is PV worth it - 9 panels facing west

[Andrew54]

I'm starting to think a PV system just isn't worth investing in for my roof, considering only 9 panels and the roof faces just 18 degrees south of due west.

Another factor seems to be how much of the electricity generated could be used, rather than sold. I'm thinking of it all ways round, but I can't use much power through the day, especially in summer.

Your thoughts please.

 

[Gavin A]

all depends how much you're getting charged for the system really, and if the money is doing anything useful / needed for something else etc.

 

[Andrew54]

all depends how much you're getting charged for the system really, and if the money is doing anything useful / needed for something else etc.

£5,500 no and no.

 

[FB.]

£5,500 no and no.

That's quite expensive for 2.25kW.

Assuming no shading issues from trees, telegraph poles, other buildings etc, and a normal 30-40 degree roof pitch, I'd expect annual generation around 1900kWh.

That'd be worth around £270 per year from Feed-in-Tariff.
About £40 per year export tariff.
Bill savings, assuming 25% in-house usage: £60.
Total annual benefit: £370.

Even assuming 7-8% annual energy inflation and 3-4% RPI inflation that's 10/11-year payback, which I consider to be too long. More than ten years is too long.

However, Gavin's Leeds Solar (he's got a link in his signature) offer 2kW for £3995 (probably £4500 for 2.5kW) and the payback is a respectable 8-years.
Leeds Solar | PV price comparison

I initially worried about having "cheap" Chinese panels (in my case Kinve) but my system has almost completed a year of perfect, trouble-free operation (and exceeded the SAP estimates). I was also offered Sanyo/Panasonic panels at a 30% higher total cost of the system. I wondered whether I should go with a well-recognised brand, but, given the recent downgrading of Panasonic/Sanyo's credit rating to near-junk, even the premium panels may have nobody backing the guarantee in a few years time. The expensive panels only show a small improvement in performance over the lower-cost panels. Some people reckon no difference at all, since 250Watt is 250Watt - it's just that premium panels pack the same power into a smaller panel.

Gavin's a decent, knowledgable chap. If he's not in your area, I suspect that there are others on here who can easily beat £5500 for 2.25kW.

On the subject of payback - my 3.75kWp system, on the old, higher FiT rate of 45.4p, has a likely payback around five years. A fried of mine has a 21p FiT and their 4kW system has a seven-year payback. So an eight-year-payback is not that bad at current heavily discounted prices (compared to late 2011 and early 2012 when solar cost almost twice as much to buy, and had twice as much FiT payments).

 

[balbecdaze]

I think you could definitely get a better price - what part of the country are you in?

 

[Andrew54]

It's a 45 degree pitch roof.

I'm trying to understand your figures FB.

That'd be worth around £270 per year from Feed-in-Tariff. I understand that bit.
About £40 per year export tariff. What is export tariff please?
Bill savings, assuming 25% in-house usage: £60. 25% in-house usage makes sense, but don't we get paid something for the other 75%?
Total annual benefit: £370.

Read more: http://www.electriciansforums.net/p...worth-9-panels-facing-west.html#ixzz2DAcBe9Av

 

[FB.]

It's a 45 degree pitch roof.

I'm trying to understand your figures FB.

That'd be worth around £270 per year from Feed-in-Tariff. I understand that bit.
About £40 per year export tariff. What is export tariff please?
Bill savings, assuming 25% in-house usage: £60. 25% in-house usage makes sense, but don't we get paid something for the other 75%?

Until smart meters are installed in the next few years, it is assumed that half the power is used in-house, and half goes to the grid.
The export tariff is worth about wholesale rates - around 4.5p - for half of what you generate.

In the long term, a smart meter will allow you to be paid precisely, but until then it's assumed to be 50/50 used in-house/exported to the grid.

 

[Graeme Harrold]

If you have an immersion heater, then add Immersun and boost your savings. If you are out during the day, you will heat your water for free. If you dont have tanked hot water add it at the same time and you should be able to have that work done at 5% VAT too....

 

[Andrew54]

Until smart meters are installed in the next few years, it is assumed that half the power is used in-house, and half goes to the grid.
The export tariff is worth about wholesale rates - around 4.5p - for half of what you generate.

In the long term, a smart meter will allow you to be paid precisely, but until then it's assumed to be 50/50 used in-house/exported to the grid.

Sorry I'm still struggling to understand this bit. If 50/50 is assumed, why did you mention 25%. And why did the outfit quoting mention 100%???? You both gave a figure around £40 for the 'export' but you gave a bill saving of £60, they said bill saving of £250.

My present elec meter is very new, and small, is it still not a smart meter? Thanks again, but a bit more explanation would be good.

 

[gizmo]

Last time I had someone round for this, he opened my eyes a little ! Now what he suggested to me I have is a 4kw array, eight panels on the sw side, eight on the ne side ! I pointed out to him that surely that won't give me the best return, and surely I'm wasting my money on the ne side. His reply was the government is paying me an ASSUMED rate, there fore, it could be pitch black and I'd still get my feed in tariff!

 

[Andrew54]

If you have an immersion heater, then add Immersun and boost your savings. If you are out during the day, you will heat your water for free. If you dont have tanked hot water add it at the same time and you should be able to have that work done at 5% VAT too....

Yes I've read up on immersun but not convinced. First we don't use much hot water and second it seems rather expensive if it doesn't last many years.

 

[balbecdaze]

@ gizmo !!! where to start ...:6:

 

[balbecdaze]

The only assumption is, as FB. says, that 50% of the electricity you generate is exported. FB. was using the 25% usage figure to calculate your electricity bill savings.

Your FiT is paid based on a reading from your generation meter, which shows exactly how much energy you have generated.

 

[FB.]

Sorry I'm still struggling to understand this bit. If 50/50 is assumed, why did you mention 25%. And why did the outfit quoting mention 100%???? You both gave a figure around £40 for the 'export' but you gave a bill saving of £60, they said bill saving of £250.

My present elec meter is very new, and small, is it still not a smart meter? Thanks again, but a bit more explanation would be good.

Only a few houses have smart meters at the moment. While it is theoretically possible that you have one, it is extremely unlikely. I don't know anyone who has a smart meter, nor anyone scheduled for one any time soon.

I'll elaborate a bit on where the gains are coming from.

Inside my house is an electicity meter attached to the solar inverter. It is the same model as is out in my meter box.
This "generation meter" records what the inverter pumps out - sitting between the inverter and my consumer unit (fuse box).
Until smart meters are fitted, the only meter that matters is the generation meter.

If I had just had my array installed, I'd get:

1. Feed-in-Tariff:
14.4p for every unit generated, according to the generation meter. 14.4p x 1900kWh = £273.60.

2.
4.5p for half of all units generated, under the assumption that half was used in-house and half went to the grid. Until smart meters are fitted, this is used as an approximation. When smart meters are fitted it will measure precise two-way flows and if all of your power gets exported you'll get 4.5p x 1900kWh = £85.50, but for the next few years it will be assumed to be 50% export, so you'll get £42.75.

3.
If I generate 1900kWh and use it all, at a value of 12.5p per kWh, that's "worth" £237.50 per year in bill savings.
In reality it is almost impossible to use it all due to either not needing the power, or the variability from minute-to-minute on days with a mixture of sunshine and cloud.
If you think you're not likely to use as much of the power, it is probably fair to assume 25% in-house usage, so that £237.50 of potential gains drops to £59.38 of actual gains if you only manage to use 25% in-house.
So the company assuming that you'll use all the power are being very optimistic. It's almost impossible to do so due to the erratic nature of solar generation.

 

[FB.]

The only assumption is, as FB. says, that 50% of the electricity you generate is exported. FB. was using the 25% usage figure to calculate your electricity bill savings.

Your FiT is paid based on a reading from your generation meter, which shows exactly how much energy you have generated.

Yes, I was using 25% in-house because the opening poster said "....I can't use much power through the day, especially in summer...."

So I thought it would be fair and realistic to assume 25% in-house (if nothing else the fridge will use a few hundred Watts of power on-and-off during daylight hours).

Personally I've been using about half of the power in summer and about three-quarters in winter. But I am at home a lot of the time and can take advantage.