DIYbanter - Water Bills

N. Thornton wrote:

Fwom:The Natural Philosopher )

Additional gas bill per 2000 hours to replace lost heat? probably

about £5

So £9.23 per 2000 hours in reality.

Good point.

2000 hours of 100-23w = 2000x77w = 154kWh
gas @1.5p/kWh = £2.31

Heating in use lets say 2/3 the year, so the saved money in that is
2/3 x 2.31 = £1.54

Thus real saving figure now:

£13:23 to £9:03 per light fitting per 2000 hours.

Last questions are how many such fittings does it take to light a
house, and how long does it take to use the lights for 2000 hours.

How many fittings to light a house? Those halogen spots are pretty small
area wise in terms of what they do.

I would say that 25W/sq meter is reasonable. I.e. abourt 2 sq meters per
50W spot. Although we are running at far less than that here mainly.

3000 hours is one third of a year. 10,000 hours per year is an 'always
on' figure.

If the lights go on say at 6pm and off at 12pm in any given location,
that's a 25% duty cycle - so 2500 hours per year.

As an intereting aside, I have 6x5 meter rooms one of which is teh
kitcen,. The Aga fully heats that except on the coldest of nights, at a
rated 600W output.

To light it at 25W/square would take 750W. More than enough to heat it
completely. In practice is has a mere 520W and dark areas. It's got
9x50W LV halogens and 3x60W candle bulbs.

In an ideal eco world it would probably have 6x25W sstrip lights :-)

But those would really look ugly...

I look forward to hoghly decorated OLED lighting in due course.

NT