wrote in message
oups.com...
Mark wrote:
Ed Sirett wrote in message

If you'd payed a lot (£2,000 say) for the system then I have no doubt
you'd not recover the cost. What might be the threshhold?

That's still a moving target, how much
will energy prices have to increase
before we can't afford NOT to fit some
type of solar heating.

another good question, and another
bastion of solar DHW support. So,
lets find out:

At todays prices a £2000 commercial system saves in the region of £20
per annum on hot water bills. This is in the region of a tenth the
amount that woud be needed for the unit to eventually pay its install
cost.

To pay back £2000 @ 5% over x years would require a yearly payback of
- calculator time -

over 10 years: £254.52 per annum
over 15 years: £189.84 per annum
over 20 years: £158.40 per annum
over 25 years: £140.28 per annum
over 50 years: £117.6 per annum
over 100 years: £100.68 per annum
infinity years: £100 per annum.


Look at the 10 years figure. That doers not take into account that energy
may be twice as much in 10 years and has risen steadily along the way. The
payback calcs are more complex than this simplistic view.

That is having one installed commercially. DIYing the installation will
payback rather quicker. Also saving £20 per year in DHW bills is rather on
the conservative side. I know of a few solar systems that produce 2/3 to 3/4
of all DHW needs, and these must save far more than £20 per right now. If a
solar system is DIYed, is large covering most of the roof, or all of it, and
this energy gained is used to supplement heating too, then the matter may be
more beneficial again. Solar heating is more feasible in cold northerly
Scotland, as they have a heating season 9 months of the year, so any free
energy gained is a bonus at any time. And as free energy is being collected
for 9 months, more of it is being captured over the year. It all adds up.