Solar Thermal – Appeal Review

06Sep10

Ding ding Round 2 !

Nearly a year ago I looked at solar thermal for hot water and could not justify spending money on this technology.  So it’s time for an appeal review armed with all this recent solar knowledge and experience.

Why do I want to do this ?

  • I like the idea of saving money, CO2, reducing energy usage
  • I would really like some diversity from gas/boiler
  • Maybe even drop boiler maintenance contract (further saving)

Why not to do it ?

  • Currently our hot water usage and efficiency is surprisingly very good
  • Teenage shower madness has been solved with an aerated shower head
  • Too much effort for too little financial return
  • Gas is still very cheap per kWh, furthermore the standing charge or daily fee makes it less attractive to save on gas.

When next to consider it ?

  • When the Russians ramp up gas prices
  • When the gas distribution network gets unreliable
  • When I get a new boiler (a long time away)
  • If the RHI Renewable Heat Incentive scheme made it more financially attractive (cannot see that happening now)

Measuring Hot water gas costs
As you may know I’m now logging gas usage with the Brultech ECM 1240

What would I have proposed to fit at this point in time ?

  • Something like the Navitron high efficiency double wall evacuated solar tube panels
  • A new unvented highly insulated twin coil tank with electric backup heater.  (Maybe a thermal store – budget dependant)
  • Reconfigure boiler from direct HW to system boiler

Budget ?

Well assuming no RHI payment it would be a DIY low-budget outing ~ £1500.  Sized to provide 70% of hot water from the solar collectors.  This represents a 20 year payback for my current situation.  Note, that for ‘normal’ family using more hot water than us I reckon 10 years and for those using electric heating it would then be a no-brainer 3 years.

Appeal rejected – case dismissed

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