My First Measured Fill-up

excellent! did you enter into the spreadsheet?

 

Go Bears!!! Welcome to Plug-in Prius, from the Berkeley Class of '89!

 

Alameda to Santa Clara -- Hwy 880 to 237 to Lawrence.

 

Not sure of your logic. Are you suggesting we calculate MPG based on adjusting the energy content of a kWH based on the cost?

 

Bear,

Add your Fillup data to the first tab named "Enter Data Here" and I'll move it to the "MPG" tab and back it up.
Welcome to Google Docs

 

Cost is important...but not a good measure to be able to compare efficiency...gas prices and electricity prices vary day to day and by geography. To be useful, IMO, we need to compare based on units that don't change, then people can convert this to their own costs.

MPGe is miles per gallon equivalent, where the energy content of gasoline (114,000 BTUs per gallon) is equated to ~33.7 kw-hrs (where 1 kw-hr = 3412 BTUs).

Technically we should be using a ~3% lower value for BTUs per gallon of gas because it generally has 10% ethanol.

Mike

 

Why not use cost per mile
Total cost of gas + total cost of electric/miles driven

1243 miles driven
Fuel consumed
10 gallons gas at $3.92/ gallon cost $39.2
263 kWh at $0.0335/kWh total cost $8.81
Total cost $48.01

$48.01/1243 miles= $0.039/mile

Assume std prius 50 mpg

Gas 1243/50= 24.86 gallons cost $97.45

$97.45/1243=$0.128/mile

 

It's not as simple as $0.04 a kwh at off-peak rates. You also have to consider what your peak rate was before vs now. If you were paying $0.09 on E1 before at peak time and paying $0.12 on E9-A now, then it's not really costing you $0.04 a kwh to charge your car. Those off peak kwh are being subsidized by your peak rate use.

That's the reason I haven't switched to E9 yet. I'm charging $0.15 average per kwh for my car according to PG&E. (It's really $0.29 per kwh because the entirety of the car pushes me into tier 3.) If I switched to E9, I could be charging for $0.09 average per kwh. No brainer, right? But because of what I just wrote, my math shows that switching my rate will decrease my total monthly bill by $5 or so. That's hardly worth becoming Electricity Monitor and scolding 3 adults when they want to boil an egg at 2 PM during peak time or wash their clothes on a weekday.

 

If you have Solar, you should probably stick to E-6. It's better for maximizing solar credit production than E9-A. You lose 1 hour of peak rate production in summer on E9-A, right around the time your solar array is in max production. Partial-peak rates are higher on E-6 as well in summer. For winter off-peak you'll be earning slightly higher credits, too.

 

2 things to keep in mind:

1) You can only switch rates once a year, so you'll have to live with this for a while.

2) The standard Solar net energy meter they give you isn't a smart meter with hourly updates. They have to come by to read the meter every month. In 2012 they were supposed to start swapping them out for smart-meter enabled Solar meters, but I haven't heard anything further. Our system was turned on in July 2012, at which point you think they would've have just installed a smart-meter Solar meter to begin with, but alas, that wasn't the case.

What size system do you have and how long have you had it?