Solar Panel Guide Discussion

Martyn1981

Sirlaughalot wrote: »

EST figures are freely available but where can you get the fore mentioned PVGIS figures from?

SL

Hiya SL, there is a walkthrough here, post #1 section 5:

https://forums.moneysavingexpert.com/discussion/3872445

Probably would have helped if I'd told you.

Mart

Sirlaughalot

Martyn1981 wrote: »

Hiya SL, there is a walkthrough here, post #1 section 5:

https://forums.moneysavingexpert.com/discussion/3872445

Probably would have helped if I'd told you.

Mart

Hi Mart,

What Estimated system losses are you using in your calculations?

Martyn1981

Sirlaughalot wrote: »

Hi Mart,

What Estimated system losses are you using in your calculations?

Hiya SL, are you getting hooked? This PV lark is addictive!

I left the system losses at default 14%. I was surprised that my generation wasn't lower as I have a bit of shading from one tree during winter months, and from a chimney to the SSW.

Been told, not sure if this is true, that 14% may be a little high as efficiencies (particularly inverters) has improved. So possibly they balance each other out, or the weather hasn't been as bad as I thought. Either way, I'd leave it at 14% if only to build in a little margin for yourself. Also if you're not sure if there might be some shading, perhaps knock a bit more off the total if only to prevent you being disappointed and over-stating total income.

This site is handy for comparing local sunshine levels to longer term averages:

http://www.metoffice.gov.uk/climate/uk/anomacts/

Choose sunshine, then a month or year or season etc.

Mart.

Sirlaughalot

Before i publish the results of company A i called RECC today just for clarification on two subjects (all 3 companies that quoted had RECC accreditation).. Only Company A left me a hard copy of the annual results/yr1 predicitions and NONE of the 3 companies advised me of the house energy certification requirement for the FIT payment.. The RECC rep said both these practices were against RECC member policy.

Company A is a nationwide solar panel provider with over 10 years experience. It adviced of a 3kw system due to me setting a limit of £6000. 12 JA solar panels (JAM6) on a 35 degree roof(pitch) on an orientation of 225 degrees south west.

The system on their figures produced an expected yr1 power generation of 2649kwh.returning a value of £655 on a investment of £6380.

The rep said the system would have paid for itself by year 7 end the inverter would be warranted for 20 years. The panels have a 10 year product warranty and a 25 year power output warranty to 80%

Any comments please feel free to post.

SL

Annual

Cardew

Sirlaughalot wrote: »

The system on their figures produced an expected yr1 power generation of 2649kwh.returning a value of £655 on a investment of £6380.

The rep said the system would have paid for itself by year 7 end

I am a little out of date on figures, but I believe below is correct:

2,649kWh x 14.9p = £394

50% of 2649 x 4.64p = £61

So £455 income, plus what you save on electricity bills which could be around £100. So £555 - not £655 would be more realistic.

You obviously have to take a guess at future inflation rates and Fuel inflation rate.

Also you must consider the lost interest on the £6380 which at, say, 3% is initially £190. That sum will be compounded.

For a fair comparison your inflation linked income/savings(the £555) would also be invested each year

So your first year savings will be in the order of £365.

You can use your own figures for inflation rates, interest rates, fuel inflation rates and in-house usage. However IMO the 7 years payback is just a joke. In fact double that(14 years) would be excellent - again IMO and that is assuming no repairs needed.

Sirlaughalot

Cardew wrote: »

I am a little out of date on figures, but I believe below is correct:

2,649kWh x 14.9p = £394

50% of 2649 x 4.64p = £61

So £455 income, plus what you save on electricity bills which could be around £100. So £555 - not £655 would be more realistic.

You obviously have to take a guess at future inflation rates and Fuel inflation rate.

Also you must consider the lost interest on the £6380 which at, say, 3% is initially £190. That sum will be compounded.

For a fair comparison your inflation linked income/savings(the £555) would also be invested each year

So your first year savings will be in the order of £365.

You can use your own figures for inflation rates, interest rates, fuel inflation rates and in-house usage. However IMO the 7 years payback is just a joke. In fact double that(14 years) would be excellent - again IMO and that is assuming no repairs needed.

Hi Cardew they have quoted near enough £200 savings on electric that`s where the difference lies. The EST use electricity savings @ 25% the suppliers quote bill savings @ 50%. in all three of my quotes
Who is correct?

Martyn1981

Sirlaughalot wrote: »

Hi Cardew they have quoted near enough £200 savings on electric that`s where the difference lies. The EST use electricity savings @ 25% the suppliers quote bill savings @ 50%. in all three of my quotes
Who is correct?

Hiya SL, will try to do some numbers for you.

Firstly leccy savings, forget 50%, I think this is an extremely high figure that hardly anyone will reach, unless they have some sort of daytime demand/business. More average would be around 25% to 35%. However you said that you expected very little use during weekday daytimes, so I’d estimate nearer £80. I think this must be near the bottom possible, as it equates to about 2kWh’s of leccy savings per day, and just baseload savings would probably average around 1kWh/day.

Income/expenditure – I think £6,380 for a 3kWp system is too much, but let’s run those numbers for comparison purposes.

Income streams:
FIT 2,649@14.9p = £395
Export (deemed 50%) 1,324.5@4.64p = £61
Leccy savings estimate = £80
Total £536

Using the same spreadsheet as before with compounded interest @ 3% net, inflation @ 3%, panel degradation @ 0.7% (but no new inverter due to the extended warranty you mentioned), gives a breakeven point at year 13

Savings (£6,380) compounded = £9,369
PV income = £8,005
PV income re-invested and compounded = £9,528

At a net interest rate of 2%, the breakeven point shifts to year 12

Savings (£6,380) compounded = £8,091
PV income = £7,303
PV income re-invested and compounded = £8,119

PV is largely maintenance free, but there is always the chance that some un-warranted part may need work/replacing.

Regarding prices, you will have to haggle I'm afraid. Been looking at on-line quotes, but many are too ambiguous, built around ‘from …’, however found one that gives prices ‘if … within 25 miles (you’re not), if normal scaffolding, and if normal cable run’, then extrapolated from the example 2.5kWp and 2.7kWp systems, to give prices of £5k to £5.5k.

Running the 2% calculation again, but after putting the £1,200 inverter replacement back in in year 12, gives breakeven just after year 10 & then again at year 12 (due to estimated inverter expenditure)

Y10: Savings (£5,500) compounded = £6,704
PV income = £5,944
PV income re-invested and compounded = £6,485

Y12: Savings (£5,500) compounded = £6,975
PV income = £7,303
PV income re-invested and compounded = £6,895

Y20: Savings (£5,500) compounded = £8,173
PV income = £13,503
PV income re-invested and compounded = £14,595
(Plus 45 to 50MWh’s of clean leccy)

Sorry for all the numbers, and of course this is all guesstimated. How’s the headache?

Mart.

Martyn1981

Sirlaughalot wrote: »

The rep said the system would have paid for itself by year 7 end the inverter would be warranted for 20 years. The panels have a 10 year product warranty and a 25 year power output warranty to 80%

Me again (sorry). You need to be careful with these payback figures. They tend to assume high levels of general inflation and/or very high levels of energy price inflation.

Whilst energy prices may rise fast (coal emission regs that came in this year, gas prices rising etc) this won't affect you as much since FITs and export go up with general inflation (which may dilute high energy inflation), and you expect lower leccy savings. These factors will reduce a lot of the 'assumed' energy price increase. That's why I just use a 3% inflation figure, it may be too high or too low, but is probably a fair and reasonable guess, for now.

Mart.

Martyn1981

Sirlaughalot wrote: »

A generall question to all MSE users who have had solar panels installed did any of the energy/fit savings over yr1/yr2 meet the installation companies estimate?

SL

Me, yet again (double sorry) but here's a post from yesterday that you may find interesting:

krispey wrote: »

Only ever lurked here, so after exactly 2 years of production here goes -

1.98kw system, solarworld panels, power one inverter, south facing, NE Engand.

1st year estimate from Installer 1820kwh, Actual Meter Reading 1826kwh (5 July2012)

2nd year estimate 1803kwh Actual Meter Reading 3633.0 Kwh.

So there we go 2 years and within 6Kwh of the estimate given by the installer, the system incidentally has never deviated further away from the estimate at that point in the 2 years of ownership by more than +/-40Kwh at any time in either year.

For these O's people average daily O's of system comes out at 917 O's per year or a daily average of 2.51 O's per day.

Hope you find this useful, will post again in another year.

Year 3 target drops to 1795Kwh so interesting to see the panel decline over the next 12 months.

Mart.

Cardew

Sirlaughalot wrote: »

Hi Cardew they have quoted near enough £200 savings on electric that`s where the difference lies. The EST use electricity savings @ 25% the suppliers quote bill savings @ 50%. in all three of my quotes
Who is correct?

WHICH agreed with the EST, IIRC they talked about £70 pa savings.

Bear in mind that the preferred method of maximising in-house consumption is to divert electricity to an immersion heater.

If you have a hot water tank(and many have combis these days) you saving if you have gas will be at gas price per kWh + boiler efficiency - say around 5p/kWh.

Oil CH about 7p/kWh

If you don't have gas/oil then most would have economy 7 to heat water at around 6p/kWh. Few houses would be all electric without being on Economy 7.

The other trick used by installers to 'inflate' savings is to to use a very high price for electricity.(they appear to use 15.1p/kWh) This price per kWh took into account the Tier1 price, whilst any savings would only be at the lower Tier 2 rate. In fact with the majority of new tariffs having only a daily standing charge option, the savings will be at the one electricity rate.

Martyn's figures are roughly like mine -in fact his savings are slightly lower as he uses £80 pa for savings and I used £100.

It comes back to my original point that 'payback' in 12 or 14 years is realistic. You need to take an extremely long term view to invest in anything that would take such a period to get your money back.