The real cost of GU10s

Before we had the kitchen upgraded, the dining room had the brightest lights (eight, 40 watt standard bulbs) and it was thee room to be in during the winter because of the light. That all changed when we had a new kitchen fitted back in 2001. Back then the modern(ish) thing to have in your redecorated room were GU10 halogen spotlights and we had 9 added in the kitchen and 4 in the bathroom. Each GU10 spotlight uses 50 watts and when all on, the room is really well lit. While 50 watts might not seem a lot, when you work out how much that equates to over an average year, it soon adds up!

I’ve made a simple spreadsheet which roughly represents the cost to our family from having these spotlights on.

Click to download the spreadsheet. MD5 checksum: 8f90bce78a6fc865f1b7564b170121eb

If you’re interested in seeing what your own lighting costs you, simply fill in c7 through c18 with your estimated daily average time the lights are on each month, the number of bulbs, watts per bulb and the cost per unit of electricity (near total). The spreadsheet should add up the other values and present a total estimated yearly cost of using your lights.

Recently the cost of LEDs has dropped quite a bit and the technology has moved on too. We first bought an LED replacement GU10 over a year ago and were not impressed. The light produced was in a very narrow beam and bright blue! It made the entire room seem very cold. The second wasn’t much better. However the third one, which we bought in October 2011, is very impressive! It’s a 4 watt GU10 LED replacement with a warm white light. Having tested it out, the light is very similar to the old bulbs in the ceiling and the colour is no longer bright blue, but a slightly off white heading to yellow colour.

We’ll be upgrading the entire ceiling to use the new bulbs as soon as the price drops. Currently each bulb is £8.28 (including VAT), which would take a year and a half to make back, but as soon as the price drops to £5, I’ll be upgrading J

Interested in buying LED lights? See here: 4 watt GU10 LED warm white

Number of bulbs

9

Watts per bulb

50

Total kWh

0.45

Estimated number of hours a day lights on Total days in month Estimated hours per month Estimated kWh per month
January

3

31

93

41.85

February

3

28

84

37.8

March

2.5

31

77.5

34.875

April

2

30

60

27

May

1.5

31

46.5

20.925

June

1

30

30

13.5

July

1

31

31

13.95

August

1.5

31

46.5

20.925

September

2

30

60

27

October

2.5

31

77.5

34.875

November

3

30

90

40.5

December

3

31

93

41.85

Total

365

789

355.05

Price per unit (pence)

17.5

Total estimated cost per year (pounds)

£62.13

Solar Panel Output

When I was deciding which solar company to go with, I found out that some of the inverters had inbuilt internet access and others could have data logging added. The system I have (Sunny Boy 3800 and bluetooth piggyback with Sunny Beam) allows me to collect csv files of the day before output. The csv contains limited data, max panel power in a ten minute bracket, total energy generated and all time energy generated, but this is where PVOutput comes into the equation. PVOutput allows one to manually (or automatically if you have the correct setup) upload that data to the website, where it’s stored for free, provides statistics on the data and allows comparisons against other systems.

Here is our output graph:

I’m currently working on an app which when the Sunny Beam is plugged in, will read the new files and send outputs to the website automatically, which will save time and prevent typing errors.


Solar Panels!

I had my solar panels switched on today! I’ve wanted solar panels or a wind turbine for over 3 years now and finally have my own.

The process started in July this year when I decided to find out the true cost of installation. I contacted a local building firm who came the next month to give a quote. After that a neighbour recommended getting some more quotes and three more later I’d chosen the company I wanted to use.

I chose to go with Ecohouse (although two other quotes were real contenders*) as my neighbour used them and he highly recommended their installation team. I signed up and sent my deposit mid September and installation has taken place this week. There have been a number of small issues during the installation (E.g. asbestos), so instead of taking a day the installation was spaced over 5 days, but the quality of installation is fantastic, the installers very friendly and I’d highly recommend them myself.

Details about the system:
250W Suntech solar panels – Total 4kwh peak
SMA Sunnyboy 3800 inverter with Sunny beam wireless monitor

* Eco-energyUK and BSG Property Services