Sunday, 30 September 2012

Solar PV a year on and some illuminating thoughts

At the beginning of September, our 2100 kWp Solar PV array had been installed for an entire year.  The output was 15% over what had been predicted by the installer, generating  just under 2000 kWh in the year, and the investment is still looking to pay off in just over 7 years.

I also noticed that for the price I paid, you can now get a system that’s twice as big, so even though the FIT rate has halved, you can still get your investment back in 7 years, while generating twice as much as I am.

However, in the Northern Hemisphere, the days are getting shorter (watch it change on your PC’s desktop with Terminator for Windows Desktop) and it’s got me thinking about how we can shave bit more off of our consumption.

Ikea have an offer on in the UK for the next few days, giving you £3 off each LED bulb you buy.  This website also looks promising:

Should I replace all my CFL bulbs?

For example, this 60W replacement (at £11.95) replacing an 11W CFL bulb to a 5W bulb will pay for itself after 100 kWh at 11p/kWh, or about 20000 hours.  Assuming the light is on for an average of 3 hours a day, that will take 18 years to pay for itself—maybe not worth it just yet, as you can currently get CFL bulbs for about 10p each in the UK (heavily subsidised).

What about CFL downlighters?

We do however also have 8 CFL downlights that are probably reaching the end of their life (they’re on many hours a day in the kitchen), and the best price I can find at the moment for them is Pack of 3 - Megaman BR0711i Ingenium GU10 Spot Bulb 11W Warm Whitefor £14.99.  Where these apparently direct replacement GU10 LED 4.5 W  lamps are £9.95.  If the lights are on 4 hours a day, I save 10p every five days, saving £7.30 per year.  Replacing all 8 bulbs (£40 difference in price) will take just over 5 years to repay the investment, so this probably is worth doing.

How about Fluorescent Tubes?

We also have some fluorescent tubes in our bathroom placed beside a large mirror.  Three of these at 30W uses quite a lot of electricity, and I actually don’t like them very much anyway.  Also, the seem to light up a lot of the box they’re in and not so much of the mirror.  But, these IP68 LED Tape Lamps look like they might be exactly what I need.  5 meters of tape should be enough for the job at 24W and output 1800 Lumens, and again will cost just under £40, and I’ll also need a driver for the LEDs that costs about £20.  Every 15 hours these are on, I’ll save 1Kw of electricity, so they’re paid for in 9000 hours, which at an hour a day for a bathroom will take around 24 years to pay back.

That’s not a great return, but I might do it anyway.  I can probably build it in such a way that if they don’t work there, I can repurpose the strip of lights for use somewhere else.