On Tue, 8 Jan 2008 19:22:59 +0000 (UTC) someone who may be Ed Sirett
wrote this:-

It might /just/ be possible to make a cost effective solar assisted HW
system if /all/ the following are true.

1) You need to replace the HW cylinder.
2) You have the time and skills necessary to make and install
solar collectors.
3) You have the time and skills needed to make the control system.
4) You have access to the scrap raw materials needed to make system.
e.g. discarded CH pump, discarded CH radiators.

If, for the sake of argument, one takes the claims of the antis of
only a £40 saving in gas per year at face value, assume no fuel
price increases and ignore the (low) electricity cost then a
simplistic simple payback period calculation for the Navitron Budget
Solar Kit http://www.navitron.org.uk/pricelist.htm is about 22 years
(£800 plus £100 delivery, if one doesn't collect it).



--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54