Untrue headlines, fictional news and false facts. Conspiracy theories are reaching new heights across the world, the UK (Brexit), in the USA (Trump) and of course in South Africa.
Having got your attention, unfortunately there is a certain amount of truth in the statement ‘solar water heating is crap’, as many consumers and indeed plumbers think exactly that.
The problem is not that they are crap but misinformation, lack of understanding and unrealistic expectations. While the Department of Energy states ‘Water-heating accounts for a third to half of the energy consumption in the average household’, and Eskom ‘An electrical element geyser (will use) up to 40% of the average household's energy costs’, solar water heater suppliers have claimed savings of up to 40%-60% of the home’s monthly electricity bill.
Well maybe, but only if the solar water heater is sized correctly and the power output matches the kWh being used heating water. In 90%+ of cases this has not happened.
Studying the output of solar water heaters reveals that most solar systems are only about 70% efficient in replacing the electricity normally used in heating the tanks volume. Amazingly power output in kWh on solar thermal systems is almost never mentioned on information sheets and websites.
At the same time, ‘savings calculators’ through (solar water heaters) on home electricity bills suggest anywhere between 35% and 45% 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, and the result is a sale of a 150l solar system (because it is cheaper). In most cases a 300l sized system is needed for a home of 3 to 6 people, based on a relatively conservative 75 litres of geyser hot water per person.
The end result is typically a solar water heater of 150l that is saving around 5 kWh per day (60% efficient) and the homes water heating is running at 15,35 kWh. Put another way the solar system is saving 30% of the water heating bill, and this as a percentage of the homes electricity bill is only about 10%. (Eskom a few years back calculated typical savings at 8%).
Little wonder that the consumer is disappointed. The result is not only a shit reputation for solar thermal in general, but potential adopters being put off by those that have gone solar and been disappointed.
However, if the solar supplier identified 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, the false expectations would be overcome.
Each solar water heater can then stand on its own merits. Payback on investment, investment savings, may all still be very attractive and with the increasing price of electricity most will achieve payback in 3 to 5 years, and some considerably less.
Not surprisingly few homes have any real idea of how much electricity they use heating water and it is generally far more than they would expect.
A simple home audit is to read the electricity meter on 3 consecutive days at the same time, 8pm is a good time, and calculate the total kWh consumption for the home. 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 and you have an estimate of geyser electricity consumption. The only problem with this is that the home will be out of hot water for much of the day.
With this basic approach the plumber or consumer can easily determine what size of solar geyser, or more importantly the amount of electricity they want to save through solar.
Choose the solar system based on financial arguments, solar savings in kWh, cost per kWh, savings daily in Rands, monthly Rand savings, and do the maths.
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 crap, it is that neither the consumer (or plumber) is looking at the opportunity realistically. Solar thermal can, and should, be one of the best investments a home can make.
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