African energy
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savings on the home ’ s electricity bills . Contradictions ? Misleading information ? Or selling on blind faith , hopes , and promises ?
Add into the equation that solar water heaters are perceived as being expensive , so the result is a sale of a 150l solar system ( because it is cheaper ). In most instances , a 300l-sized system is needed for a home of three to six people , based on a relatively conservative 75l of geyser hot water per person .
Typically , a 150l solar water heater saves around five kilowatt-hours ( kWh ) per day ( 60 % efficient ), and the home ’ s water heating is running at 15.35kWh . Put another way , the solar system is saving 30 % of the water-heating bill , and this , as a percentage of the home ’ s electricity bill , is only about 10 %. ( Eskom a few years ago calculated typical savings at 8 %.)
Little wonder that the consumer is disappointed . The outcome is not only a shoddy reputation for solar thermal in general , but those that went solar and were disappointed are putting off potential adopters .
However , if the solar supplier were to identify that the system being chosen would save a percentage of the hot water heating bill ( or more specifically , the electricity used in heating that volume of water ) then the false expectations would be overcome .
Each solar water heater could then stand on its own merits . Payback on investment and investment savings may all still be very attractive , and with the increasing price of electricity , most will achieve payback in three to five years — some considerably less .
Not surprisingly , few homes have any real idea of how much electricity they use in heating water and it is generally far more than they would expect .
A simple home audit is to read the electricity meter on three consecutive days at the same time ( 20:00 is a good time ), calculate the total kilowatt-hour consumption for the home , and average the daily consumption . Then turn off the geyser for 24 hours — at the same time — and back on again the next day , and calculate the consumption . Compare the two calculations and you will have an estimate of geyser electricity consumption . The only niggle with this is that the home will be out of hot water for most of the day .
With this basic approach , the plumber or consumer can easily determine what size of solar geyser they need or , more importantly , they can determine what amount of electricity they want to save through solar .
Choose a solar system based on financial arguments : solar savings in kilowatt-hours , cost per kilowatt-hour , and daily and monthly rand savings .
It is no different to buying a car . If you want performance , buy one model of car ; if you want fuel efficiency , buy another model .
It is not that solar water heaters are rubbish ; it is that neither the consumer nor the plumber is looking at the opportunity realistically . Solar thermal can and should be one of the best investments a home can make . PA
James Green is the CEO of Ubersolar and Pay As You Go Solar , and a member of the SESSA Council .