How much does solar thermal really save?
Posted by Helena Ripley on 21 September 2015 at 11:55 am
Solar thermal panels providing hot water for your domestic needs are a good way of reducing both your carbon emissions and your energy bill. Some households can use solar thermal to provide all of their hot water needs throughout the summer months. One SuperHomer manages to solely use solar heated water from March to November! But how much can they actually save?
This is a really difficult question to answer! It depends primarily on three things: price, energy and usage. The price of a solar thermal installation varies hugely, with estimates from £3000 to £6000. As this depends on the type of panels you choose, which installer you go for, and the state of your boiler, plumbing and roof, it is impossible to calculate a universal average cost. The amount of energy a solar thermal system will save you depends on the slope and direction of your roof, because these determine how much solar radiation hits your panels. And the monetary savings depend on how much hot water you use, what you use it for and when, and the fuel you'd normally use to heat it.
We’ve calculated, based on figures from the Department of Energy and Climate Change, that solar thermal could in most cases save you something in the region of £75. This assumes that solar panels will save on average 10% from your energy bill when you exclude electricity. To make the most of your solar heated water (and save the most money) you may have to make a few changes to your lifestyle: using a shower rather than a bath, and doing so in the evening instead of the morning. Other useful changes include using pre-heated water in your washing machine and dishwasher and using your boiler as a boost only after the sun has set.
The renewable heat incentive (RHI) is also available for solar thermal and is one of the few government subsidies that they don’t seem to be cutting at the moment. The amount you can earn through RHI depends on how much energy your solar thermal panels generate; the current tariff is 19.51p/kWh. The RHI is available for seven years, which is much shorter than the feed-in tariff, but it seems to be the right length of time to pay off your solar thermal system.
Let’s do the maths. A recent correspondent explained that their system would generate 1,800 kWh and was going to cost £4,200. They calculated that a 10% decrease on their energy bill would save £100.80 per year. The income through RHI would be £351.18. That means that their system would not have paid back within the seven years. However, there is another consideration: increasing gas prices. Between 2004 and 2014 gas prices rose by some 115%. Imagine what your gas bill will look like in 2025! Solar thermal systems last about 20 years and will probably be saving you more money every year. Electricity prices are going up by similar amounts so if you currently heat your water electrically the savings from switching to solar thermal are even greater.
A solar thermal system is an investment. The RHI can support its installation now and savings will be made for many years to come. There is very little maintenance required, so ongoing costs are minimal.
Photo credit: SuperHomes
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