Solar

sugarwalsh

Hi all,

We have been considering getting solar for a while now, mainly for financial reasons (with 4 kids the bills just seem to be ever rising) and partly for ethical reasons.

I have to admit to not knowing a great deal about it - I have been looking at some of the threads and I can follow most of it, just not all the technical stuff! So, last night we had a rep around to discuss the possibilties of installing it and today we have a quote. I wondered whether anyone minded having a little look and let us know if they think that it is reasonable and whether it is worth it.

We live in Lancaster, our house faces West at the front. We have discussed putting 8 on the front and 8 on the rear with two inverters. This would be a 4kw system, with suggested output of 2789kw/h per annum. Does this sound ok? The cost quoted is £6900 - I susect my husband will drive the price down now we have an offer.

Things to note - I am a stay at home Mum so I can do all the chores during daylight hours and as the kids are home in the summer during daylight hours we can make sure they have showers during these hours (We can switch to an electric shower if it is worth it?) I can do all cooking during these hours etc to help. Our current electricity bill is around £75 per month, as is the gas. I would like to lower these as much as possible. We would have to get finance for the installation.

Do these figures stack up? Are we EVER likely to pay it off/benefit from lower bills and the like?

I thank you in advance and apologiseif I have misunderstood some of the quote!

Megan

Martyn1981

Hiya Megan, flying visit, will pop back later.

Just to say I did a very quick check on Lancaster and got an estimate of 2,855kWh's pa. So the estimate looks accurate.

Bye for now.

Mart.

sugarwalsh

Thank you! I did trust the guy, and the little research I have done he confirmed. Plus I managed to question him on a few bits and pieces, but it is always best to check, especially when we are committing to something so expensive.
Megan

rogerblack

In principle, you could use a 4kW limited inverter which can cope with two banks of panels, and two 3kW arrays (12 panels) on east and west.
You will never (?) get the sun directly shining on both the east and west at the same time - so the inverter will never reach 4kW (or very very rarely), but the generation will be better spread over the day.

It depends on what finance you can get.
The above suggestion will lead to more revenue, and perhaps a faster payback, but will increase the initial investment.

The numbers mentioned above seem reasonable - but only if your panels are not shaded.
East and west facing panels are somewhat more sensitive to things on the horizon - their peak in generation is early and late in the day - when the sun is comparatively low.

sugarwalsh

I understood it was to be 16 panels in toatal, does that sound right? And I will question the 2 inverters if you think we should?

The house has no shade - we live on a wide street. I would estimate the rear of the house gets sun from around 7am - noon and the front from about 2-sun down (Ish) if that makes any sense? It is a larger than average 3 bed semi so there is plenty of roof space.

Thanks for the advice.

rogerblack

sugarwalsh wrote: »

I understood it was to be 16 panels in toatal, does that sound right? And I will question the 2 inverters if you think we should?

Basic idea is that at the moment - you have 4kW of panels - and 4kW (total) inverter. At noon in summer, on a south-facing roof, you would get 4kW output.
However.
Due to geometry - you will never get full sun on east and west panels at any time.
If you go up to 6kW of panels - separated onto east and west roofs - but still with a 4kW limited inverter - you get the 4kW rate for FIT - but your total generation on a good (or bad) day will be 50% higher.
You do need an inverter that can properly cope with two different strings, with different output, if you have an array split over an east and west roof.

spgsc531

rogerblack wrote: »

Basic idea is that at the moment - you have 4kW of panels - and 4kW (total) inverter. At noon in summer, on a south-facing roof, you would get 4kW output.
However.
Due to geometry - you will never get full sun on east and west panels at any time.
If you go up to 6kW of panels - separated onto east and west roofs - but still with a 4kW limited inverter - you get the 4kW rate for FIT - but your total generation on a good (or bad) day will be 50% higher.
You do need an inverter that can properly cope with two different strings, with different output, if you have an array split over an east and west roof.

Are you sure about that?

How would you get the 4kW rate with 6kW of panels?

Wh05apk

I am having a 4kw installation installed next week, but had considered increasing to 4.5kw or even the max of 7.5kw as that is what would fit on our roof, but was told it would be almost impossible to get agreed, the tariff would be based on the panel output, not the invertor, and 7.5kw could mean going to 2 or 3 phase electrics at massive cost.

rogerblack

spgsc531 wrote: »

Are you sure about that?

How would you get the 4kW rate with 6kW of panels?

Because the generated output can never exceed 4kW, as it is limited by the inverter.
(In addition to physics)

Martyn1981

rogerblack wrote: »

If you go up to 6kW of panels - separated onto east and west roofs - but still with a 4kW limited inverter - you get the 4kW rate for FIT - but your total generation on a good (or bad) day will be 50% higher.

Hiya Roger, unfortunately, the FIT rate is based on the kWp of the panels.

This flies in the face of the legislation, describing the maximum continuous output the system is capable of, but OFGEM aint budging, and nobody wants to incur the legal bill of challenging it.

Mart.

spgsc531

rogerblack wrote: »

Because the generated output can never exceed 4kW, as it is limited by the inverter.
(In addition to physics)

In addition to you being wrong?