Copyright Mike Hillard

23rd March 2010

[Making electricity from the sun]

One thing to recognize is that not too many people have actually installed PV yet, which does suggest it is not financially exciting without a subsidy.  But as I keep meeting confusion about what ‘Solar’ is, can I make sure we are all in the same place as there are two forms of ‘solar’ (apologies for those who know).  One is solar PV which stands for ‘PhotoVoltaic’ and generates electricity.  ‘Solar Thermal’ on the other hand directly heats your water passing through the tubes.  We are only talking about solar PV here.

So to the question “Is it good?” to which we need a correct answer as we are now going to receive what are called ‘Feed in Tariffs’ for the power we generate from them?  Are we helping the UK and planet earth or not? Govt gets so many things wrong that we cannot assume it works just because they want to subsidise it. There are many vested interests at work in government.

In truth the answer is quite simple but you will decide this for yourselves from the information given here.  Interestingly when I discussed it with the technical director of a glass manufacturer a couple of years ago I proved quite quickly to him that it is a non viable system (hint).  He went very quiet and didn’t argue – after which he told me they had invested heavily in a PV glass production unit – and I didn’t hear from him again.  PV panels do of course produce electricity so what are the issues?

Matching supply and demand through the year

First consider when you use electricity and then when you don’t.  And when the sun is out and when it isn’t.  Not great is it?  Maximum electricity output from PV is almost when we need it least – in fact the only time demand is lower than when PV peaks is through the night in the middle of summer – and is zero when we need it most.  Not exactly a perfect match and precisely what I hope you would not choose if set the task to supply the nation’s power.

Across the year, peak PV production is on 21st June (as long as it is a sunny day) and the trough is on 21st December.  Now when do YOU use power? Let’s consider the chart below which shows 3 things:

  • Our electricity demand through the year
  • Wind generation capacity through the year (indebted to Dr Graham Sinden, Oxford)
  • PV generation capacity through the year

It shouldn’t be a surprise but isn’t ‘Oh Dear’ the right response?  The wind generation plot is the average deduced by Dr Graham Sinden over more than a 20 years period.  So while wind shows an amazing correlation with demand, PV is as far away as possible.

Supply and Demand across a day

But now let’s consider what happens not across a year but across a day, and we will use midsummer (21/6); midwinter (21/12), and the equinoxes (21/3 and 21/9) to demonstrate.  But while doing it, as the Govt has launched its Feed in Tariffs which are designed to encourage all of us to fit PV, we will assume there is enough PV to meet the demand for the day and time it produces its maximum – midsummer in the middle of the day.  The 3 charts are all to the same scale with the same axes so are directly comparable and visually represent the reality.  There is no trickery and I hope you will agree it illustrates the situation rather well.


  • The top plots show national electricity demand (supplied by the National Grid).
  • The curved symmetrical plot underneath shows the very maximum available electricity generated by 32GW of PV units.  It assumes a sunny day from dawn to dusk right across the country.
  • The shape of the PV curve was confirmed with a major Japanese manufacturer’s supply curve.
  • Other generation has to supply the area only vertically striped in black

Midsummer – 21st June

Demand when PV peaked was 33.4GW in 2009, which is the reason the peak PV was chosen as 32GWp (GWp = ‘peak’ power produced by PV units when generating at maximum) leaving almost no other generation needed.  The demand at 10.30pm was 31.7GW but as there is no PV at that time – it all has to come from other sources.

The requirement for all our other generators is now even more volatile as there has to be 32GW available to fill in for very dull days but across the 24 hours this goes up and down extremely fast through the range 0 to 32GW.  And the 33.6GW peak has to be available when the sun doesn’t shine.  AND these figures assume blanket sunshine across the entire UK – not entirely likely – so any sunshine shortfall will again vary the load on the other generators.

Now we cannot cost effectively turn the nuclear reactors on and off, nor can we the coal fired – and the wind cannot be turned off if blowing somewhere, and any tidal or tidal current generation will come when it does. So PV creates mayhem for the rest of the industry unless fitted in insignificant quantities – as now – when it is honestly just ignored as it is insignificant.

And on a wall to wall sunshine day – PV produces just 42% of our total demand on 21/6 even with this 32GW of installation.

The Equinoxes – 21st March and September

The requirement from the rest of our generators is now hugely variable and now in the range 11GW to 49GW.  Without PV the range is 30 to 49GW and even this is hard work but the Grid controllers do a great unseen job.

And on that wall to wall sunshine day (even less likely now) the PV covers 15.6% of demand.

Midwinter – 21st December

Ah!  Sad might be an appropriate observation as this is also with wall to wall sunshine!  The only supply problem is that we now have two peaks each day when the sun is earning its keep.

And with wall to wall sunshine it now provides just 5% of demand through our peak period.  And we still need to cover the peak of nearly 57GW as there is no PV then, PV cannot replace any other generation at all.   It is all ‘add on’ capacity – all 32GW of it in this case.

And just to help you compare them better – here are all three with full sunshine:

So how much power would this lot produce taking the weather into account?

Well, we know how much panels produce on average through the year which takes account of the weather, and this means the 32GW would actually produce less than 20TW.hours – or 5.2% of the annual national demand of 383TW.hrs – and all for £160B assuming £5K/Kwp installed panel cost.  This would be an equivalent capital cost for the national generation capacity of more than £3T OR £3,000,000,000,000. Not sure what you think but that is horrendous as far as I am concerned.

Our Capacity to install PV

While I know we don’t expect to produce all our electricity from PV, it is useful to get a handle on how many installations would be needed to do it (assuming it can be stored), and then we can consider the impact of installing less.  The UK’s annual consumption is 383TW.hrs – or 383,470,000,000KW.hrs.  Now a ‘normal’ 12 panel PV array will produce in southern England about 1,800Kw.hrs a year.  So to produce everything we would need 213,040,000 roof installations of this size – or a lot – and this would require that we store it for use when we need it.  In fact as we only have 23M houses in the UK we would need to cover ALL of them to produce just 10% of our power.  No wonder the glass companies and solar installation businesses love this one.

And fitting all our houses to provide just 10% of our power would cost £300B that we, the public, have to pay for.

But what does that 32GWp require?

Assuming the 8 panel installations which are about 2KWp, we would need 16M installations or 70% of all dwellings in the UK fitted with them to achieve the above.

The capital impact of installing PV

We have already seen that we would need all the conventional power stations and renewables that we have, and that PV simply adds to the capital cost for the UK.  So not a single generating station can be shut down no matter how much PV we generate, and the cost of 32GWp would be at least £160B as most prices I can find are well above the £5K/Kwp.  And given a life of say 25 years (output drops with time) we would need to be spending about £10B each year including fitting costs to keep them going.

So what about the impact on the UK’s cost of electricity!

The ‘Feed in Tariff’ (FiT) for PV electricity is no less than 41.3p/ which is a staggering figure when you think some supply Companies are now selling it for 8.27p.  It is 5 times the market price.  Not 20% more but 400% more.  So every unit pushed into the grid – is increasing the average cost of the Grid buying it – which increases the cost to all consumers, Industrial and Domestic.  And this FiT is said to be ‘guaranteed’ for another staggering 25 years.  So how does the cost of PV electricity and the FiT compare with the alternatives?  The Chart below shows these:

Costing Notes:

  1. A. The cost of PV depends on the purchase price, installation cost, your interest rate, roof direction and pitch – all of which vary enormously.
  2. B. The 38p figure only recovers the capital (purchase price) and assumes £5,000/KWp; 20 year life, and no interest cost [but the average cost is between £6,000 & £8,000 (Energy Savings Trust].
  3. C. Using their average of £7,000 and taking 5% interest and a 25 year life gives 76.0p.
  4. D. Interest at 8% and a 20 year life gives an astonishing £1.08 – but some of us knew we would never fit it as it was always a non player.
  5. E. Paying for PV on a credit card or other expensive credit at say 20% would give £1.51/ and removal of the FiT during the life of the system would be financially dreadful – but it is dreadful anyway. This figure is not included on the chart.
  6. F. Most prices are way above the £5,000 and many are above the EST bracket –I have found one at £12,000.

The ‘first generation’ estimate for wave was about 24p (courtesy Pelamis) and at that time second generation was expected to be around 16p.  Mature technology should be some way below that at maybe 12p and probably lower.

This leaves PV alarmingly higher than anything else dreamt of and costing way more than even the 41.3p FiT.

Interesting? Surely it needs little explanation so why on earth would anybody choose to generate power from the most expensive source and from one that produces very erratically and generally supplies when we don’t want it?  It seems like madness to me so I wait to be convinced otherwise.  And I am sure I will wait. And wait.

But we have also seen that we do not save any generation capacity, so if the existing capital base not only provides a bit less power but has to do so by meeting a much more variable demand, by definition the unit cost of that electricity they do produce will rise.  Seems like a ‘LOSE LOSE’ situation to me.  Except of course for the suppliers.  And the PV suppliers and installers.

But where does the 41.3p come from and go to?

Well, when PV costs what it does to generate you are not going to get many takers unless you pay a huge price, and if Govt wants to be seen to be doing something – anything – then it has to set a price like this, but as you can see it isn’t nearly high enough.

As for who pays, as we are apparently spanning 25 years with the guarantee, there is no doubt it will change during this time but either the Govt must pay from taxation (in which case all taxpayers pay) or it is passed onto the Grid and then to consumers through an increased price for power (in which case all consumers pay).  It is unlikely the poorer members of society will install them, so if the cost of FiT goes onto the cost of power they will yet again suffer. And how much would this 5.2% of our supply cost?  £8.26B/yr!  And everybody loses.

Comparison with wind

As we saw, the supply curve for wind is very similar to our natural demand curve [the first Chart], so it is sensible to compare wind with PV financially as well.  This isn’t the place to compare micro (roof top) wind, which is totally different, but shouldn’t we compare commercial wind generation with PV?  Here are some figures to think about:

3MW Commercial

Wind Turbine


Capital Cost per KW of generator


£4,800/[£12, 5001]

Power generated/yr per KW of generator



Power generated/yr per £ invested



Collector efficiency

28 to 33%2


To produce 7,300 MW.hrs/year

1 turbine

4,050 x 12 panel houses

To produce to 20TW.hrs

2,666 turbines

17M house roofs

Capital cost for the 20TW.hrs



PV doesn’t make any sense at all does it!

1 The trade clearly expects a lot of new installations, so the world and his wife seem to be trying to get in on the act.  The price span is therefore huge.  As with fluorescent lamps, I am sure the quality is varying hugely, but cannot prove it.

2 The ‘efficiency’ of a wind turbine is its output divided by what it could produce at maximum continuous output.  Offshore is higher than onshore, but sites are chosen that conventionally produce more than 28% efficiency.  This is often used by those who argue against it as a huge negative.  Measuring PV in the same way gives it about 7.1% efficiency.  Interesting to find those happy with PV but not with wind because of production variability.


  • Fitting PV will not be giving you a green flag over your property.  It isn’t actually green at all, but we will in further articles analyse energy that is.
  • Discovering the carbon footprint for a PV panel is extremely difficult to estimate and the manufacturers don’t supply this information, but early figures were horrible since when I trust they have improved a bit. But several years is taken to recover the carbon alone (best information).  So there is a lot of carbon emitted in making, supplying and installing them, whereas with wind the carbon cost is recovered in many months and nearly always in less than a year depending on the installation.   Offshore takes longer than onshore.
  • As the conventional generators have to be available for peak demand, the fact that PV generates where the power can be used is not really helpful as the Grid will have to carry the whole load it does now.  Locally produced power is called ‘Distributed’, and generally this is considerably more efficient as it doesn’t have to be transported during which process up to 10% of it is ‘lost’.  So locally generated wind, biogas, incineration, hydro and even gas are more efficient than national generation.
  • In the same way, the Grid will have to be able to carry the whole load so cannot be downgraded as other distributed generation allows.
  • We could ask how the Govt came to reach their conclusion as I have not magiced these figures out of thin air.  The basic data is available to anybody with a mind to find it.  It seems likely they felt the need to do something and didn’t know what else to do – plus we can expect there was a lot of lobbying for PV.


  1. 1. For PV to be viable with the 41.3p FiT we can work out exactly how much you should pay for it in the first place. Assuming 5% interest rate and a 20 year life the answer is £3,300 per Kwp but this assumes the 41.3p will be paid for the next 20 years – something I am certain cannot happen.  I think it impossible for this situation to last for long, so note 2 below is surely the base line we should work of, but the above sorts the wood from the trees for the current situation.
  2. 2. If the FiT for PV was double the cost of wind and about the same as Tidal or biogas, then it would be 6.6p – and that might be reasonable.  However this means the maximum you could pay for the PV would be £520per Kwp.  Now as you can see some suppliers are asking £12,000 per Kwp – there is more than some way to go reducing the cost of production.  And no matter how much production is encouraged by subsidy (which is what the FiT is) it hasn’t much chance in anything like the near future in reaching these figures.  It requires a dramatic step change in the science to do it and it will always produce the power when in the UK we don’t need it.

Solar PV makes no sense to promote or even to install UNLESS you can store the power and go off grid – so you don’t use any conventional mains power.  If YOU can personally live with both the supply problem and the cost that is fine.  Otherwise it will be a burden on society and as so often those who are seriously trying to help the environment (and don’t mind unselfishly investing to do that) find they have not helped at all.

I have two absolute requirements for energy decisions: we need the very best bang for every buck we spend; and don’t invest in saving or producing energy unless it is the lowest cost way of doing it.  Better to generate from wind or tide at those prices than save a few KW.hrs costing a small fortune.  It is for this reason that defining Zero Carbon houses as only those that can generate sufficient on site power so they supply to the grid what they take from it – is hopelessly expensive and ineffective.  It is another of those decisions that is illogical and presumably the result of a lot of lobbying.

The FiT needs to be stopped with great haste, as committing to 25 years of that will be awful.  At least when the public have been advised the real situation, they cannot argue if the FiT is removed very soon and during the 25 years they thought it was guaranteed for.

A Parting Thought.  Wind turbines are often opposed on the grounds of erratic supply, but it can be seen that not only is PV hugely more erratic but it produces at the wrong time and at huge expense.  Strangely I have never heard PV objected to on the grounds of variability.  I wonder why?

This is part of a series of articles that will explain, from a totally independent perspective, the reality of most of the generic eco products or green energy products in the market.  There is much confusion in the minds of most of the interested public which needs to be resolved.

Subjects being covered will include micro wind, commercial scale wind, ground and air source heat pumps, biofuel including wood pellets, wood stoves, solar hot water, multifoil insulation, rainwater harvesting, biodiesel, palm oil and condensing boilers.

When lecturing in a certain location (which I will not name) I was ‘asked’ not to put the reality as I had been doing.  I asked if I was being shackled and as the answer was effectively ‘Yes’ I withdrew instantly and declined to take further part as I will only give the truth as I see it or know it.  I will not be party to anything but independent advice.

Along with this series will be articles explaining similarly how an affordable, viable, zero carbon Britain can be achieved.  We need to know what to spend our capital on as well as what not to.

A further series will cover climate change from a perspective you will not have seen before.  It will hopefully lead to conclusions on not just the possible reality of climate change but will also lead to quantification of the temperature rise we may have to cope with and the impact on us of that rise.