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.


So, even if all such systems lasted the entire life of the universe
with never a need for repair, the £2000 spend would be almost entirely
lost. In no sense are these systems an investment, whether short term,
medium term, long term, or even infinite term.


Lastly, how much do energy prices need to rise to make these pay their
way? Well, if an infinite amount of time to pay off their cost is
acceptable, and there is zero risk of ever needing repair or
decommissioning, then current energy prices would need to rise to
roughly around 5x the present price. Since there are already various
renewable energy technologies up and running, with huge implementation
capacity available, at a fraction of 5x current oil based costs, this
paying-their-way scenario will never happen. They can never pay off
their cost, not even applying the most extreme and unrealistic
optimism.

The lie is dead.


NT