Two weeks ago I tweeted that I’d decided to switch off our mains hot water for the summer, to let our solar water heating come into its own. I don’t have many years of data, but this now annual household event – the big ‘switch-off’ – says a lot about our summer weather prospects. This year, it’s not looking good!

Two years ago I switched off our mains hot water very early, around March/April, then just made do with a few boosts of mains power to carry us right through until September. Last year our switch-off was in May, I think, and again we lasted until about September without much mains hot water.

When our solar hot water is on I’ve found I become quite the weather watcher. I’m always checking the next 3-5 days’ forecast to see whether I’ll need to boost the system. For example here’s a current forecast:

Photo: Weather forecast, courtesy of the BBC.
Photo: Weather forecast, courtesy of the BBC.

Experience has shown that more than a few days of cloudy/cold weather necessitates a boost. Patchy cloud and sun are generally OK though. Looking at this, I think the system will run without a boost. Having said that we haven’t had much sun over the past few days to build up much of a reserve of hot water in the tank. Our tolerance for tepid showers is going to be tested in other words! With a few days of 25-30C showers, the system should ‘limp’ on until the next sunny day(s). (Too much cloud cover, or if it gets too cold out, and the solar hot water remains offline to avoid pumping in water that’s colder than the probably already quite cool residual water in the hot water tank.)

It’s quite nice to feel a connection between the weather and the services and level of comfort I expect from my water uses. In fact I’ve been reading about this very topic, i.e. water practices and comfort expectations, in the past few days. I came across the recent Patterns of Water final report (March 2013) by the Sustainable Practices Research Group (SPRG). I’ll post up about it in detail very soon – particularly as its UK surveys show quite strikingly just how atypical I am as a ‘water user’ (compared to the survey sample at least). Turns out having things like solar hot water, a water butt, tap aerators and so forth is sadly very rare here in the UK…

Duncan Thomas

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