A pressurized system should really be referred to as a "closed-loop pressurized antifreeze solar thermal system" – the two-word version is much simpler and more common! Pressurized systems are the most flexible type of solar hot water installation and, consequently, are the most common worldwide.

These systems work well in most climates and have been around for long enough that the technology is sturdy and reliable. They can be built in sizes appropriate for virtually any location and make a great long-term investment for your home.

Pressurized systems are indirect, active systems: unless they're using a thermosiphon setup, they always have at least one pump and use a separate solar fluid to carry heat from the collectors to the domestic supply. The fluid is typically a mix of high-temperature propylene glycol and water , which is resistant to temperature extremes (both low and high), and which transfers the energy gathered from solar radiation to the hot water tank via a heat exchanger.

Pressurized systems work very well in both residential and commercial settings. Thanks to their popularity and the fact that most residential installations are a similar size, most manufacturers even offer kits to take the guesswork out of the planning phase. You'll still need to go through your planning process to ensure you select the right size for your needs (and, of course, we recommend you consult a professional for their input) but the kits make life a lot easier.

If you buy from a reputable manufacturer, using a kit can cut your installation costs and heartache significantly, as well as providing easy access to standard-sized parts for maintenance. The amount you save in opting for a standard setup, rather than doing everything bespoke, could knock years off your return on investment period.