The Great 'Get Paid To Generate Energy' Hunt

ChrisJD

Hi i have a 2.3kw system and my inverter is a 3kw..i have spoken to a couple of people in the course of my line of work and their systems have on occasions put out kwh than the system ie one guy
had a 2.5kw and he acheived 2.56kwh at some points..I personally ywould of thought you need an inverter to at leasy match the capability of the system?

Speaking to a pretty clued-up technical guy at a potential supplier, his take on the situation was that the bigger the inverter, the greater the losses. A lot of the time, the panels are operating at low output. Averaged over the year, it can be more efficient to size the inverter for a little less than the peak installed power. The energy lost during the short time when the panels are at full power is more than compensated for by greater efficiency the rest of the time.

Dave_Fowler

smellypunks wrote: »

Like everyone here I am interested in the idea of micro generation. But I cant help but feel it is still to early. I am thinking that if you worked the figures considering compound interest on an a mixed investment of stock and bonds, which would be held in an ISA invested over two years (£10,200 ISA limit per year). You could see a better value investment.


Option one stock/bond mixed portfolio
So £18,000 invested (in said mix share/bonds in ISA) for 19 years with average 7% interest APR could leave you with an investment worth £65,097.50

VS

Option two 3.5kW PV system
Saving £1,236 a year for 20 years 24720+18000= £42,720.00




Notes/issues/unknowns

• Now you might say 7% is not realistic
• Increasing fuel cost would mean larger than £1,236 per year savings
• How much will 3.5kW PV system be worth after 20 years? Not £18,000!
• Exist from stock/bond investment would need to be staggered or could end in tears if timed badly
• Cant touch money or feel saving for at lest 10 years stock/bonds are long term investment

But you want to feel the savings now
If you did go for Stock/Bond mix in an ISA rap you could do a mix of income and reinvested compound stock. You would see some cash but doing that would impact on the compound gain.

Installation grants
One last thing I know the government instalment grants are no longer around but there are still lottery grants (and others) for installation for Non-Profit Organisations if you could tap that for say 30/40% installation cost then it would be a different ball game.

Final word
I am not trying to put you off but maybe slow you from diving it to an investment that to me does not seem ripe just yet.

As I explained in my original posting, "I am about to retire" so I am looking for an alternative to a standard pension investment and one which will provide a steady annual index linked income for my future years.

I have been saving my money in various bonds / ISAs / annuities etc for many years now and it is time to reap some benefits. The idea of locking away money in a 20-year ISA is fine for someone in their earlier years but the lure of £65k in 20 years is not appealing to me - but it might be to the children.

I'm effectively looking from the other end of the telescope - not at what I might get in 20 years time, but what I can get for the next 20 years.

As you will see in a recent post, I did go ahead and purchase a system. The original idea of a 3.5kWp system did not materialize because of a limited roof space, but they did fit 2.96kWp - at a lower cost.

But lets keep with the original figures:- 'invest' £18k in a PV system and receive £1,236 in FITs in the first year. I use the term 'invest' loosely as has been pointed out before, the money is tied up on my roof and except for selling the house no part of it could be recouped.

The £1,236 is index linked, which this year is a 3% increase. If I were instead to invest the money in some financial institution the £18k would have to grow by 3% per year if it is to keep up with the current rate of inflation (=£540). If I were also to take an income of £1,236 in the first year, the interest on the £18,000 would have to be £1,776. (Withdraw £1,236 and leave £540 interest).

Taking these figures, I would need to find a flexible investment (one where I can withdraw some interest and leave the remainder) which would produce 10% annual tax free interest.

There may be such schemes available - let me know, I could just about manage to find another £18k

Dave

Cardew

Dave,
Without going into the figures in any detail, you are simply treating an investment in a PV system as an annuity - which IMO is exactly the way such an investment should be viewed.

Dave_Fowler

Cardew wrote: »

Dave,
Without going into the figures in any detail, you are simply treating an investment in a PV system as an annuity - which IMO is exactly the way such an investment should be viewed.

Exactly! Now lets see if anyone can come up with a better suggestion.

KG-THPP

ChrisJD wrote: »

Speaking to a pretty clued-up technical guy at a potential supplier, his take on the situation was that the bigger the inverter, the greater the losses. A lot of the time, the panels are operating at low output. Averaged over the year, it can be more efficient to size the inverter for a little less than the peak installed power. The energy lost during the short time when the panels are at full power is more than compensated for by greater efficiency the rest of the time.

So your clued up guy's advice is to throw away 2~3 pannels worth of electricity when the sun is shining at its best, in order to save a few percent when the suns not shining? I would like to see the maths he's done on that one.

PS. These systems with the feed in tarrifs are ment to reduce living costs in a household, not to act as a sort of pension. Do with your savings what ever you would do with any other surplus in your budget.

PPS. The key to rent a roof schemes and farmers wind turbines is to control the electricity tie in point with the grid, if you want to do that then you may be paying the electricity bill for the person who buys the house off you.

ChrisJD

KG-THPP wrote: »

So your clued up guy's advice is to throw away 2~3 pannels worth of electricity when the sun is shining at its best, in order to save a few percent when the suns not shining? I would like to see the maths he's done on that one./QUOTE]

There is software downloadable from the inverter suppliers' web sites that enables you to check compatibility with particular panel configurations, and calculate output. The results are not always what you would assume.

The key factor is that panels spend a great deal more time at low output than at maximum.

Dave_Fowler

ChrisJD wrote: »

KG-THPP wrote: »

So your clued up guy's advice is to throw away 2~3 pannels worth of electricity when the sun is shining at its best, in order to save a few percent when the suns not shining? I would like to see the maths he's done on that one./QUOTE]

There is software downloadable from the inverter suppliers' web sites that enables you to check compatibility with particular panel configurations, and calculate output. The results are not always what you would assume.

The key factor is that panels spend a great deal more time at low output than at maximum.

Looking at virtually every manufacturers website the inverter manufactures suggest using inverters with a power rating about 10% less than the peak panel rating.

I agree with you that the panels spend the vast majority of the time generating under their peak output. I work from home and the power meter display sits on my desk, so it is easy for me to keep a check on the generation.

In the past 3 months there have been five occasions when my 2.96kWp system has limited the peak power of my 2.65kW inverter. The time it has been limiting has lasted no longer than a few minutes, but let's say an hour on each of the 5 occasions.

The three months include two summer months, July and August. Today the sun is bright, but as we are now in October the radiation is lower than in the summer and the peak power today has been 2.45kW - no limiting.

Let's double the number of days that the system limits to allow for one whole year i.e. 10 hours of limiting.

During the time of limiting, I would have lost a maximum of 300W x 10 hours i.e. 3kWh. The FITs loss is therefore about £1.24p in the year. I could have purchased a larger inverter, but the next size up would have cost me about £100 extra. Pay-back in 80 years?

Strangely, the efficiency of one model of an inverter compared with its higher powered counterpart does not always stack up; for instance a Sunnyboy 3000W inverter is more efficient at 1kW output than a Sunnyboy 2500W inverter at the same power output.

Dave

KG-THPP

ChrisJD wrote: »

There is software downloadable from the inverter suppliers' web sites that enables you to check compatibility with particular panel configurations, and calculate output. The results are not always what you would assume.

The key factor is that panels spend a great deal more time at low output than at maximum.

Ah indeed. Using that software I am shown that inverter efficiency rises by 0.2% if undersized by 500W.

John_Pierpoint

Dave_Fowler wrote: »

The £1,236 is index linked, which this year is a 3% increase.

Dave

Which inflation index is being used for FiT's?

Us pensioners tend to suffer a higher rate of inflation than the productive savings & net investing younger members of society.

Dave_Fowler

John_Pierpoint wrote: »

Which inflation index is being used for FiT's?

Us pensioners tend to suffer a higher rate of inflation than the productive savings & net investing younger members of society.

According to my information it's the retail price index which is used for FITs payments .

The RPI is currently at 4.7% and the alternative measure of the inflation, the consumer price index is 3.1% (Source:- Office for National Statistics). So I should have used the higher figure in my calculations.

Dave