Getting the best from PV solar panels

So you are the proud owner of an expensive Photo Voltaic solar panel array on your roof and are looking forward to the financial benefits that will be provided with your wise investment. How exactly do you achieve this and what happens if you don’t bother?

Electricity prices are projected to increase by 100% in the next ten years, this will mean that instead of paying 12-15 pence per kWh (plus VAT at currently 5%) you may pay in the region of 25 to 30 pence per kWh + VAT instead.

If you maintain your present day electrical consumption, will your income increase by the same margins to cover this additional cost? We know that the feed-in tariff will be paid for a period of 25 years from commissioning of the panels but what about the power that you sell back to the National Grid?

Let’s say that your annual electrical consumption is approximately 4500 kWh or “units” as displayed on your electrical meter. This is probably a fairly average figure for a home in the Blackdown Hills with oil central heating and no mains gas connection.

An average PV installation could provide approximately 2000 kWh per annum, this would in theory mean that your electrical consumption could be reduced by (4500 – 2000) kWh = 2500 kWh. Out of this you will be paid for only half of the 2000 figure (1000 kWh @ £0.03 per unit = £30.00) so what happens to the other 1000 units? Of course it is used by the National Grid and you will not see any financial benefit from it. 

As of today there are not yet any commercially available storage systems such as batteries, so how do you harness more of what you are producing? In practice your domestic electrical consumption from the grid is more during the Winter and less in Summer. Correspondingly the PV panels produce their best performance from April to September not withstanding the appalling 2012 weather!

If the majority of power is produced in the Spring to Autumn period, how can we best capture it? Our PV installation has an Ethernet and Bluetooth connection from the loft mounted “Sunnyboy” inverter to our PC. Using the software from Sunnyboy, it is possible to check the PV panel output from our desktop PC at any time. 

Of course there are the simple things to do when your PV installation is producing its peak power.

  • Use the washing machine
  • Use the dishwasher
  • Use any other electrical appliance that uses a lot of power.
  • Use an electrical immersion heater instead of oil fired water heating

There are a number of ways in which to divert your PV power to an immersion heater. These range from a range of electronic devices priced up to £1700 down to a humble £20 mechanical pin timer designed for immersion heater use.

Another application could be heated towel rails. There are specific models designed for installation to bathrooms but we have fitted towelling radiators connected to the oil-fired central heating combined with self-contained electrical heating elements. In this way when we switch off the oil heating, the power produced from our PV panels can used to warm up our bathrooms and to air towels. Again these are controlled by simple timer switches. You will also save heating oil too if not heating up hot water using the central heating system. 

Obviously as mentioned earlier, it is not possible at the moment to successfully store electrical energy produced by your PV panels but by carefully knowing when your panels produce their best power output, it is possible to operate equipment and appliances to successfully use the power that you make rather than to let it be sent back to the grid with no benefit for your household.

Needless to say, any electrical work should be installed by a competent person working to most recent electrical regulations and periodically tested for safety requirements. 

To sum up, you should be aware of the benefits of your PV panels and strive to use as much of that power produced to offset and reduce your ultimate electricity bill.

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