Saving costs using Solar Water Heater
Thursday, November 13th, 2008
We all have been talking of solar energy and how it can be a boost to not only cutting down on energy costs but also ecologically rewarding.
We are family of six (soon to be seven as my son is getting married) and use of hot water for that early morning bath and in the kitchen during Delhi’s winters is a must. Traditionally we were dependent on electric water heaters. Installed in each batch room and a small one in the kitchen. Taken together these accounted for 8.5kW of electric load. Granted that this is not a constant load but still it was a huge power consumption item.
The thing is that with advent of thermostat the heaters were always left powered on and even the heat loss due to radiation/conduction losses was made up by auto switching of the thermostat. Consider this situation in light of the fact that in India generally house plumbing has never been an item of insulation. So these “losses” were not insignificant, though we had never quantified these.
Two years back, in order to reduce electricity consumption, we did our self energy audit. As a result first we switched to use of CFL’s and in the kitchen provided for “instant” water heater instead of storage water heater. The former is needs no justification and the latter did show some promising savings though at cost of no heated water whenever one of the frequent power cuts made its presence felt. So “instant” type heaters were not an option for bathroom. We had time and again considered solar heaters but had abandoned the idea as feedback was not good. Most of the users talked about the “collector” tubes getting corroded. Some talked of not enough warm water during cloudy days.
This year we have installed a solar water heater and for the moment the contraption is working very fine. I know it is still early and not freezing winters but look at the temperature it shows early morning on a hazy day. It is at 75 degree centigrade! With two hundred liter of water at that temperature we can easily have five hundred liters of warm water for all the bathing and kitchen needs.
The comparative electricity bills would be only tallied at end of winter season with last years bills but we can already see reduction in daily units consumed. Just a quick back of envelop calculation showed that daily electricty consumption for water heating was Rs60 (Rs1800 monthly) for three water heaters of 2kW each. This is now net saving!
The total investment has been Rs55000 (including taxes, delivery and installation) for the solar water heater. Plus Rs5000 for some miscellaneous re-plumbing and insulation of exposed pipes to further cut down on heat losses. So the ROI is 3.5% monthly or about 20% annually onisdering six months of hot water use.
So what changed our minds? Well four things really:
The first of these was the new design of solar water heater. The design now on offer has actually two circuits. One is the closed heat water circuit of tubes that run from collector to the water drum. Second is the use water circuit that is from the feed tank and outlet to plumbing. Since the heat water circuit is independent we can use de-mineralised water here and avoid salt/corrosion build up. The use water circuit is using metal pipes which can be changed when the become corroded. The hot water tank is insulated and just for those days where there is continuously overcast sky there is a built in electric heater that can be switched on (or set for automatic switching if tempature falls below a set point)
Second and third were really monetary in form of government incentives.
The second was in form of outright subsidy of Rs10000. Which was processed within a week of our purchasing the solar water heater and making the full payment. The vendor did all the work application processing work. Frankly I was quite surprised to receive the cheque within short time.
The third took form of a 80% bank loan at annual rate of just 2%. That is right just 2%, which is practically a free gift. That is annual interest of Rs720 on Rs36000 loan. (This is roughly 80% of initial cost less subsidy).
Forthly all this is topped by a rebate of Rs200 per month from the electric utility. So between savings of electricity bill and rebate my loan installment would be amply taken care.
Do not fret let me just run the total calculations for you once again.
Total cost : Rs55000
Loan amount : Rs36000
Savings:
Monthly interest : Rs60 (Anual interest Rs720)
Monthly rebate : Rs200
Monthly saving : Rs900 (Rs1800 per month annualised)
Payouts:
Monthly installment : Rs1000 (for 36 months)
So actually I end up saving Rs100 every month right away and this will keep going up as more and more of loan is repaid.
I am a winner in any case and so is the environment. Why not you?
