A mini post about our installation’s performance in its first (not such a sunny spring and summer) year.
Our PV installer provided the following predictions: SAP – 1,858kWh and PVSol – 1,962 kWh. In the end we actually generated 2,111kWh so 14% higher than SAP predicted and 8% higher than PVSol. Based this year’s Feed In Tariff figures we can expect to ‘earn’ (made up of FIT payments and savings from reduced imported electricity) around £1,130 in the next year.
Our usage figures for the first year aren’t worth discussing much as it was essentially a building site. Around 450kWh was used for lighting, power tools, cups of tea and a few days when my dad stayed on the site in January with an electric fan heater. The gas was switched off. (This essentially means that the build was Carbon negative in terms of on site primary energy use – purists will have a field day with that tongue cheek claim 🙂 )
Here is a little gadget that is saving some money for some people with PV systems that generate more than they are using during the day. For a while there have been PV add ons that send some PV generated electricity above set generating levels to the immersion heater. This one goes further and actively monitors your generation and your current use and sends the difference to the immersion.The key to the amount you save is dependent on a) the fact that before smart meters you are getting paid as if you are exporting 50% of your generation amount whether you do or not b) the efficiency of your normal hot water system and cost of its fuel. In terms of pure CO2 savings in most circumstances it will be better to export it, in which case your neighbours use it and a powerstation somewhere can turn down their furnace a bit. Transmission losses will also be saved. It’s the altruistic option but for some CO2 is what it is all about. For my situation, where I have a solar thermal system too, its not useful. A system that diverts to a battery store is however an option.
To help us keep our bills down we’re obviously installing low energy lighting throughout. In most rooms this means compact fluorescent lamps and in the kitchen and bathrooms it means 4.5W GU10 LEDs – equivalent of a 40-50W halogen in light output. These were £7 each and we are very happy with their light quality.As LEDs improve and get cheaper for standard bulbs we will convert to them but they aren’t quite there for lights that aren’t on a lot.. [Update 08/13 – virtually all my lights are now LEDs]The picture shows a new LED bulb for a standard bayonet fitting. Its equivalent to a 75W lamp and is a similar light to a standard incandescent lamp when on. We’ve got one of these for our hall as it can be pretty dark and has a lot of traffic. At £35 its a bit of an experimental toy for me though.