It's a no-brainer, but you'd be surprised how many people do not sit down and plan every aspect of their solar thermal installation before they go out and buy materials. Installing a solar thermal system is a huge project with far-reaching ramifications for your home: the equipment will be in place for decades, so you need to get it right or spend years messing around with expensive repairs and adjustments.

Professional installers make it look easy, of course. That's their job. They have the experience to look over a site and immediately cross off inappropriate options, reducing the number of choices to those which will work for your needs, your location and your site. They look at an enormous range of important features, but here's a short-list to show you the sort of thing they consider:

• Load analysis: the load your home can carry on the roof, or wherever you will site your collector array, determines the size of the collectors.
• Solar window : the best location for your collector array depends on the solar window and any obstructions.
• Building layout: combined with the collector location, this determines where the pipes will go and how they will carry solar fluid from the collectors.
• Water tank: an existing tank usually defines where the solar tank and heat exchanger will be sited.

These are just a few of the most basic decisions to take before you even begin thinking about components, costs, labor and everything else. And the worst thing is that getting them wrong will affect every aspect of your installation, potentially for years to come.

Take some good advice: allow plenty of time to plan your solar thermal installation. Don't rush into it because you're enthusiastic and motivated – use that energy to plan carefully, to take measurements, to talk to professionals and to seriously consider the best options for your needs.