You need not pay your power bill. Here’s how

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NEW DELHI: How would you like not paying your electricity bill at all? That’s possible. No, it’s not about an election-time promise by a political party. It’s about the new technology which is now commercially available — the solar power. It’s environment friendly as well as cost effective. It can cut your electricity bill by at least 90 per cent. All you need is access to rooftop.

We explain how a family of four living in Delhi in a 2 BHK, 900 square feet home with access to a rooftop can benefit by switching to a rooftop solar-power system.

This family uses a refrigerator, a washing machine, a hot-water geyser, a television set, two air-conditioners, five-six tube lights and a few electrical appliances in the kitchen. In all, it has 20-25 appliances ranging from a mobile phone charger to an AC.


Here’s a break-up of all the energy these devices would use on an average and the cost of running them per day:

Appliances

Number of appliances

Energy intake (watt)
Hours used per day
Power use per day in kWh (1 kWh = 1 unit)
Television15060.300
Air-conditioner 1.5 ton23600518
Refrigerator1105242.52
Washing machine120020.400
25L water geysers1200012
Microwave oven170010.700
Laptop210060.600
Mobile phone chargers525180.45
Ceiling fans6450125.4
Sandwich maker170010.7

(When there is more than one appliance of the same type, the energy and cost of use is of the total number of appliances.)



Adding up the daily power consumption of all the appliance, we get 31.07 kWh units of electricity used per day and 932 units per month.

Delhi households using less than 200 units per month are charged Rs 3/kWh for energy consumption. If the usage exceeds 200 but is less than 400, the charge levied is Rs. 4.50/kWh. Between 401 units and 800 units the cost of electricity per unit is Rs 6.50. Above 800 but less than 1,200 units the cost of electricity is Rs 7/kWh and above 1,200 units, households are charged Rs 8/kWh.

According to the charges levied by the state, the total bill, of the above-mentioned family living in a 2BHK would be around Rs 6,500 a month. The figure has been deduced on the basis of electricity cost in Delhi, taking the daily usage of the appliances and factoring in how often they are used in a household.

According to Pranesh Chaudhary, founder and CEO of ZunRoof, a leading company among the solar power system manufacturers, switching to various solar power options can help reduce electricity bills by a staggering 92%. “A family which is getting an electricity bill upwards of Rs 6,000 would require a 5KW grid-tied or on-grid rooftop solar system, which will take around 500 sq ft. area of your roof, which can be optimised with good engineering design.” Sachin Bhalla, senior VP, marketing, Luminous power technologies, too says that in order to completely remove the electricity bill of up to Rs 5,000 to Rs 6,000, you will need a 5 kW on-grid system.

This family has two options: to go totally off grid or stay on the grid but use as much solar power as required and feed the remaining back into the grid.

OFF-GRID SYSTEM
Tell people you plan to live off-grid right in Delhi, and they won’t believe you. They would think you plan to live without electricity. Going off-grid means getting totally cut off from your regular power supply. However, with easy commercial availability of roof-top solar systems. you can actually go off-grid and depend solely on solar power generate don your rooftop.


An off-grid system stores in batteries the electricity produced using solar panels after conversion and utilises the stored energy by converting it back to AC.

However, an off-grid solar power system will be a little costlier than on-grid system because one has to have larger capacity to meet peak demand which is met through the grid in case of on-grid system.

For example, if you currently spend Rs 6,000 on monthly electricity, a 5KW system will cut your bill by at least 90 per cent. However, if you are going off-grid, you would need a bigger system so that it reduces your total bill to zero and can meet the peak demand (sometimes you will need more electricity than usual) by storing extra electricity.

You would need at least a 10kW system which would cost you around Rs 10 lakh and an extra Rs 1-2 lakh every three to five years on battery replacements. So, an off-grid system could cost more than twice as much as an on-grid system.

Bhalla advises against using an off-grid system in cities without long and frequent power cuts. “When you get an off-grid rooftop solar power system installed you prepare yourself for peak demand, generating and storing a lot of electricity. Now if you are not living in a place where power cuts are common, switching to off-grid is not something that we recommend.”

Using an off-grid system will bring you benefits only in the long run. Experts say that an off-grid system gives you financial benefits only after 10 years after installation. And, if your demand does not peak (that is cross your usual power consumption limit) too often, the extra electricity generated gets wasted.

ON-GRID SYSTEM
According to both Bhalla and Chaudhary, a more reliable and cost-effective way to use rooftop solar power is through an on-grid system. This system is developed to be used with the main supply line of electricity. Electricity generated using solar panels is fed back to the main grid in such a system. It uses a net meter, which monitors the usage of electricity and keeps track of the units fed back into the grid. The 2BHK house mentioned above would require a 5KW system. It will generate enough electricity to help save at least 90 per cent of the Rs 6,500 electricity bill. The rest of the electricity will be used from the main grid.


However, one downside is that an on-grid system does not work when the grid is down.

According to Chaudhary, an on-grid system is the best way forward when going solar. “An on-grid system would cost you around Rs 2-3 lakh with government provided subsidy, which until recently in Delhi was Rs 15,000 per kW. This system requires no storage so the initial cost is low and there is hardly any maintenance cost as it is tied to the grid.”

WHERE TO BUY
A number of companies sell rooftop solar-power systems, both on-grid and off-grid. These systems come with a 25-year performance warranty. Bhalla of Luminous says that a solar-power system is a long-term investment which recovers the cost in a few years. Here’s a list of a few of the companies offering these systems:

CompanyServices
On grid
Off grid
Solar by LuminosSite evaluation, savings calculation, financing, state-of-the art engineering and end-to-end solutions (including govt. approvals)YesYes
ZunRoof
Site evaluation, customised rooftop design, lifetime support.YesYes
TATA Power Solar
Energy tracker, round-the-clock customer support, 25-year-warranty and saving calculator.YesYes







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