Solar Panel Guide Discussion

KevinG

Wow. Total UK capacity more than doubled in just 6 weeks.

http://www.solarpowerportal.co.uk/news/decc_reveal_deadline_week_figures_2356/

Cardew

KevinG wrote: »

Wow. Total UK capacity more than doubled in just 6 weeks.

http://www.solarpowerportal.co.uk/news/decc_reveal_deadline_week_figures_2356/

It would be interesting to see how many of those were for Rent - a Roof companies.

Sam_Lewis_2

sly_dog_jonah wrote: »

Why do companies use wildly differing claims of the amount of generated energy you will use in the home? The EnergySavingTrust base their calculations on 25% usage, but most companies quote far higher or use the deemed 50% (which is only accurate for deemed export, not the usage).

One blog entry on used a 'usage figure' of 70% of the generated electricity to come up with a 10.7% return. Clearly such claims wildly exaggerate the likely usage of electricity possible from such a large system.

The SAP is fine for estimating generated output, but some over-egging of the financial returns is clearly prevalent across the industry.

Firstly i can appreciate your concerns and unfortunately some companies will manipulate these figures to make their systems seem more attractive to potential customers. Although I can only speak for the company that I work for, we assume 50% usage and 50% export with regards to the electricity produced from any given system. However, we always make the customer aware that these savings are reliant upon their lifestyle and how much of their electric they use in the daytime.

The feed in tariff element of the returns is easier to accurately calculate and obviously forms the majority of the savings.

zeupater

Sam_Lewis wrote: »

Firstly i can appreciate your concerns and unfortunately some companies will manipulate these figures to make their systems seem more attractive to potential customers. Although I can only speak for the company that I work for, we assume 50% usage and 50% export with regards to the electricity produced from any given system. However, we always make the customer aware that these savings are reliant upon their lifestyle and how much of their electric they use in the daytime.

The feed in tariff element of the returns is easier to accurately calculate and obviously forms the majority of the savings.

Hi

Perhaps it would be good practice to stop doing this then, as it is rediculous, and use a more realistic figure, say a standard fixed saving assumption of somewhere around £100 for any domestic system over 2kWp, and then "make the customer aware that these savings are reliant upon their lifestyle and how much of their electric they use in the daytime".

Take a household with a 3300kWh/year electricity usage ... would it be realistic to say that 50% of generation being self consumed would apply equally to systems rated at 2kWp, 3kWp, 4kWp and 10kWp ? ... considering that a 10kWp system would produce around 9000kWh.a is there an obvious issue ? .... (9000/2)>3300!

HTH
Z

sly_dog_jonah

Sam_Lewis wrote: »

Firstly i can appreciate your concerns and unfortunately some companies will manipulate these figures to make their systems seem more attractive to potential customers. Although I can only speak for the company that I work for, we assume 50% usage and 50% export with regards to the electricity produced from any given system. However, we always make the customer aware that these savings are reliant upon their lifestyle and how much of their electric they use in the daytime.

50% deemed export is perfectly reasonable, since most FIT providers will ignore any export (not generation) meter you have paid to install, which is why most installers say don't bother. But I have serious reservations about the deemed usage of 50%.

Since commissioning late October our electricity usage has only reduced 12% (compared to our annual average of 3900kWh/year). However that 12% figure is probably well under what we will save over the whole year since everyone uses electricity more during winter (lights on for longer) and PV generates for much less of the day (due to less sun) and at lower power. Our appliances are only a year old and so they have very good energy efficiency ratings. I work from home, so we've already changed to daytime running of appliances.

I'm hopeful we will save around 30% over the course of 12months, but as the 4kWp array is SE facing the generation will tail off in the late afternoon so it won't help with evening cooking (using electric). This is still some way short of 50% though.

Therefore I have to agree with zeupater. Using a fixed percentage as high as 50% for 'electricity savings', irrespective of the size of the array, is disingenuous. I would even disagree with the Energy Saving Trusts '25%' assumption, since the savings will tail off as the array size increases. zeupater's suggestion of a fixed amount of saving is likely to be far more representative of the true savings than any estimate using a percentage of the total generation.

The feed in tariff element of the returns is easier to accurately calculate and obviously forms the majority of the savings.

This is not quite so true since the reduction in the FITs rate. The reduction in FIT income now means the 'energy savings' element of the total return makes up a far bigger amount than it used to:

• Before the cuts in FIT rate, the 'usage savings' as a percentage of the overall return (using a 50% usage assumption) was about 10% of the total return [the export income was around 3% and the FIT tariff made up the remaining 87%].
• Since the FIT cuts, the 'usage savings' as a percentage of the overall return (using a 50% usage assumption) is now around 18.5% of the total return. (For a 70% 'usage saving' that some companies are using, it comes out as around 24%.)

My argument then is that the return is now much more dependent on the actual energy savings, as this element of the return accounts for nearly twice as much of what it used to (18.5% versus 10%) if you use the 50% deemed usage assumption.

Sam_Lewis_2

zeupater wrote: »

Hi

Perhaps it would be good practice to stop doing this then, as it is rediculous, and use a more realistic figure, say a standard fixed saving assumption of somewhere around £100 for any domestic system over 2kWp, and then "make the customer aware that these savings are reliant upon their lifestyle and how much of their electric they use in the daytime".

Take a household with a 3300kWh/year electricity usage ... would it be realistic to say that 50% of generation being self consumed would apply equally to systems rated at 2kWp, 3kWp, 4kWp and 10kWp ? ... considering that a 10kWp system would produce around 9000kWh.a is there an obvious issue ? .... (9000/2)>3300!

HTH
Z

Firstly for the 2 and 3 KWp systems 50% usage of the amount generated would be a fair assumption because these systems are obviously producing less as a whole. A 4kw system produces around 3300 kwh/ a year and if we assume that the average household uses arounf half of its electricity during the daytime then again assuming 50% usage of the amount generated would not be unfair. With regards to a 10 kw system these are few and far between and you would have to have a huge electric bill to achieve 50% saving anyway but obviously the feed in tariff payments would be substantially higher anyway.

zeupater

Sam_Lewis wrote: »

Firstly for the 2 and 3 KWp systems 50% usage of the amount generated would be a fair assumption because these systems are obviously producing less as a whole. A 4kw system produces around 3300 kwh/ a year and if we assume that the average household uses arounf half of its electricity during the daytime then again assuming 50% usage of the amount generated would not be unfair. With regards to a 10 kw system these are few and far between and you would have to have a huge electric bill to achieve 50% saving anyway but obviously the feed in tariff payments would be substantially higher anyway.

Hi

Considering that 3kWp is 50% larger than a 2kWp, how can the answer in both cases be the same ?, then again the claim later in the post is that the answer for a 4kWp system is the same too .... The 10kWp system was simply to illustrate the point that the logic of assuming that 50% of generation will be self consumed is flawed .

As long as the system covers the baseload of the house there will be little difference in saving between any reasonably sized systems as the only difference becomes the ability to supply against 'peak' loads, such as the kettle, cooker, washing machine, dishwashers etc ... however, these high load appliances aren't used for long periods, therefore increasing the size of the array comes under the influence of the law of deminishing returns.

There are a number of people posting on these boards who have quite a lot of experience in pv over the years, including some with export meters, and there seems to be a general consensus that you're doing quite well if you can save £70 to £100 on your bill, we have a 4kWp system and save a little over £100 .....

In conclusion, it would therefore be unfair to claim that ...."A 4kw system produces around 3300 kwh/ a year and if we assume that the average household uses arounf half of its electricity during the daytime then again assuming 50% usage of the amount generated would not be unfair." .... because the assumption of 50% is flawed ... please feel free to check this out on the EST web site or even directly as they have a thread running on this forum (https://forums.moneysavingexpert.com/discussion/2867980) ...

HTH
Z

penrhyn

There may be widespread contamination of solar panels on boxing day due to the droppings from airborne reindeer, every household could be affected.

This danger is such that North American Aerospace Defence Command devotes all their resources to track it.

You can follow their efforts here

orrery

KevinG wrote: »

Wow. Total UK capacity more than doubled in just 6 weeks....

It is a sad indictment of the total UK installed capacity that it was even possible to double it in such short a space of time!

Cardew

orrery wrote: »

It is a sad indictment of the total UK installed capacity that it was even possible to double it in such short a space of time!

Very true!

Who can we blame for situating the UK so far North of the equator?

Those irresponsible people in Greenland are even worse than the UK. If they paid them, say, £5 per kWh in subsidies I bet they they would buck up their ideas!