. Make sure that it is not discharged below the desired level as this will reduce its life drastically.
If your area has low voltage, the inverter might not be charged properly, so you will have to buy an automatic voltage stabiliser.

Always pick a model with capacity that is higher than your estimated load value in order to avoid tripping if you switch on a heavier appliance by accident. The thumb rule is to add 20% to the heaviest load you have calculated. Also, some items have a higher start-up load and require more power to start than to run. To help you get through this first step, you can use load calculators that some companies have on their Websites.

When you buy an inverter, one of the first things the shopkeeper will ask you is whether you want a pure sine wave or a modified sine wave one. Don't be frazzled by the jargon. In layman terms, you should opt for a pure or true sine wave if you want to run sensitive equipment like a laptop, but for fans and TV, a modified sine wave is good enough — and also more affordable.

The most important part in an inverter is its battery. A suitable way of calculating the battery power is load/volt x back-up hours =Ampere hour. So if your load is 500 W and the electricity is going to be out for four hours, then the battery power should be 500/12 V x 4 =167 Ah. If you opt for lead acid batteries, you will have to check the level of distilled water and clean the terminals regularly. You can choose maintenance-free batteries, which are slightly more expensive. Most batteries have a shelf-life of about two years. An inverter as well as a battery will cost you upwards of Rs 4,000. It might be fruitful to check with local dealers as some rent an inverter for 6-12 months.

Options To Power Up
  Inverter (with battery) Generator Solar panel inverter (with battery)
Price Rs 12,000 Rs 35,000 Rs 27,000
Charging time 5-6 hrs Nil 6-8 hrs
Running cost Rs 50/4 hrs Rs 100/4 hrs N.A.
Appliances you can use Two CFLs, two fans and a TV Four CFLs, two fans, a TV and a refrigerator Two CFLs and a fan
Fuel Charged by electricity Starts on petrol, but runs on kerosene Sunlight (solar energy)
Annual maintenance cost Rs 100 for cleaning and re-filling distilled water Rs 500 for changing engine oil; Rs 300 for filters Rs 100 for cleaning and re-filling distilled water
Replacement time 2 years for batteries 6 months to 1 year for fuel and oil filters 3-4 years for batteries
Price can vary depending on the model. Running cost depends on the number and power of appliances.

Generators have a higher running cost as they consume expensive fuel. The most common ones use petrol to start with and kerosene to run or you can opt for one that uses only diesel. LPG generators are also available, though not so easily, and are costly. You don't have to worry too much about the noise as most generators have acoustic enclosures to comply with the Central Pollution Control Board norms. The starting price for a generator is Rs 10,000, with an 800 VA available for Rs 12,500, while a 1 KVA generator costs more than Rs 22,500. Check for the fuel gauge and oil alert option while buying a generator. The engine oil should be replaced after every 70-100 hours of use.

If you want a no-cost fuel, harness the power of solar energy, although the high initial cost is a deterrent. For instance, a 37 W solar panel costs about Rs 7,000, and for a solar inverter to be charged fully, you will need at least two such panels, if not more. A solar inverter is more expensive also because it comes with a charge controller. "A sensible option is to have a hybrid inverter, use a solar panel to keep the battery fully charged during the day and plug it to the main electrical supply at night," says Subodh Raheja, president, Manak Engineering Service.

In case of the hybrid option, you will also have to shell out extra for the battery, which is bound to stretch your budget. The benefit is that solar panels are easy to install, have a life of more than 30 years and incur an extremely low recurrent cost. You can opt for a simple home kit, which costs Rs 11,000 and consists of a 37 W panel, a 40 Ah battery, a 5 amp charge controller and two 9 W CFLs. So, go ahead, make power while the sun shines.