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| blog:2024-09-28:estimating_cost_of_electricity [2024/09/28 10:15] – [Here's why that works...] va7fi | blog:2024-09-28:estimating_cost_of_electricity [2024/11/24 12:48] (current) – va7fi |
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| | ~~DISCUSSION~~ |
| | ~~NOTOC~~ |
| ====== Estimating Cost of Electricity ====== | ====== Estimating Cost of Electricity ====== |
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| ===== Here's why that works... ===== | ===== Here's why that works... ===== |
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| In BC, the [[https://app.bchydro.com/accounts-billing/rates-energy-use/electricity-rates/residential-rates/tiered.html |price of electricity]] is 10.97 ¢/kWh for the first tier and 14.08 ¢/kWh for the second tier. So let's take the worst case scenario and imagine that we're always on the //tier 2// price. The math is just a string of multiplication to cancel out units: | In BC, the [[https://app.bchydro.com/accounts-billing/rates-energy-use/electricity-rates/residential-rates/tiered.html |price of electricity]] is 10.97 ¢/kWh for the first tier and 14.08 ¢/kWh for the second tier. So let's take the worst case scenario and imagine that we're always on //tier 2// pricing. The math is just a string of multiplication to cancel out units: |
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| \begin{align*} | \begin{align*} |
| If you look at the units carefully, you'll notice that they almost all cancel out except for \$\frac{\text{\$}}{\text{month}\cdot\text{W}}\$ ((The "hrs" of "24 hrs" cancels with the "h" of "kWh" since kWh means kW \$ \times\$ hr .)) | If you look at the units carefully, you'll notice that they almost all cancel out except for \$\frac{\text{\$}}{\text{month}\cdot\text{W}}\$ ((The "hrs" of "24 hrs" cancels with the "h" of "kWh" since kWh means kW \$ \times\$ hr .)) |
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| So why is this number useful? If you multiply a power consumption in Watts by that number, you'll get a result in \$\frac{\text{\$}}{\text{month}}\$, which is the price per month. For example: | That number means that it costs %%$%%0.102784 per month for each Watt of power that's continuously drawn. So if you multiply that number by the power consumption of the device, the \$\text{W}\$ will cancel out and you'll get a result in \$\frac{\text{\$}}{\text{month}}\$, which is the monthly electricity price for that device. For example: |
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| \$$ | \$$ |
| \$$ | \$$ |
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| The trick to simply divide by 10 instead of multiplying by 0.102784 works because \$\tfrac{1}{0.102784} \approx 9.729... \quad\$ So a better approximation would be to divide by 9.7, but dividing by 10 is so much easier to do in your head, and the result is not that far off, specially since we already over estimated the cost of electricity to full //tier 2// instead of a combination of //tier 1// and //tier 2//. | The trick to simply divide by 10 instead of multiplying by 0.102784 works because \$\tfrac{1}{0.102784} = 9.729... \approx 10\$ . So a better approximation would be to divide by 9.7, but dividing by 10 is so much easier to do in your head, and the result is not that far off, specially since we already over estimated the cost of electricity to full //tier 2// instead of a combination of //tier 1// and //tier 2//. |
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| ===== A Concrete Example ===== | ===== A Concrete Example ===== |
| Equipment on dedicated 12 V system that's on 24/7: | Equipment on dedicated 12 V system that's on 24/7: |
| * Internet modem, switches, and Wifi Boosts | * Internet modem, switches, and Wifi Boosts |
| * [[https://scarcs.ca/howto/echolink#sysop |Echolink radio and computer]] | * [[https://scarcs.ca/links/echolink#sysop |Echolink radio and computer]] |
| * [[https://wcaredn.ca/setups/va7fi/home |AREDN hAP, two AREDN dishes, one AREDN VOIP Phone]] | * [[https://wcaredn.ca/setups/va7fi/home |AREDN hAP, two AREDN dishes, one AREDN VOIP Phone]] |
| )) | )) |
| on a dedicated 12V system. The system is fed with a high quality / high power 12 V charger with backup batteries and solar panels. In the winter, the solar panels don't get any sun and the charger puts out a constant 75 W (and goes up when I'm transmitting). In the summer, the solar panels provide about half the electricity needed. | on a dedicated 12V system. The system is fed with a high quality, high power 12 V charger with backup batteries and solar panels. In the winter, the solar panels don't get any sun and the charger puts out a constant 75 W (which goes up when I'm transmitting). In the summer, the solar panels provide all the electricity needed for up to 16 hours. |
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| That means that my internet and radio system costs me about $7.50 / month of electricity in the winter, and half that in the summer. | That means that my internet and radio system costs me about $7.50 / month of electricity in the winter, a third of that in the summer. |
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