No matter how you do the economics, the best time to install any solar hot water system is 5 years ago. Given that this is not usually possible, any time from then up to the present day- and even a little bit into the future- is a good second best.
Every household uses different amounts of hot water. How much you will save on your electricity bill by using solar hot water heating will depend on how you use the system, the size of your system, and where you live. As a rule of thumb, you can expect to save up to 75% of your hot water bill by using solar energy.
The financial rate of return is not so easy to calculate- are you comparing the money spent on a solar system to money invested in a bank account? …off a mortgage? …and for how long? You had better include your marginal tax rate in the equation too! All have different interest rates and will give different rates of return. As a general rule, with a return of close to 12% tax free in perpetuity, solar hot water heating is hard to beat. We calculate that a Thermocell solar system has a payback of around 8 years. After that, your summer hot water is free, as is a considerable amount of your winter hot water.
A particularily good time to install solar is when the building is under construction. Installation costs can be kept to a minimum by plumbing and wiring the system before the wall coverings are put up. By designing the house to accommodate a solar system, optimum performance can usually be arranged at little or no effort.
If the building owner cannot afford to install solar heating immediately, it may be sensible to install a solar hot water cylinder and plumbing at the construction stage to make provision for a future solar system.
The major advantage of installing solar heating in new buildings is that overall savings in the cost of installation can be achieved by integrating the solar panels as part of the roof structure. This is easliy achieved using our in-roof system where the absorbers effectively fit in underneath standard skylight fittings. If you are going to the effort of building a house, we recommend that the design stage is also the best time to look carefully at optimising the building’s overall energy efficiency.
It is straightforward to install an on-roof Thermocell solar system into most homes at any time. While your existing hot water cylinder will work just fine, changing it out for a purpose-built Thermocell Sunstore solar hot water cylinder will provide the ultimate in performance. It makes sense to replace your existing hot water cylinder if it was manufactured before 1988 when a much improved hot water cylinder insulation standard was introduced.