My solar PV first year payback calculation

Cardew

Mcfi5dhc wrote: »

Well lets build it then!

Could some Solar-Sceptics please provide some info they would like to go into to it? For example, if the £7500 was in savings accounts, what long term rate would they get? Would they pay tax on it? Are we assuming they are dipping into it every month or quarter to pay their electric bill? If not, we need to assume they are paying the bill by some other means. So therefore, how much would actually get compounded (if any!)

I'll quite happily do 50 spreadsheets, but I think we need an agreed base to start off with.

M

Not sure I understand what you mean by dipping into the £7500.

The maths is quite simple to my mind.

You invest £7,500 at 5% gross, 4% nett so get £300 pa compounded. i.e. you leave the £300 nett interest in the investment and next year you get interest on £7,800 i.e. £312. Next year you have £8,112 invested etc etc.

If you use, say, 5,000kWh electricity a year, you still use 5,000kWh per year regardless of a having a PV array or not.

With the PV array, you now get some free electricity and the government pay you for the electricity produced.

The economic equation is to compare the savings/income from the PV array against the loss of interest on the capital invested.

P.S.
Incidentally the term 'solar sceptic' seems to imply that we have something against solar energy. Nothing, in my case could be further from the truth. We are simply making the point that in our opinion the present cost of the technology does not make it a viable financial proposition. Solar hot water is a joke in financial terms, but certainly solar electricity generation is a better proposition with the new Government subsidies - but still IMO not there yet!

In no way are we making a criticism of those who wish to fit any form of solar.

bmbyker

albyota wrote: »

I have used the thanks button a number of times within this thread for some great info and advice, it is such a shame there isn't a 'sodoffgetalife' button for the sceptics, I too have ASHP, RWH, and am currently looking into the PV panels and I agree with the vision of energy costs rising year on year, which will shorten the ROI on PV or ASHP boilers (350% efficient), and most certainly HIPS will push the property into A rated therefore should sell easily, all this while people running round seeing if they can max out their gas boiler to 91.5% efficiency.........come on! well done bmbyker and
Mcfidhc well done.

Albyota.

As we both have similar installations one of the intagibles that you can only get from having the systems is that we feel the PV is offsetting the cost to run ASHP as well as the house. I checked our usage of electricity last year. We were using on average 22 units a day. Now we are using 20.74 according to the spreadhsheet (1 months figures) but we have the ASHP running for about 3 hrs per day. But the beautiful number is last years daily gas usage, 11 therms a day - now less than 0.1 therms. During the winter months it was 135 therms and we ran the house at 16c last winter! I await this winter with interest. I have a long term goal to offset as many energy costs as I can. My income is 'fixed' as I am a pensioner, although not retired. Nobody came to my door and sold this to me, I wasn't canvassed. I spent a lot of time on the web (which is my playground) and took all views into account. One other point, I would also like that 'button'.

Finally, I say to you go for the PV, you will see another drop in energy usage and if you can cost it so that you can install without the grant but get it for less that a grant assisted company would charge that would be a complete bonus. :T

Cardew

bmbyker wrote: »

Albyota.

As we both have similar installations one of the intagibles that you can only get from having the systems is that we feel the PV is offsetting the cost to run ASHP as well as the house. I checked our usage of electricity last year. We were using on average 22 units a day. Now we are using 20.74 according to the spreadhsheet (1 months figures) but we have the ASHP running for about 3 hrs per day. But the beautiful number is last years daily gas usage, 11 therms a day - now less than 0.1 therms. During the winter months it was 135 therms and we ran the house at 16c last winter! I await this winter with interest. I have a long term goal to offset as many energy costs as I can. My income is 'fixed' as I am a pensioner, although not retired. Nobody came to my door and sold this to me, I wasn't canvassed. I spent a lot of time on the web (which is my playground) and took all views into account. One other point, I would also like that 'button'.

Finally, I say to you go for the PV, you will see another drop in energy usage and if you can cost it so that you can install without the grant but get it for less that a grant assisted company would charge that would be a complete bonus. :T

bmbyker,

Surely the fact the you have installed the admirable ASHP system is irrelevant to this discussion on Soar PV.

If the system saves you money against gas heating(which in itself is debatable) then it will save you money even if you had no solar energy and your electricity was supplied as normal.

Incidentally why do you also 'want that button'? (to silence the 'solar sceptics')

This is a discussion forum on the merits/demerits of 'green' energy - in this case solar energy.

Can you not tolerate any counter view on the economics of fitting solar? Or do you want the thread to be a series of self-congratulatory posts?

albyota

OK. I appologise for the button comment, it was late, I was tired, blah, blah blah, before I do go and install a PV array could someone actually work out the whole ROI payback debate including volatile future interest rates, interest Tax, etc... along with projected electricity and gas increases, and possible but increasingly likely the government/DECC domestic £200 Carbon Tax Levy...as this will mess up all the figures...

Cardew

albyota wrote: »

OK. I appologise for the button comment, it was late, I was tired, blah, blah blah, before I do go and install a PV array could someone actually work out the whole ROI payback debate including volatile future interest rates, interest Tax, etc... along with projected electricity and gas increases, and possible but increasingly likely the government/DECC domestic £200 Carbon Tax Levy...as this will mess up all the figures...

Well of course you would need a crystal ball to be able to give accurate figures as there are too many unknowns.

I think we can all agree that solar hot water is a non-starter in economic terms??? so let us consider solar PV

For future installations, would the following be reasonable assumptions?

Cost to install - £7500?

interest rates - 5% gross?

Annual output - 1000kWh?

predicted future fuel price inflation 5%?

Maintenance/cleaning?

I can't think that the Government's possible carbon tax is a factor unless your property is totally self sufficient?

Antispam

Did any one see Coast the other night about Norway

They use very little gas must of there energy comes from hydro, they send 1/3rd of there gas to us and have at least 40 years left. They are developing ways to capture energy through salt water and fresh water bonding them together and be held apart, its called osmotic power or pressure !!!!!! osmosis

http://bluelivingideas.com/topics/saltwater/saltwater-freshwater-blue-energy/

albyota

Cardew, this is a start,

Cardew wrote: »

Well of course you would need a crystal ball to be able to give accurate figures as there are too many unknowns.

I think we can all agree that solar hot water is a non-starter in economic terms??? so let us consider solar PV

For future installations, would the following be reasonable assumptions?

Cost to install - £7500?............ £421 for each 185 Watt panel, 10 required to ensure economical sense, plus £3300 for the scaffold tower, installation, brackets, DC inverter, 2 way meter & grid connection, labour, commissioning. + 5% VAT


interest rates - 5% gross?...... if thats what it is, sustainable over 10 years?

Annual output - 1000kWh?.......1850W array would yield after losses about 1500 kWh (conservative estimate)

predicted future fuel price inflation 5%?.....If the big six can put the price up by 40 -50% last year, and have just announced a 10 ish % decrease just to help with the economy (but causing chaos with capped /fixed and penalties if you move) you could estimate 5 - 10% inflation or MORE.. if they are pressured by Mr Brown/Cameron for ‘Dirty’ fossil fuel, CO2 emissions, CRC (climate reduction commitment) big fines, penalties.

Maintenance/cleaning?.........my solar thermal panels have been on my roof 3 years now, I have never cleaned them, it is the same glass covering as PV uses, they get dusty, bird doo, but rain is not in short supply on average every 24 days, there is no maintenance, as there are no moving parts, at most you would have an annual check on the electrical terminations, and calibration test if this is chargeable you could factor in £65 per year.

I can't think that the Government's possible carbon tax is a factor unless your property is totally self sufficient?

.......

http://www.dailymail.co.uk/news/article-1142710/Millions-face-stealth-tax-heating-bills-subsidise-green-energy.html

‘The green levy, or 'Renewable Heating Incentive', is part of an energy package to be unveiled today by the Energy and Climate Secretary Ed Miliband.
As well as grants for domestic windmills and solar panels, he will announce plans to insulate seven million homes.
The measures will be funded by the levy on fossil fuel energy suppliers - which will be passed on to us in our household bills.’

Mcfi5dhc

The first attempt at the spreadsheet is ready!

Please PM me your email address, and I will try and send it ASAP.

PLEASE NOTE: This is a 1st version - it may need tweaking. Please don't post abuse. Please do post constructive criticism.

All the assumptions are changeable, but I have used:
Units Used 3870
Units Generated 1186
Cost per unit 10
Annual unit increase 5.00%
Interest on Savings 4.00%
Initial Investment £5,450
Maintenance (annual) £50
Asset Loss 5%

You can fiddle with it as you wish.

M

albyota

Don't forget the Feed in Tarriffs from april 2010 of 36.5p per unit generated whether it is used in the house or not!

Mcfi5dhc

The 36.5p is included as a fixed number ( as it won't change), and just multiplies your generated units by 36.5p. Thanks

All other numbers quoted by other people are either in the spreadsheet, or are easy to change variables