sorry to hijack the thread, but it's a query relative . as i have a similar roof type to yours, albeit in cheshire. basically, it's SE facing, 40 deg. no shading. i am wondering if it's worth considering PV, as sun is only on this side of the roof till around 2.00p.m, at which time, shading from the chimney would affect it for a whiloe, and then the sun would be on the NW side, which is subject to shading from trees.
My panels also only receive sun until mid-afternoon. In any case, the best generation is always when the sun is directly in front of the panels.
I put the following on another topic yesterday, which gives an idea of generation:
On a nice day, power generation typically looks like this (in recent weeks,
before the clocks changed!):
7am: 0.5kW (0.5kW total, 3% of day's total)
8am: 1kW (1.5kW total, 9% of day's total)
9am: 2kW (3.5kW total, 20% of day's total)
10am: 3kW (6.5kW total, 37% of day's total)
11am: 3kW (9.5kW total, 55% of day's total)
12noon: 2.5Kw (12kW total, 69% of day's total)
1pm: 2kW (14kW total, 81% of day's total)
2pm: 1.5kW (15.5kW total, 89% of day's total)
3pm: 1kW (16.5kW total, 95% of day's total)
4pm: 0.5kW (17kW total, 98% of day's total)
5pm: 0.25kW (17.25kW total, 99% of day's total)
6pm: 0.1kW (17.35kW total)
In other words: a rapid rise in the mornings, followed by holding close to the peak for an hour, followed by a steady trailing-off afterwards.
On a reasonably good day, you can see that
before the clocks changed:
by 10am I have over one-third of my day's quota.
by 11am I have over half of my day's quota.
by noon, I have over two-thirds of my day's quota.
by 2pm I have almost 90% of my day's quota; what happens after 2pm is negligible (when the sun has gone the other side of the house and my panels are effectively in shade).
So with a SouthEast-facing system, I would not be particularly concerned about where the sun is after 2pm.
What I would be concerned with, is whether you like the likely payback relative to the cost, given that the Feed-in-Tariff has recently been reduced to 21p.
Personally, I think it is still viable, but, unlike a bank account where the money can be got back at any time, the outlay on the panels is dead money and 1/25th of their cost should be deducted from the annual revenue they generate.
Also be wary of salesmen using high inflation expectations and high energy price increases to flatter the "profit" calculations when they quote you.
Let's say my 3.6kW (3.75kWp) system cost £10k - for argument's sake.
I must "depreciate" 1/25th of £10k (£400) each year to reflect that, unlike a bank account, I won't be able to ask for my money back.
I'm likely to generate around 3000kWh according to the government SAP calculations.
At 21p FiT, plus 0.5x3.1p for "export tariff", that would be £677 pear year in payments, plus about one-third savings on my electricity bill (about £150 per year).
From that £677, I must "depreciate" the £400 from not being able to get my money back from the panels, and can add-in what I save in electricity.
This leaves me with £677-400+150 per year, which is £427 per year, on £10k, which is 4.27%
The FiT payments have inflation linking, so if inflation and the cost of power sticks to the Bank of England's target of 3%, we can add that to the 4.27% "return", for a total return of 7.27% per year.
Or you could view it as a 4.27% bond, with inflation linking.
If, like some on here, you believe that power prices will continue to soar, or if inflation remains higher than the Bank of England's targets, then the gains and savings you make form PV will be even better.
But I prefer to suggest a "baseline" scenario, to avoid disappointment.
