First year figures

Having finally had a chance to sit down and do some calculations on our first year with solar power, the figures are quite interesting.

Based on our use over the previous two years our average annual electricity consumption was 4320 kWh. Our first years solar generation was 4047 kWh which is around 93.5% of our average usage. This is much better than we expected, we had hoped for 75-80%. It seems that with a bit more effort to improve efficiency and reduce waste we could get very close to 100%.

The electricity consumption figures for the first full year with solar show that we used 2720 kWh. This is around 63% of the average for the previous two years and gave us a saving of around 1600 kWh. This works out at around £190 saving on our annual electricity bill at current prices. Adding this to the income from the FIT we made a net return of around 14% on the installation cost. This means the pay back time will be just over 7 years.

Overall this is on the high side of our expectations and we are very pleased with it. Given the very indifferent summer we had in 2012 it will be interesting to see how the system performs in future years. The majority of the electricity the system generates is in the 6 months between April and September. If we have a better summer then the likelihood is that the annual generation will exceed this years figure and take us close to the 100% mark for generation vs consumption.

Our first year of Solar

We have just passed the one year mark since our solar PV system was installed so its a good time to report on how the system has performed. Before having solar PV installed I looked at various calculators and modelers to see what sort of yield we could expect. This allowed us to calculate the expected return on our outlay and how long it would take to pay for itself. The EU has a calculator that uses satellite data to predict sunshine amounts for locations in the UK and most of  Europe which I used. This reported that our system should generate around 3640 kWh in a year. In fact we generated 4047 kWh in the year, around 11% above this figure which was very pleasing. This was despite the summer being rather poor.

This electricity generated equates to earnings from FIT revenue of around £1870. I have estimated that savings on our electricity bill will be at least £200, although the final figure could be quite a bit more. In total this gives us around £2075 which is just over 14% of our capital outlay. If the system continues to perform this well then we can expect it to pay off the capital cost in around 7 years.

There is a link to the EU solar PV modeler on my useful links page and there are also a number of other useful calculators included there. These are well worth a look if you are considering installing Solar PV as they give a reasonable idea of the likely returns possible. The cost of installing Solar PV systems has come down quite significantly in the last year so there are still opportunities to get a reasonable return if you have a suitable location.

It seems our solar panels have proved attractive to the local bird life as well as a family of pigeons seemed to have taken up residence on our roof over the summer. I need to get the ladder out and have a look when there is a suitable day. I doubt they will do any harm apart from blocking the gutters with nesting material but I will take a look to be sure.

Solar powered kiln update

Items that have just been glaze fired

We have used the kiln several times over the course of the summer for both bisque and glaze firing and have been very pleased with the results so far. The biggest challenge has been finding reliable sunny days to fire the kiln so we can stick to our green agenda. With careful timing of the firing it has been possible to have the main part of the firing (when the kiln runs at full power) happen when the solar panels are generating maximum power so that it runs entirely from solar power.

A typical glaze firing has been started at around 7:30am and the kiln runs at 180C/hour until it reaches 600C, usually around 10:45. At this point the kiln goes to full power until it reaches the target temperature which is 1240-1260C, it then holds this temperature for 10-20 minutes to allow the glaze to melt evenly. The firing usually completes some time between 1:30pm and 2pm. As our solar panels face south east we generate maximum power from mid morning to early afternoon which covers the maximum demand from the kiln nicely.

During the early part of the firing when the kiln is gradually warming up to 600C it uses a "duty cycle" which means the elements are turned on for a few seconds at a time. The kiln controller turns the elements on for long enough each minute to meet the meet the requested temperature rise needed, in this case 180C/hour. This is in fact quite gradual, much slower than a normal domestic oven. The down side is that when the elements are on they will draw full power (3kW) which is more than our solar panels will be generating at that time. However when you calculate the power used during this period it is small compared to the amount used in the second part of the firing when the kiln runs at 3kW for more than 3 hours continuously. Our solar panels gradually increase output during the first part of the firing so quit a lot of the energy required will still be supplied by the solar panels. Each firing is in practice costing is very little, just a few pence at most.

The challenge as we head into autumn is to find enough time to cover the kiln firing as the peak power from the panels gradually reduces from 3.6kW we get during the summer. Judging from the measurements I took last year the latest that we will have enough of a window to cover the main part of the kiln firing is probably around mid October. Our plan is to put the kiln somewhere dry for storage over the winter and not fire it again until the spring. At the moment the kiln is in the middle of the garage and we want to put the car in there during the winter months so that is another reason not to fire it during the winter.

We will be busy getting some more work through the kiln over the next few weeks whilst we can, I will post some more photos of work fired in the kiln soon.

Our first kiln firing

Well we finally managed to fire the kiln after waiting for a suitable sunny day, this was no easy thing with the poor weather we have been having this summer. Here are some photos of the work just after opening the kiln the next morning once it had cooled off. The models are my wife's work and the bowls and cups are mainly mine.

Pieces waiting to be removed from the kiln after firing

Pieces safely removed and ready for decoration / glazing

The day we chose turned out not to be quite as sunny as forecast! - well it is England in the summer so we shouldn't have expected unbroken sunshine :-) Despite this we only used about 50p of electricity whilst the kiln was being fired and some of this was down to boiling the kettle and running other household appliances so the actual cost of running the kiln was a bit less than 50p which was pleasing.

We have since done another couple of bisque firings with similar results, we are still waiting for the elusive sunny days of summer when we might fire the kiln for almost nothing!

The next firing will be a stoneware glaze firing which requires a higher temperature to be reached, 1240C rather than 950C. This will use more electricity as the kiln will need to run at full power for at least a couple of hours to reach 1240C and then this temperature needs to be held for a 20 minute "soak" to allow the glaze to melt evenly. I will report back on how this went, we are excited to see the first finished pieces that we made in our own kiln.

Solar powered ceramics

We have been doing ceramics evening classes for the last three years and had been considering getting a small kiln for some time so that we could fire work at home. We had been put off by both the start up cost and the potential running costs. Some research revealed that we could get a hobby kiln that would run from a standard household 13amp socket and had a peak rating of 3kW. I did some calculations about firing schedules and realised that on sunny days between April and September it would be possible to fire the kiln pretty much entirely from the solar power. It would need the kiln to be started first thing in the morning so that the peak load coincided with peak output of the solar panels. Our system generates more than 3.5kW during the middle of the day at this time of year (if it is sunny) which is more than enough.With the summer months coming up we decided to go for it and have now purchased the kiln below.

Our shiny new kiln !

The next step is to do a test firing of the kiln, the only problem is it hasn't stopped raining for the last three weeks and the few sunny days have been during the week.  I did give the kiln a very short run up to check that everything was in working order, the picture below shows the kiln controller in action.

The kiln controller during a short test

We are busy making some work so that we have something to fire once the test firing has been done. The test firing is recommended for the new kiln as the elements will burn off their protective coating and the kiln will have had a "burn in". The test firing involves heating the kiln up at  a rate of 150C/hour until it reaches a temperature of 600C at this point it will be heated up at full power until it reaches the target temperature of 1050C. The test firing should take around 6 hours so I am planning to start the kiln at around 8am one morning as soon as we get a suitable sunny day.

The longest firing we will are likely to need is when we glaze stoneware which requires a top temperature of 1240C, this requires an initial rate of 180c/hour until it reaches 500C and then at full power until the target temperature. This should take somewhere between 6 and 7 hours to complete so the 8am start should still be fine. I might have to start the kiln a little earlier when the days get shorter in late August and September.

I will post some more reports once we have had a chance to fire the kiln for real, this should be in the next couple of weeks. I am going to check how much power we draw from the grid during the firing by taking meter readings before and after the firing, hopefully it won't be much.

We need to work hard now to create some work to be fired but that is the fun bit !

Mystery sounds - solved ?

We had noticed that under certain conditions we would get some odd rattling sounds from the roof, this only started after the solar panels were installed so we knew it was something to do with them and was rather worrying as it seemed something was loose. The sounds only happened when there was a strong wind blowing from a south or south-east direction which is quite unusual so this has only happened about three times since the panels went up.

I contacted our supplier (EVO energy) after a stormy day in February when the sound was very apparent and they said they would send someone to inspect. The earliest day available was in early March so we booked that up and waited. I re-confirmed the appointment a few days before and they asked if we had scaffolding still up, we of course hadn't as the system had been up for nearly 6 months. The day before the inspection was due some contractors turned up an erected scaffolding, I was a bit surprised.

Scaffold goes up again !

On the day a team of three turned up first thing at 8am and took a good look at the installation. After about 30 mins one of them team came down and explained that the tiles and mountings were very secure and couldn't be the cause of the sound. They suspected that the cable runs were the cause as the slack cable had been laid on the tiles between the panels. I went up and took a look and it was easy to see how the loops of cable could be whipped up by the wind and hit the panels, mountings and tiles. A quick experiment flicking the loose cable against the panels was able to produce a metallic sound something like that we had heard - mystery solved maybe?

The team then removed the bottom row of tiles and cable tied all of the loose cable runs to the mounting rails so that they couldn't flap around any more. They were finished and on there way by around 9:30am. Only time will tell if this was the cause, we will listen carefully next time there is a strong south or south-easterly wind.

Having the scaffolding in place did allow me to take a close look at the condition of the panels and see if they needed cleaning. They were not that dirty but there was a thin film of grime from the damp winter months and some residue from bird droppings, we get rather a lot of resident seagulls in the winter ! I took a bucket of soapy water and a telescopic window cleaner with me and gave the panels a wipe over to see how much effect this would have. It did remove a fair bit of grime so I guess it will make some improvement, I am wondering how easy it will be to clean them without the scaffolding. We have a garage with a flat roof on that side of the house so access is quite easy and relatively safe so I will probably give them a wipe over a couple of times a year.

Panels still looked quite clean after 6 months in place

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Winter quarter savings

I have now had a chance to sit down and calculate how much energy we saved from our winter quarter electricity bill. The bills for this quarter over the last three years have been very similar averaging around 1240 units so any saving was going to be quite easy to see. The bill shows that our usage this year was just 780 units which is around 63% of the previous years - very impressive. This amounts to a saving of around £55 on our bill, I have already arranged for our monthly electricity payment to be reduced significantly on the basis of this.

We have made a very big effort to make use of the solar generated electricity, my wife has been doing everything possible to use power hungry devices during the daytime. We used to run the dishwasher in the evening or overnight but this and the laundry, vacuum cleaner are now used during the daytime. In the winter it has also been possible to use the electricity to cook meals during the daytime. Stews and casseroles need cooking slowly over a few hours so they are excellent to cook during the day and then warm up for dinner.

The longer days will give us even more opportunity to make use of our own electricity. I am looking forward with interest on how the system will perform during the summer months. We had the system installed at the autumn equinox so we have only seen how it works on the shorter winter days, the next 6 months will show us just what the system is capable of.

The first FIT payment arrives !

We finally received the FIT payment from our electricity supplier (SSE) on the 31 January, exactly one month after submitting our meter reading. Not too bad given the stories that are circulating about other suppliers and the need to chase them for payment. The amount was just over £300 although this did include the last 10 days of September which were not strictly part of this quarter and accounted for around £60 of the total. Our FIT registration hadn't been processed in time for them to pay this in the previous quarter.

I am still waiting for our electricity bill for the winter quarter, the meter reading was submitted last week but they usually send the bill out in the first week of February. Once I have this I can make an estimate of how much our electricity bill has been reduced. The number of units used during this quarter over the last three years are very similar so any difference will almost certainly be down to using our own electricity.The meter reading indicated it would be something like one third less than previous years. Of course it would have been much easier to measure how much we had saved if we had an export meter.

I will post a summary of the earnings + savings for the quarter once the bill arrives.

Good news is that February has started very sunny if rather cold, the sunshine is at least some compensation for the cold weather.

FIT payment is finally on it's way

We finally had a response from our electricity supplier to confirm that they had processed our first meter reading and we would be receiving our FIT payment soon - hurrah ! We have also just had the first full quarters electricity bill since the system was installed, this looks very promising. We have only used around 65% of the electricity compared with the same quarter over the previous three years. This would mean a saving of at least £50 on our electricity bill this quarter and should mean a saving of around £200 over the full year. I will calculate the exact figures once I receive the FIT statement which should arrive in the next week.

I have just updated the statistics page and added a couple more useful links - take a look !

Back soon with some more accurate figures once our FIT payment arrives and we have our electricity bill.

Our first quarter

The end of the year meant that it was time to submit our first quarterly meter reading to our electricity supplier and then wait for our first payment to arrive. This is where the system finally starts to pay us back in a tangible way, the meter reading on the 31 December was 679 units which should work out at just over £300. The website said rather gloomily that payments may take up to 65 working days, if that is true then we may well be submitting our next reading before getting paid for this one. I will post an update when payment arrives and I can say how long they actually took, reports of other suppliers taking months and needing to be chased doesn't bode well.

The other part of the equation that we are currently missing is how much of our own electricity have we been able to use as this will result in savings on our bill. There is an assumption by our supplier that we will use 50% and export 50% but this seems hard to believe. When the sun is out the system generates something between 1 and 3 kW during the day. The household devices that are always on like the fridge etc. only consume a total of 200-300W so unless we are running the dishwasher, laundry, vacuum cleaner or other high power devices we are only likely to be consuming 10-25%. I have am going to compare the electricity usage this year with the previous two or three years and see how much less we are using and try and calculate the savings. This will probably take a full years worth of reading before we will get a clear picture.

Another thing worth exploring is getting an export meter installed by our supplier. This will not only tell us how much electricity we export but also allow us to calculate exactly how much we have used. I am guessing that we will probably export something like 70% or more so it would enable us to get paid for anything more than the 50% estimate. It only comes to 3p a unit but it would still be nice to have.

We are now looking forward to 2012 and the longer days of spring, its going to be very interesting to see just how well the system does in prime months from April to September when it should really start to pay us back.

A happy 2012 to everyone.

The last minute rush

Perhaps not surprisingly there has been a last minute rush to get systems installed before the 12 December deadline to qualify for the current FIT rates. In our own immediate neighbourhood there are at least another three systems that have gone up, the installers were working on Saturday and Sunday last weekend.  A neighbour of ours who had been thinking about installing a system had their system put up on Saturday. I just hope she can get her application in and accepted on time - fingers crossed for her.

Our own system has been doing nicely since the weather got a bit brighter in mid November, we just managed to achieve the predicted yield for November and seem to be doing very well so far in December. Our generation meter has just passed the 600kWh mark. I am regularly updating the information on my daily statistics page so do take a look at them if you are interested in how the system is doing.

I am still unsure how much of the energy generated we manage to use ourselves, we will probably only find out when the next quarters bill turns up and I can compare with last year. It seems likely that we are probably  using most of it at the moment as it is only a few hundred watts on the cloudy days and the PC, central heating pump and fridge  will probably consume that amount.

Keeping up with neighbours

We took the dogs for a walk around the neighbourhood on Saturday and counted how many houses now have solar panels, there are now nine on our regular route. It seems that once one house has installed panels others nearby have quickly followed suit. My wife took  photos of some of the systems, it's quite interesting how different each system is. These are all within half a kilometre of our house.

   The house on the left was the first to install panels in late spring and was followed by the neighbour on the right a few weeks later.

They were followed a few weeks later by their neighbour and in the last couple of weeks the next house along has installed an identical looking system, the scaffolding is still to be taken down.

A little further down the road another house had a system installed in the last two weeks.

A bit further down the road and another house had a system installed in the last week.

With the reduction in the feed in tariff rates due in the next three weeks it will be interesting to see how many more appear before the deadline.

Changes to FIT scheme

There was a rather sudden and unexpected change to the UK FIT scheme announced on 31 October. A review of the scheme was taking place and an announcement on changes of the rates paid was expected. The big shock was both the amount that the rate was to be cut and how soon the cut would be applied. The scheme was expected to apply the new rates from April 2012 but they were applied from the 12 December. The cut was also much larger than had been predicted with the amount paid per unit falling to 21p from the current 43.1p.

This has had the effect of causing a rush to have systems installed in time to claim the current higher rate with most installers quickly having all available slots booked up. What will happen after the 12 December is the big concern, it seems these companies will see their work dry up with inevitable consequences.

One of our friends was caught out by this as she was interested in getting a system installed but had not seen the need to do anything in a rush. All of a sudden there was no time to make a considered decision, should she jump at an offer that might not be ideal or accept that she had missed out. It seems very unsatisfactory for both installers and customers.

How solar power works

It might sound simple enough to turn sunlight into electricity but there is a lot more to a Solar PV system than you might first think. Here is my quick not too technical guide to Solar PV.

Solar panels generate DC electricity something like a battery cell hence them being called solar cells or solar batteries. The panels will typically generate 40-50V each and are wired in series as "strings". An array of 12 to 16 panels will usually be split into two even sized strings which are then connected to an inverter. The inverter takes the DC electricity and converts to AC at the correct line voltage to feed into your house mains supply. The reason for splitting the array into strings is two fold,  first it keeps the DC voltage at a suitable level for the inverter to work efficiently with, typically between 200 and 400V. Second there is also the chance that should one panel have a fault you will only lose half of your system, only the string with the faulty cell would cease to work.

In practice the inverter does quite a lot more than just do the DC to AC conversion. Most home Solar PV systems are "on-grid" which means that they are permanently connected to the grid, this is necessary for you to export electricity and earn money for it. For the system to work the inverter has to sense that the grid is up and then synchronise to the voltage and phase of the grid when it generates electricity. If the grid goes away it shuts down and stops generating. Most prospective owners dream that they can be self sufficient in electricity to some degree at least when it is sunny, sadly this is not the case.

I hope this simple description helps to shed some light on how the systems work, there are quite a few good technical articles available which go into the full details of how systems work which you can find with a bit of Googling.

Just a quick update on how our system is doing this month. We are currently well behind the predicted yield due to two weeks of almost unbroken grey cloud. Today was only the second really sunny day of the month, and we managed to generate 9.5kWh. The total for the whole month so far is only 41.6kWh, we are going to need  a decent run of sunny days for the rest of the month to get anywhere near the predicted yield.

In the next post I will discuss the changes to the FIT after the 12 December.

So how much does it earn ?

Probably the most obvious question is how much can you earn from Solar power ?

In the UK the government introduced a feed in tarrif scheme (FIT) for renewable energy generation. When we signed up for the scheme we were guaranteed a payment of 43.1p for every unit (kWh) of electricity we generate. This was paid even if we used all of the electricity ourselves. In addition our electricity supplier will pay us 3p for every unit we export to the grid. As we don't have an export meter they assume that we export 50% of the electricity generated. This means that in practice we will be given 44.6p for every unit we generate. Using this it is quite simple to calculate the revenue from our system. We had the system for the last 10 days in  September and it generated 145 units which earned us  around £64. In October we generated 307 units which earned us around £137.

The unknown factor is how much of the solar power generated did we use ourselves, this would gives us a direct saving on our electricity bill and so should also be counted in any calculation. We are about to be billed for electricty for the quarter ending at the beginning of November so I have used this meter reading to see how it compares with the same period last year. It showed a drop in electricity use of around 200 units, this would equate to a saving of around £28 assuming a cost of 14p/unit. We can't be sure that all of the saving is due to the use of our own solar power but a significant amount must be. We will get a better idea once we have a couple more quarters of bills to compare.

In the mean-time its just nice to be saving something on our electricity bills and also to be generating some income at the same time.

More about the feed in tarrif scheme as the goverment announced the result of a fast track review of the scheme on October 31. It was not good news for people who were still thinking about installing solar power as the tarrifs were being cut by more than 50%. This certainly changes the equations with regard to return on investment. We are hoping our system will pay pack the capital we invested in around 8 years, possibly a bit sooner if it continues to do as well as it has been. With the new tarrif rates it will take a lot longer, probably between 12 and 15 years. I do wonder how many people will want to plan that far ahead. We had doubts about making a commitment to a system that may not pay back for 8 years.

Enough ramblings for today, I will describe how solar PV systems work in my next post.

Proof of the pudding

On paper the system looked impressive but our interest was in how much power it would generate in practice. Every location is different so there is no sure way to predict just how well it is going to work. The PVGIS site has a modeller that allows you to get a prediction of what sort of power your system should generate. Comparing the power your system generates against these predictions is a good way to see how well your system is doing.

Our system was installed on the 20 September so we only had 10 days of data for September to look at. The prediction for the whole of September was 338kWh so one third of that would be 112kWh, in fact we managed to generate 145kWh which was a very encouraging start. We have just had our first full month of data for October. The prediction was that we would generate 217kWh, in practice we managed an impressive 307kWh. This was over 40% more than expected. I think that we were lucky in that the weather for the last 10 days of September and the first three weeks of October was unusually sunny, we will have to see how we get on in the coming months. The last week of October was rather cloudy and the first week of November has continued in a similar vein so we may struggle to do as well this month. I will report on how we did in early December.

Our system

We had our system installed on the 20 September by EVO energy. The team from EVO energy arrived at 8am and were up on the roof working before 9am, the scaffolding had gone up a few days earlier.  The work was quite noisy but progress was good. Two of the team installed the rails on the roof whilst a third one worked in the garage on the inverter and cabling. An electrician arrived to connect the system into the house mains supply which involved a power cut whilst cables were re-routed. By mid afternoon the panels were on the roof and system was ready to be commissioned. We could finally start generating our own electricity, sadly the sun had just disappeared behind a blanket of cloud so we were only generating a modest 500W, we would have to wait another day to see what the system was capable of.


Our roof faces south east and we have 16 Sanyo HIT-N240SE10 panels with a peak rating of 240W each giving a peak system output of 3.84kW.

The inverter and panels waiting to be installed

The rails and panels being installed

The panels immediately after the system was installed.

As you can see the panels cover most of the roof area. We selected the Sanyo panels as they are some of the most efficient on the market. Each panel is signifcantly smaller than equivalent 240W panels from other manufacturers meaning that we could just fit 16 onto our roof. Had we opted for cheaper panels we could only have managed to fit 12 onto our roof. This would have left us with a system with a peak capacity of around 3kW which was less than we wanted.

Useful Resources

Whilst doing research about solar power for our own system I found quite a few good sites for learning about solar power systems and for calculating predicted performance. Here are the most useful ones, all are worth a look -

The EU solar PV calculator - A useful resource for estimating how much energy your own system can be expected to produce.

Solar guide - Lots of useful information and a neat calculator to estimate income.

Solar Power portal - Industry news and resources

Microgeneration Certificate Scheme (MCS) - information about the MCS 

Ofgem - Feed in Tarrif information

The energy saving trust - Information about the Feed In Tarrif scheme and other renewal energy information


Suppliers we got quotes from -
EVO energy
The green home company


Manufacturers websites -
Sanyo solar
Kaco

Taking the plunge

After much research and calculation we finally decided to take the plunge and invest in a solar PV system for our house. With very low interest available on savings and ever rising fuel bills it seemed like the perfect opportunity to invest in something that would both generate income and reduce our electricity bills at the same time. 

Having made the decision to invest in solar power we next had the daunting task of deciding who to get to install the system, what size of system to install and which type of panels to select. This was much more complicated than we had imagined as there are so many companies installing solar PV systems and so many options to consider. We decided to spend some time doing research on how the systems worked and who might be reliable suppliers to get a quote from. I would recommend anyone considering installing a system to do similar research before taking the plunge, there are lots of useful resources on the Internet to help you make an informed decision. Take a look at my links section for some of the best sites that I found.

From my own research I found it very difficult to find real figures for how much electricity a system might produce in practice. All installers will supply predicted figures for the amount of electricity that might be generated but there is no way of finding out how realistic these figures are. It would be great to have a network of sites around the country reporting on how their systems were performing so you could see what someone local to you was achieving. As a result I decided to post details of how our system was performing to help others who are considering having a system installed.

I will post details about our system and regular updates about how well it performing soon.