July 2012 is Best Month So Far for Solar Panel Production

July 2012 has been our best month so far for electricity generated by our solar panels and we still have 1 day to go. As with June it really makes you wonder how incredible the electricity generated by solar panels would be if we had an amazingly sunny summer in the UK.

If we can beat the PV-GIS and SAP2009 figures with the summer we have had this year then a good summer could well be off the scale.


July 2012 is Best Month So Far for Solar Panel Production

So far July is giving a total generation of 384kWh compared to 351kWh prediction. The forecast for tomorrow isn't great so I'm not expecting the break the 400kWh barrier.

Effect of Shade on Solar Panels Output

What is the Effect of Shade on Solar Panels Output?

When installing solar panels it is important to choose a location that has minimum shading as electricity generated by solar panels drops when any one panel or part of a panel is shaded. Until today I'd not realised quite how much difference it makes.

Our solar panels are on our main roof which also has a velux window fitted. This is very convenient for checking the condition of the panels and for stopping pigeons nesting under them. It also has the potential for creating shade on the panels when the window is open!


What is the Effect of Shade on Solar Panels Output?

When checking the solar panel output logs in Sunny Explorer I noticed that there was a sharp drop in output from the panels despite it being a totally sunny day. On further investigation I realised that the velux window had been opened due to the heat and that as the sun dropped in the sky it was creating a shadow across the 2 panels.

Despite the shading only covering a tiny fraction of 2 panels over the course of about 90 mins at the end of the day we lost around 1kWh of solar electricity generation. Imagine how much could be lost by more significant shading over a longer period of time.

How do SAP Figures Compare to Actual Solar Panel Output?

When we were getting quotes for our solar panels all installers had to provide standard figures to show the estimated output of the panels. Some installers also provided much higher numbers to justify their installations as being superior.

How do SAP Figures Compare to Actual Solar Panel Output?

Now that we have had the solar panels for 8 months it is interesting to compare the actual output with the SAP 2009 figures that were provided at the time of installation.

How do SAP Figures Compare to Actual Solar Panel Output in winter?

Our solar panels are 14 Sungrid panels at 215W each giving a total potential output of 3010W (3.01kWp) The SAP 2009 annual yield was quoted at 2479kWh.

So far as of 13 July 2012 we have already generated 1972kWh of electricity in one of the worst British summers since records began with the wettest April and June since 1910. Extrapolating the generation figures over the next few months we could well see a total for the year of 3000kWh.

Solar panel generation - actual month by month output figures for the UK


Solar panel electricity output in the rain

Using PV GIS data to calculate the annual estimated output gives a figure of 2905kWh for the electricity produced by our solar panels for the year which again we should be able to beat even with the current amount of rain!

Comparison of predicted solar panel outputs for different estimation methods

SAP 2009                                 2479kWh
PV-GIS                                    2905kWh
Current Estimate on actual:     3000kWh

How Does Rain Affect Solar Panel Electricity Generation?

How Does Rain Affect Solar Panel Electricity Generation?

In what has become a depressingly familiar sight this year today has been another wet day. This summer has been quoted as the wettest since records began with April and June having more rain that any month since 1910. Fortunately not as wet as some parts of the country with a month's worth of rain falling in a few hours but sunshine and showers meaning yet again our solar panels have not been generating at their maximum that we would expect for the summer.

How Does Rain Affect Solar Panel Electricity Generation?

On a completely rainy summer day the electricity generated by solar panels can be less than 10% of the amount generated on a perfectly sunny day so for our panels we have sometimes got 2kWh for the day whereas a sunny day can be over 20kWh.

On a day like today though with mixed sunshine and showers the amount generated is not so bad and can equate to around 50% of the electricity you would generate on a sunny day, with around 10kWh generated today.

Peak electricity generation during mixed sun and rain

In fact on a rainy day with mixed sun and rain the peak generation can actually be far higher than the peak on a sunny day as the panels get cooled down by the rain so the immediately hit their maximum when the sun does come out. On a sunny day the peak output can be around 2.5kW but on a mixed day just after a rainy spell the peak can jump to as high as 3kW when the panels are cool.

This link explains how temperature affects the electricity output of solar panels

Problem with Imperial Gas Meter Shown as Metric on Bill So Undercharged

Since we moved into our house in 1999 we have had the same Imperial Gas Meter that reads in Cubic Feet.

Imperial Gas Meter Billed as Metric and Undercharged

We have been with the same supplier and always thought our bills were very reasonable but assumed it was because we were very careful to not overheat the house and time usage to match when we are home.

We always submitted readings to Scottish Power as requested and shortly afterwards received our bill. Nowhere on the bill or the gas meter readings section was any mention of the units that the consumption was measured in.

In 2010 we received a letter from Scottish Power that our meter had been recorded on their systems incorrectly as a metric meter when it was actually an imperial meter so we had been undercharged for our gas for 11 years. Scottish Power agreed to not backdate the charges but they amended their system so that the meter was now recorded correctly as an imperial meter.

How many people have been billed for Metric gas consumption and consequently undercharged? Equally if you are billed for imperial consumption with a metric meter you will be overpaying the gas company for your usage.

The factor involved appears to be 2.8x so if you are billed for imperial consumption with a metric meter you will be overpaying 2.8x more than you should

If you are billed for metric consumption with an imperial  meter you will be paying nearly 30% of the actual cost of the gas supplied.

Maybe the first thing the gas companies should be doing is showing the units on the bill and for any readings you supply - at least then you have a chance to check they match your meter.

June Solar Panel Generation Stats Now Loaded

The data from the Sunny Explorer application has now been loaded to the website

http://solar-panels-review.321web.co.uk/monthly-pv-solar-panel-generation.php

Despite being the wettest June since records began in 1910 the electricity generated was still on target which shows how huge the electricity generation would be if we had a massively sunny month. On the whole June was another poor month for solar power as it was very mixed weather as April and May had been.