A year of solar heating

The unseasonably good weather at Hillside over the past few days, with clear blue skies from dawn to dusk and temperatures around 25C, is a very pleasant suprise. Along with giving us a welcome last taste of summer that wasn't very forthcoming in July and August, it means we can eke some more use out of the solar hot water system.

2011 has been our first full year of using solar hot water. Whilst we'll get a few more good days from the unexpected sunshine, we've now had most of the useful sunshine for the year so now is a good time to review how the system has performed.

This year has seen us generate around 2,200 kwhs of hot water from the sun, and we expect it to reach 2,500 before the year is out. If we had used gas to generate the same amount of hot water it would have cost us approximately £92 on a typical tariff. However, we don't have gas in the village so would have to use either electricity, oil or wood pellets. The equivalent costs for these would be £315, £145 or £130 respectively. As wood pellets are our fuel source we'll use that in our calculations.

Our Navitron, self-installed, 30 tube solar thermal system cost just over £1,000 excluding the twin coil hot water cylinder which we bought separately. If you bought the complete kit from Navitron it'd set you back £1,600.

So, using the figures calculated above and the cost of the complete kit, a simple payback calculation shows the solar thermal system will pay for itself in 12 years. I must admit I'm slightly disappointed by this as I thought it'd be less. However, you could take the view that before the renovation project we would've been using oil, and we had to replace the cylinder anyway so the true payback is £1000/£145, and is a much more satisfying 6.9 years.

Even the 12 year payback period shows that the system will easily pay for itself in it's 20+ year lifetime. So we can rest in the knowledge that the solar thermal system is not only cutting our CO2 emissions, it's also saving us money in the long-term.