Difference between revisions of "Appliance energy saving"
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+ | How to assess the energy saving of a new product, to decide whether its worth replacing to cut costs. | ||
− | First you | + | |
+ | ==TV example== | ||
+ | In considering replacing a CRT [[TV]]... | ||
+ | |||
+ | First you need to know the power consumption of the 2 sets you want to compare. The label on the set indicates the max consumption, and figures can be calculated from those. If you want more precision, you'd hook the 2 upto an energy consumption meter (killawatt etc) and measure their consumption exactly. | ||
Example: | Example: | ||
− | Say a TV eats 100w and you watch it for 2 hr per day. (I'm picking easy figures) | + | Say a CRT TV eats 100w and you watch it for 2 hr per day. (I'm picking easy figures) |
# Consumption = 0.1kW x 2hrs = 0.2kWh per day = 73kWh / yr | # Consumption = 0.1kW x 2hrs = 0.2kWh per day = 73kWh / yr | ||
# Price of electricity = 12p/kWh | # Price of electricity = 12p/kWh | ||
# So annual energy cost = 73 x 12p = £8.76 / yr | # So annual energy cost = 73 x 12p = £8.76 / yr | ||
− | # If typical life expectancy of appliance = 8 yrs, thats £70 per life of the product. | + | # If typical life expectancy of [[Appliances|appliance]] = 8 yrs, thats £70 of [[electrical|electricity]] per life of the product. |
Now compare an LCD with 70w consumption | Now compare an LCD with 70w consumption | ||
− | # cost | + | # elec cost = £6.13/yr = £49/ 8yrs |
# Difference = 70-49 = £21 | # Difference = 70-49 = £21 | ||
− | + | The purchase price is greater than the electricity saving, so the LCD never pays its savings back. | |
+ | |||
+ | |||
+ | ==Fridge freezer example== | ||
+ | A faulty 70w [[fridge]] freezer runs continuously. Is it worth replacing? | ||
+ | |||
+ | 0.07kW x 24hrs x 365 days = 613kWh/yr | ||
+ | x 13.5p = £83 per annum run cost | ||
+ | x 10 yrs = £830 run cost | ||
+ | |||
+ | New machine rated to eat 0.75kWh/day = 274kWhpa | ||
+ | x 13.5p per kWh = £35.59 /yr | ||
+ | x 10 yrs = £356 run cost | ||
+ | + £320 purchase cost = £676 total cost | ||
+ | |||
+ | Thus a brand new machine works out £154 cheaper over 10 years than keeping the old one. | ||
+ | |||
+ | |||
+ | ==Real consumption== | ||
+ | Ratings plates give maximum consumption, and this isn't always the same as real world consumption. Most LCD TVs & monitors consume the same power regardless of program content, CRT power consumption varies according to picture brightness, thus is below max rating a lot of the time. So in practice the figures are more in favour of the CRT set than the ratings plates suggest. | ||
==See Also== | ==See Also== | ||
+ | * [[Appliance power consumption]] | ||
* [[Special:Allpages|Wiki Contents]] | * [[Special:Allpages|Wiki Contents]] | ||
* [[Special:Categories|Wiki Subject Categories]] | * [[Special:Categories|Wiki Subject Categories]] |
Latest revision as of 23:43, 7 August 2017
How to assess the energy saving of a new product, to decide whether its worth replacing to cut costs.
TV example
In considering replacing a CRT TV...
First you need to know the power consumption of the 2 sets you want to compare. The label on the set indicates the max consumption, and figures can be calculated from those. If you want more precision, you'd hook the 2 upto an energy consumption meter (killawatt etc) and measure their consumption exactly.
Example:
Say a CRT TV eats 100w and you watch it for 2 hr per day. (I'm picking easy figures)
- Consumption = 0.1kW x 2hrs = 0.2kWh per day = 73kWh / yr
- Price of electricity = 12p/kWh
- So annual energy cost = 73 x 12p = £8.76 / yr
- If typical life expectancy of appliance = 8 yrs, thats £70 of electricity per life of the product.
Now compare an LCD with 70w consumption
- elec cost = £6.13/yr = £49/ 8yrs
- Difference = 70-49 = £21
The purchase price is greater than the electricity saving, so the LCD never pays its savings back.
Fridge freezer example
A faulty 70w fridge freezer runs continuously. Is it worth replacing?
0.07kW x 24hrs x 365 days = 613kWh/yr x 13.5p = £83 per annum run cost x 10 yrs = £830 run cost New machine rated to eat 0.75kWh/day = 274kWhpa x 13.5p per kWh = £35.59 /yr x 10 yrs = £356 run cost + £320 purchase cost = £676 total cost
Thus a brand new machine works out £154 cheaper over 10 years than keeping the old one.
Real consumption
Ratings plates give maximum consumption, and this isn't always the same as real world consumption. Most LCD TVs & monitors consume the same power regardless of program content, CRT power consumption varies according to picture brightness, thus is below max rating a lot of the time. So in practice the figures are more in favour of the CRT set than the ratings plates suggest.