Solar panels - a few questions.

Wilding

I signed up at the weekend for a 4kW roof solar system, and a similar system for my Mum (aged 76). We had three quotes, two from big glossy firms with slick salesmen driving brand new Audi's, and one from a local electrician. All from the MCS website. The local guy got the order.

I am on MSE Energy Club, so we get the best rate currently 9.4/kWh.

My mum is a non-switcher because she fears she will by paying everybody for her energy, and I speak from experience when my account in credit (by over-debiting the bank account) is not returned when I switch - unless I quibble.

Here are my questions.

1. Can anyone say what kind of output (Wattage) can we expect from a 4kW system on a cloudy January day?

2. What kind of power does a Hotpoint Aquarius Tumble drier draw on full power? (Its website is not clear on this).

3. Is there a penalty from the tariffs if I have a system greater than 4kW? (One salesman said there is, another said not)

4. What's the pros and cons of 285W over 250W panels?

5. What the pros and cons over Chinese made panels over non-Chinese?

6. Black panels, or blue & aluminium edged panels? That's the story between the two.?

7. I'm paying £6600 for a non-micro inverted (2 string) system? is that reasonable?

8. My mums is a £6900 but has A-frames for her flat roof. Reasonable?

9. Is using electric storage heaters (like a daytime version of Economy 7) a viable means of capturing daytime solar energy and using it for heating in the evening during the winter months? And if so, what units are best? (We don't have immersion tanks)

10. Is there a big difference between which panels having a greater degradation rate, and how is that measured from one manufacturer to another?

11. What is the rate of VAT on a solar installation? Labour and Hardware?

12. I am on MSE Energy club currently with GB Energy and switch frequently.

a) Do we get paid the feed-in (4.?p/kWh) and export tariff (13.?p/kWh) from our MSE supplier? Or is this coming from elsewhere? - And

b) How often is is paid?

c) Who reads the Feed-in and export tariff meter readings? - how does that work?

Really appreciate your help?

silverwhistle

Post this in the Green & Ethical Money Saving sub-forum for a speedier response. You may be able to squeeze a bit from your suppliers, but they're certainly not the 'taking the p*ss' quotes we sometimes hear about, particularly given the additional requirements.

NigeWick

1. Not a lot but the annual average won't be too far out for the year.

2. Read the instruction manual.

3. You go on to a lesser "business" rate.

4. You pay your money and make your choice. 4kW is 4kW.

5. See 4.

6. Your choice.

7. Seems about right. I was quoted more and less than that.

8. Probably.

9. You'd need to monitor electricity production and haven'y got a clue as we don't have them.

10. Not enough to matter.

11. A percentage of what the total is. The estimate/bill should let you know.

12. The money comes from the government and your supplier, paid by the supplier.

Quarterly.

You read from the inverter and give the readings to your supplier. First Utility sent me a reminder with link to submit reading to.

Wilding

I really appraciate your answers, this is fab!

Just a few more Q's

1. Can a 4Kw system produce 1Kw on an overcast January day?

b) If No, then what capacity system is needed to get a kW on an overcast January day?

2. Can I add more panel's later, such as on an extension? Is it easy to do?

Martyn1981

Wilding wrote: »

Here are my questions.

1. Can anyone say what kind of output (Wattage) can we expect from a 4kW system on a cloudy January day?

See section 5 of the PV FAQs. But, really you'll be guessing, and will depend on orientation, and especially pitch at that time of your. It could be pumping out several kW's for a few hours, or in black cloud, be almost zero.

3. Is there a penalty from the tariffs if I have a system greater than 4kW? (One salesman said there is, another said not)

The 4-10kWp rate is 10% less than the upto 4kWp rate, and applies to the whole install, so 4.01kWp would attract the lower rate.

4. What's the pros and cons of 285W over 250W panels?

If space is limited, then 285Wp panels can achieve 4kWp with 14 panels, rather than 16. 285's will cost a little bit more per Wp, (not too much) but if space is limited they are probably worth it.

7. I'm paying £6600 for a non-micro inverted (2 string) system? is that reasonable?

It's ok, but quite a few people are now achieving prices in the £5k to £6k range. Some less than £5k.

8. My mums is a £6900 but has A-frames for her flat roof. Reasonable?

Possibly, hard to tell, but have you checked about planning permission. I believe permission is needed if you are changing the pitch of the roof?

9. Is using electric storage heaters (like a daytime version of Economy 7) a viable means of capturing daytime solar energy and using it for heating in the evening during the winter months? And if so, what units are best? (We don't have immersion tanks)

For the cost of investment, probably not worth it. However, you can switch on a cheap low powered oil filled radiator when you have excess leccy, but be careful not to import expensive leccy. In the winter generation will be lower, and excess (above normal demand) even tighter.

If it's a nice sunny day, then I can often leave a 400W rad running during most of the sunlight hours from Feb onwards. This won't heat your property, but can keep the chill off a room if you turn the GCH off once warm in the morning.

11. What is the rate of VAT on a solar installation? Labour and Hardware?

5% if done under the MCS rules and regs. For FiTs, the install/installer has to be MCS.

I've tried to answer within your post, but have ignored the questions on looks and comparisons, as that's really up to you.

Mart.

Martyn1981

Wilding wrote: »

I really appraciate your answers, this is fab!

Just a few more Q's

1. Can a 4Kw system produce 1Kw on an overcast January day?

b) If No, then what capacity system is needed to get a kW on an overcast January day?

2. Can I add more panel's later, such as on an extension? Is it easy to do?

Hiya again.

1. Too hard to answer. A 50d pitch south facing roof will work reasonably well in Jan, though it'll work 4x better in June. Whilst a 20d pitch east facing roof will be very poor in January and about 8x better in June.

What does overcast mean, a white sky can reflect light, even onto panels not facing the sun, but a dark grey or black sky can shut a system down.

2. Yes you can, but you'll need the room, and will need prior permission from the district network operator (DNO) if your potential export is greater than 3.68kW. See section 10 of the PV FAQs.

It's far better to consider going big in one go, as there are a lot of fixed costs, such as scaffolding, and if done at the same time, you'll be able to share an inverter. It may be worth having a large system that is capped at 3.68kW, since they spend a lot of time below max. The 10% FiT drop isn't that bad, when you think about it, but since it affects the whole install, it might not be a good idea if you only go over 4kWp by a small amount, say 4 to 4.5kWp. Best to go 5kWp+ if this is practical.

Mart.

matelodave

Have a look here http://solarelectricityhandbook.com/solar-irradiance.html


fill in the information regarding your location, angle of the panels to the sun and direction that they point and you'll get a figure which averages the percentage of what you might expect per day although some days will be worse and some better - non if it's snowing
For instance the calculator for my location give a number of 1.25 in January and 4.28 in July. Multiply the size of your array (4kwp) by the number which gives about 5kwh/day in Jan and 17.12/day in July.

gazapc

Wilding wrote: »

10. Is there a big difference between which panels having a greater degradation rate, and how is that measured from one manufacturer to another?

As this one hasn't been answered....

You would expect a 2-3% drop in year one caused by various processes and then a 0.75% per year drop after that. So after 20 years the panels will still be producing 80% of the nameplate capacity.

Other than the high end panels like SunPower you won't find too much difference between the big manufacturers such as Suntech, Trina etc...The existing litrature and studies done support a 0.5-1% degradation rate per year although some installers do claim less. It is still a bit of an unknown and I spend a fair bit of time at work trying to explain it to investors making big investment decisions! We won't have a better understanding for a few more years as such a vast amount of PV has only been in place for a couple of years.

Most manufacturers will guarantee a level of around 0.75% per year though; I would be interested to hear on a domestic scale if there have been any sucessful claims, on the large scale ground mount systems I am not aware of many claims being made.

Panels are put through standardised accelerated testing, for example cycling a few thousand times from high temperatures and humidity to freezing conditions and back again. This picks up defects and checks build quality but isn't really quite the same as degradation.

Martyn1981

gazapc wrote: »

As this one hasn't been answered....

You would expect a 2-3% drop in year one caused by various processes and then a 0.75% per year drop after that. So after 20 years the panels will still be producing 80% of the nameplate capacity.

First UK grid connected PV system 95% efficient 20 years later

The UK’s first grid connected solar system has been tested on its 20th anniversary, to find it still has a 95% generation rate from its initial installation 20 years ago.

The system was predicted to decline in efficiency by 20% from the panel’s original performance over 20 years.

Not conclusive proof, or proof at all really, but my system has performed at between 99% and 108% of PVGIS target from 2011 to 2014. With the highest figure in 2014, and the lowest in 2011. This year currently predicting 106% (if the rest of the year is average). However, annual figures will vary with sun levels, and a possible 0.5%pa degradation rate will easily be lost in the roundings ..... at first.

Mart.

gazapc

Martyn1981 wrote: »

First UK grid connected PV system 95% efficient 20 years later




Not conclusive proof, or proof at all really, but my system has performed at between 99% and 108% of PVGIS target from 2011 to 2014. With the highest figure in 2014, and the lowest in 2011. This year currently predicting 106% (if the rest of the year is average). However, annual figures will vary with sun levels, and a possible 0.5%pa degradation rate will easily be lost in the roundings ..... at first.

Mart.

http://www.nrel.gov/docs/fy12osti/51664.pdf

This is one of the most comprehensive studies (by NREL in the US) with key graphs on page 6 and covers many systems from around europe and the world. There is a fairly wide variance but the average is around 0.5-1% per year. Infact looking at the map on page 2 that system could have even been in the study as there is a red dot near Nottingham...

Martyn1981

gazapc wrote: »

http://www.nrel.gov/docs/fy12osti/51664.pdf

This is one of the most comprehensive studies (by NREL in the US) with key graphs on page 6 and covers many systems from around europe and the world. There is a fairly wide variance but the average is around 0.5-1% per year. Infact looking at the map on page 2 that system could have even been in the study as there is a red dot near Nottingham...

Thanks. Am I reading the summary conclusion table correctly that post 2000 monocrystaline silicon has an average degradation rate of 0.36%pa? Because that's about half of what I expected. Polycrystaline isn't looking too bad either.

Mart.