Would someone check my calculation please...
I have been considering fitting downlighters in my kitchen.
The kitchen is roughly 7m by 4m. Reading other posts on this BB it looks as
though I should go for around 15 downlighters + additional under cupboard
lights for effect...
My calculation is:
50W per light
Lights on 15 hours per day
15 * 50/1000 * 0.07 * 15 * 365 = approx £300 per year running cost. Any
additional under-cupboard lights are extra on top of this, as are
replacement bulbs, etc.
I assume that low voltage downlighters cost the same to run as mains
Seems a bit steep to light just one room in the house!
[At the moment I have a 60w strip light and a 20W low voltage pendant which
gives adequate (but not sexy) lighting and only a tenth of the running
Should I be considering something other than downligters? Is this the cost
of a modern-looking kitchen?
15 hours a day seems pretty steep....................in winter you
would have to have the lights on for all the darkness hours (even
when you are asleep!)...............and during the summer you would
be using the lights in daylight!!!! I think you need to recalculate.
I doubt my kitchen lights are on for more than 2-3 hours a day in
winter and much less in summer.
My kitchen is 3.3m x 3m and we have 6 50W LV halogens lighting the main
area, plus 2 more in a glazed cupboard. The amount of light they produce
is more than adequate for my purposes.
Presumably you don't have a window in this room and you plan to leave
the lights on all day?
Even if you really do need to have artificial lighting in your kitchen
for 15 hours/day, do you need to have all 15 lamps burning all the time,
or could you divide it into general illumination/tasks?
Then teach them, like my father taught me!
15w compact fluorescents in the corners above the cabinets work well, as
they wash the ceiling with light which is diffused around the room. These
could stay on for extended periods.
The halogens provide excellent bright light, but 750w won't be needed all
the time, as you seem to concur.
You could go for 3 independently switched lighting sources:
10w - 20w of under cabinet fluorescent strips,
Hidden CF wall/ceiling washes to provide general illumination,
LV halogens for detail lighting and making the missus go ooohH.
I'll take this opportunity to rant, if you don't mind. This isn't
personal - lots of people do what you are proposing :-)
I really, *really* don't understand this recent obsession with LV
halogens; specifically with using dozens of them to light a room.
When I was growing up, each room had a 60W/100W bulb, and maybe a
reading lamp/desk lamp as well. That was plenty.
Why anyone would need or want 750W to light their kitchen is beyond me.
I totally do not understand it.
Our kitchen makes use of 3x 21W CFs, and we find this more than enough.
Regardless of cost, to use 750W to light one room is *obscene*.
It's more about misusing task lights for general lighting.
Using appropriate incandescent luminares for providing general
lighting would knock the figure down considerably. Downlighters
are not for general lighting, so unsurprisingly they are very
inefficient if you try to misuse them that way.
They're also very good for puncturing holes in your previously
fire resistant ceiling, and as an added bonus, each has the power
and heat available to behave as an incendiary device given the
opportunity, and their excellent positioning in a brech of the
The calculations are OK, but the assumptions are probably
First of all, I doubt that you would need all 15 lights for 15 hours a
day, the year round. You can divide the lights into groups and
switch some on at a time. For example, I have some in the ceiling
away from the walls and some closer to the walls to give reflected
light. I probably have about a third of them on for many purposes
and more when needed.
Don't you like sex? ;-)
I also used small high frequency fluorescent fittings underneath the
cupboards for certain jobs.
Being able to mix and select different types of light at different
times is quite appealing.
| > Don't you like sex? ;-)
| It doesn't usually cost this much ;-)
Perhaps you should drop subtle hints to the missus that lots of overhead
halogen lighting emphasises bags under the eyes, wrinkles, moustaches (hers)
and encourages premature aging.
Of course if she wants her kitchen lit up like a pathologist's dissection
I don't think you need to do that. You can split lighting into
general, accent and task.
Most of the time we end up with three different combinations and I
have the switches to achieve that with different sets hooked to each.
It does, you know. You just don't realise it...... :-)
Using switching as described above, I have 3 switches, each of which
turns on a different scenario. One is for cooking, another for other
work in the kitchen and the third is when nothing much is happening
and I need light to walk through or raid the fridge so just some
accent lights near the wall. It's then just a case of throwing an
additional switch when needed.
You can mix technologies of course, although I prefer to keep
fluorescents of all types to a minimum because I find them bilious in
My kitchen has 2 semiflush light fittings. (15W yellow compact fluorescent
bulbs). This give a nice soft warm glow to the room. For task lighting, I
have 4x18W tubes under pelmets and 1x30W tube up the chimney for the range.
This gives a total of 132W when it is all on. It is a LOT of light. The
under pelmet lights only need to be on when cooking.
Why have 750W just for the main lighting? Do you have a one man vendetta
against Bangladesh? Perhaps you like the sight of drowning Polynesians?
750W seems to be amount recommended by those with downlighters for a kitchen
of 28 sq m. Perhaps downlighters are less efficient/practical?
It is a shame that strip lights don't look nicer... They seem much more
practical in a kitchen...
I found this quote rather amusing, "I think the wife/children would object
to switching lights on/off all day long."
I like a place to be well lit but there is a limit surely!
Do they cope with flushing the toilet or have you arranged for that to
I suppose a PIR type of switch would be possible - we have them in the
offices where I work. They dim the lights out after about 20 mins of no
Well lets add in bulb costs. 15 lights 15 hrs a day = 225 bulb hours
/day = 0.1125 bulb life per day if using 2000 hr bulbs. So you will be
replacing bulbs at the rate of 1 per 9 days - on average.
At say £2 a bulb (you can ignore delivery since youll be buying in
365 x 0.1125 = 41 bulbs per annum, or £82 pa, and some exercise :)
So its nearer £400 a year. For 1 room.
no. mains halogen cost more, mains cfl cost less, traditional mains
filament cost more.
How many rooms have you got...
Fls are very efficient, and routinely badly installed and poorly used.
They can be made to look fine, but few people seem to have any idea
how to do that. I've been in places lit almost entirely by fls, and
they looked good. Unfortunately widespread bad practice gives them a
a) avoiding downlighters which are energy inefficient for 2 reasons
- theyre halogen not cfl
- they light up the floor which wastes a lot of light
b) using cfl not halogen
c) not leaving lights on all day long
d) using a more sensible level of lighting than 750w
e) having the lights on a bank of switches so you can put on what
youre comfortable with at the time
f) using small lights where theyre needed
g) training your family to be responsible
and if you want to take things to extremes, use an external reflector
to get more sun and skylight in through the window. It works well.
no, its the cost of what you propose to do. There are plenty of other
ways to have a modern looking kitchen. There are even ways to have
downlighters without the cost you are looking at here.
no it increases it. I can explain if needed.
I think they just dont know what theyre doing. Anyone who imagines
having a 500w halogen floodlight in the room, and then adding some
more, will realise its not a bright idea.
I also wouldnt go for PIR, they simply dont make good choices, and are
anoying and wasteful.
Want some new ideas?
I would like flourecsent tubes if I could find some way of making them look
nice. I think think that they make a better working light. Has anyone seen
any fittings, or got any tips for installation, that would look acceptable?
I've done the lighting in two kitchens in last few years.
In both cases, I used T4 fluorescent fittings (CPC, B&Q) under the
cupboards behind tiny pelmets, and concealed fluorescent tubes on
top of the cupboards bouncing light off a white ceiling.
This has worked very well with excellent all round lighting,
excellent task lighting on the worktops and absolutely no glare.
The under cupboard and on cupboard lights are separately switched.
You should consider the colour temperature (and make sure all the
tubes are the same). For domestic kitchen lighting levels you want 2700K.
This will also match the colour temperature of the other lights in your
house and make the kitchen feel warm. If you want to install a
significantly higher level of lighting in the kitchen than is perhaps
the norm for domestic use, then you can also increase the colour
temperture to 3500K, but this will look cold and lifeless unless the
lighting level is much higher than you would normally find in a
domestic residence. This high level of lighting is something you might
particularly want to consider if the kitchen has no natural light and
you will be using the lights all through the day. However, it can be
overpowering in the early morning and evening when we don't expect
such high light levels or high colour temperatures.
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