Quick Maths for watts and cost and effort

Pho3nix

The Legend
Joined
Jul 31, 2009
Messages
27,403
#1
Hi,

Have about 40 gu10 10w lights. Considering changing these to the 3.5w variety but trying to get my maths right.

New ones = 40 * 3.5w = 140w
Old ones = 40 * 10w = 400w

If charged at the tariff of R1.1858 per kwh then would the cost difference be R46 odd?

(5 Hours a day of 3w = (140w*5) = 0.7kwh * 1.1858) = R0.83006 = R24.9018
(5 Hours a day of 10w = (400w*5) = 2kwh * 1.1858) = R2.3716 * 30 days = R71.148

40 lights is a cost of R800 odd so ROI in a year an a half. Worth the effort?
 

alqassam

Expert Member
Joined
Aug 11, 2014
Messages
2,240
#2
Hi,

Have about 40 gu10 10w lights. Considering changing these to the 3.5w variety but trying to get my maths right.

New ones = 40 * 3.5w = 140w
Old ones = 40 * 10w = 400w

If charged at the tariff of R1.1858 per kwh then would the cost difference be R46 odd?

(5 Hours a day of 3w = (140w*5) = 0.7kwh * 1.1858) = R0.83006 = R24.9018
(5 Hours a day of 10w = (400w*5) = 2kwh * 1.1858) = R2.3716 * 30 days = R71.148

40 lights is a cost of R800 odd so ROI in a year an a half. Worth the effort?
Should be because they will last way longer than 1.5yrs.

Also 1.18 kWh is cheap where do you live in a power station?
 

Pho3nix

The Legend
Joined
Jul 31, 2009
Messages
27,403
#5
Should be because they will last way longer than 1.5yrs.

Also 1.18 kWh is cheap where do you live in a power station?
Apparently what we are paying within the estate if I am to believe the invoices I’m looking at
 

alqassam

Expert Member
Joined
Aug 11, 2014
Messages
2,240
#6
Makro has osram 3w for 6 for 100 on special spend 700 and get 42.

Just wait for the special and buy then

You Payback faster
 

alqassam

Expert Member
Joined
Aug 11, 2014
Messages
2,240
#8
Also if you start going low power on everything it makes it easier to move onto solar when you have extra funds.

Now you only need 1 X 320w panel to run your lights
 
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