> 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.
************************************************************************
OK, lets take that lot and see what we get for an 800 sqft house.
For an 800 sqft house, thats 72 sqm. Youre using 520w per 30m2, =
17w/m2, so at that level the whole house would require 1.25kW of halogen lighting at 25% duty cycle.Yearly run cost for halogen:
2500/2000 x 1250/100 x £14.80 to £19 = £231 to £296 per year, for both bulbs and leccyYearly run cost for CFL: 2500/2000 x 1250/100 x 4.23 = £66 pa, including both bulbs and leccy.
Saving by going over to CFLs is less than the difference due to heating effect:
2500/2000 x 1250/100 x 13.23 to 9.03 = £206 to £141 per year = £9800 to £14000 per 70 years.Also the CFLs will make life a lot cooler in summer. How many degrees does your 600w raise your kitchen? CFLs would quarter that heat gain. Modern well insulated houses will make that heat gain even worse.
NT