Calculating running costs - checking my figures

[garrymum]

I am thinking of replacing my 150W PIR activated light with a 42w low voltage floodlight which has built in photocell and would be on during darkness. I have based my calculations on the following:-

Wattage of floodlight = 42w
Average monthly usage = 300 hours
Electricity cost = 14.70p per kwh

I get this to cost around £1.85 per month, which seems low to me. Could anyone please check my figures?

Thanks

 

[Spark123]

Based on the information you provided your sums appear correct, what sort of floodlight?

 

[garrymum]

Based on the information you provided your sums appear correct, what sort of floodlight?

Thanks for the reply, something on the lines of http://www.screwfix.com/prods/35156...omic-Low-Energy-Floodlight-with-Photocell-42W

 

[Spark123]

I'm not 100% sure with CFL lights, some discharge lights take a little bit more than is stated on their lamps. Might be worth sticking one on an ammeter and seeing current it really draws.