When is it actually cheaper to run on gas alone?

[zimm25]

I'm sure some of the smart owners out there have figured this out, but at what price point does it make it more cost effective to run on gas alone?  Obviously the variable is electric price, but there must be a fairly simple calculation that can be made.  As Connecticut electric rates climbed 30% over the past 3 years ($0.20/kwh) and gas prices have fallen, the cost savings has to be very minimal at this point.  

 

Additional considerations must be:

 

1)  Charging efficiency - particularly on hot days when the battery pack has to be cooled.   

2)  Battery efficiency - a) as the battery gets older AND b) as winter temperatures decrease efficiency.

 

I love driving in electric mode and think it's better to use the battery rather than petroleum products, but I'm curious about the true costs balance.

 

Anyone figured this out?

 

Steve

 

 

[murphy]

Electricity costs me about $0.005 per kWh so I've not given it any thought.  Solar panels were the best investment I ever made.  It's not one of those rent your roof to some company deals.  I own them outright.

[zimm25]

I have solar thermal, but solar electric isn't an option with my roof/trees. 

[meyersnole]

I'm sure some of the smart owners out there have figured this out, but at what price point does it make it more cost effective to run on gas alone?  Obviously the variable is electric price, but there must be a fairly simple calculation that can be made.  As Connecticut electric rates climbed 30% over the past 3 years ($0.20/kwh) and gas prices have fallen, the cost savings has to be very minimal at this point.  

 

Additional considerations must be:

 

1)  Charging efficiency - particularly on hot days when the battery pack has to be cooled.   

2)  Battery efficiency - a) as the battery gets older AND b) as winter temperatures decrease efficiency.

 

I love driving in electric mode and think it's better to use the battery rather than petroleum products, but I'm curious about the true costs balance.

 

Anyone figured this out?

 

Steve

 

 

As you mention, there are so many variables that a calculation would need to be set up for how you drive your car to answer that question. There are also many more factors you would need to consider. How you drive the car would be significantly more important than charging efficiency. Do you drive mostly secondary roads or freeways at high speeds?

 

Couple threads you might want to digest if want to understand how to calculate:

 

First one is pretty easy to digest: EV gas mileage vs gas mileage  http://www.fordfusionenergiforum.com/topic/2265-ev-mileage-vs-gas-mileage/?p=14639

 

These might make you a little crazy (So much information in these topics. There are more, but these two probable cover any question you might have and are very technical. ): 

Cold Weather Observations: http://www.fordfusionenergiforum.com/topic/1446-cold-weather-observations/?p=8941

OBD II Data for HVB http://www.fordfusionenergiforum.com/topic/1683-obd-ii-data-for-hvb/?p=10668

 

Also wanted to add it is nice living in a place that has cheap energy costs. 9.3697¢ /kWh  

Edited August 22, 2015 at 05:58 PM by meyersnole

[zimm25]

You're right that running in electric mode highway vs. secondary would make a big difference too.  I sit in a pretty good spot on rural secondary roads that average 40-50 mph with just 6 stoplights on my 18-mile commute.  

 

Electricity was a lot better until the February rate hike.  I still don't feel horrible about the price increase because it's 100% renewable.  There are many costs to living in the Northeast, but I love it here nonetheless.  

[jeff_h]

I've always thought of this is a "factor of 12" using the below rough estimates.  There are many variables so I only use this as a roundabout figure, so when I note 20 miles per charge, nobody needs to chime in with how they always get 25 or 28 or whatever... in good weather you get great range, in really hot or cold weather you get far less since the HVAC is used...

 

So just go with 20 miles for EV ranges and the other roundabout numbers below (or customize with your own numbers), and have a coke and a smile.

 

Full charge = 20 miles range

 

20 miles = 1/2 gallon fuel @ 40 MPG (of course some get better, some worse, it's only an estimate)

 

Full charge = 6 kWh * Electric rate $.010 per kWh = $0.60

 

Full charge = $0.60 = 1/2 gallon fuel

 

$0.60 for 1/2 gallon fuel x 2 = $1.20 per gallon Gas Price

 

Gas Price $1.20 / Electricity rate $0.10 = *12*

 

So with electricity cost of $0.20 per kWh, that would equate to roughly $2.40 per gallon (or electricity rate x 12)

Edited August 22, 2015 at 07:48 PM by jeff_h

[stevedebi]

I'm sure some of the smart owners out there have figured this out, but at what price point does it make it more cost effective to run on gas alone?  Obviously the variable is electric price, but there must be a fairly simple calculation that can be made.  As Connecticut electric rates climbed 30% over the past 3 years ($0.20/kwh) and gas prices have fallen, the cost savings has to be very minimal at this point.  

 

Additional considerations must be:

 

1)  Charging efficiency - particularly on hot days when the battery pack has to be cooled.   

2)  Battery efficiency - a) as the battery gets older AND b) as winter temperatures decrease efficiency.

 

I love driving in electric mode and think it's better to use the battery rather than petroleum products, but I'm curious about the true costs balance.

 

Anyone figured this out?

 

Steve

I use a simple formula: if the MPGe gets below what I can achieve when driving in hybrid mode, then theoretically it is better not to charge. In my case that is about 50 MPGe (I can generally get that around town). I'm currently at around 65 MPGe lifetime, and the only time I've come close to 50 is on a road trip, which doesn't really count.

 

For MPGe, I use the energy value that is on the trip meters, divide that by the amount of energy that is equivilent to a gallon of gas (33.7 KW hours = one gallon of gas). Then I add that number of gallons to the actual gallons I put in the car before dividing it into the mileage. This renders MPGe. I keep track of both MPG and MPGe.

 

Note that MFM will show MPGe, but it doesn't store the numbers for very long.

 

Driving a C-Max Energi here.

Edited August 24, 2015 at 05:20 PM by stevedebi

[flyingcheesehead]

I'm sure some of the smart owners out there have figured this out, but at what price point does it make it more cost effective to run on gas alone?  Obviously the variable is electric price, but there must be a fairly simple calculation that can be made.  As Connecticut electric rates climbed 30% over the past 3 years ($0.20/kwh) and gas prices have fallen, the cost savings has to be very minimal at this point.  

 

Additional considerations must be:

 

1)  Charging efficiency - particularly on hot days when the battery pack has to be cooled.   

2)  Battery efficiency - a) as the battery gets older AND b) as winter temperatures decrease efficiency.

 

I love driving in electric mode and think it's better to use the battery rather than petroleum products, but I'm curious about the true costs balance.

 

Anyone figured this out?

 

Steve

 

 

So, let's ignore the less significant variables such as the cost of oil changes and other ICE maintenance increasing, and focus solely on the energy costs.

 

Since battery range will change over time and also between seasons, you'll want to re-do this calculation every 3-4 months and any time gas or electric prices change significantly.

 

Use this formula:

(6.08 * E * H) / (B * C)

 

Where:

B = Battery range in miles. This is about 25 miles for me right now. 

H = MPG in hybrid mode (after HVB is depleted or in EV Later mode - I figure 38 in winter, 42 in summer)

E = Cost in dollar$ per kWh of electricity (I pay about 0.13/kWh)

C = Charging efficiency. This should be 0.82 if you're using an L2 (220V) EVSE, 0.72 if you're using an L1 (120V) EVSE like the one included with the car, based on LarryH's measurements.

 

The result of the formula is the equivalent fuel price. If you can get gas cheaper than the result of the formula, then you'll spend less burning gas. If they're close, I'd still favor electricity because it's cleaner, quieter, and should result in lower maintenance costs.

 

For the math-lazy, here's a spreadsheet so you can just plug in your numbers. Enjoy. Fusion Energi Equivalent Fuel Price.zip

[Hybridbear]

Use this formula:

(6.08 * E * H) / (B * C)

 

Where:

B = Battery range in miles. This is about 25 miles for me right now. 

H = MPG in hybrid mode (after HVB is depleted or in EV Later mode - I figure 38 in winter, 42 in summer)

E = Cost in dollar$ per kWh of electricity (I pay about 0.13/kWh)

C = Charging efficiency. This should be 0.82 if you're using an L2 (220V) EVSE, 0.72 if you're using an L1 (120V) EVSE like the one included with the car, based on LarryH's measurements.

 

The result of the formula is the equivalent fuel price. If you can get gas cheaper than the result of the formula, then you'll spend less burning gas. If they're close, I'd still favor electricity because it's cleaner, quieter, and should result in lower maintenance costs.

Very cool formula. I just plugged in my numbers:

• B = 26
• H = 50 (back when we had our FFH I could get 50 MPG pretty consistently in the summer)
• E = $0.11 (this is the approximation we use to calculate the $40 flat rate we pay per month to our apartment)
• C = 0.82
• Result: $1.57/gal

We actually pay less for gas than that usually since we buy gas so rarely & we thus can accumulate about $1.50/gal in fuel rewards from a local grocery chain. However, if we were buying gas all the time we'd only be saving a few cents off of the published price/gal so it wouldn't actually be cheaper to run on gas.

[flyingcheesehead]

Very cool formula. I just plugged in my numbers:

• B = 26
• H = 50 (back when we had our FFH I could get 50 MPG pretty consistently in the summer)
• E = $0.11 (this is the approximation we use to calculate the $40 flat rate we pay per month to our apartment)
• C = 0.82
• Result: $1.57/gal

We actually pay less for gas than that usually since we buy gas so rarely & we thus can accumulate about $1.50/gal in fuel rewards from a local grocery chain. However, if we were buying gas all the time we'd only be saving a few cents off of the published price/gal so it wouldn't actually be cheaper to run on gas.

 

Nice! You're better than me on all four variables! My equivalent gas prices is $1.84/gal right now. Would have been about $2.49/gal in midwinter! :o

[openair]

 

I use a simple formula: if the MPGe gets below what I can achieve when driving in hybrid mode, then theoretically it is better not to charge.

 

As this doesn't consider $ at all it doesn't really relate to the op.  Just converting kwh to gallons without factoring in what each cost and the variation in those costs is meaningless in the context of the op.

 

 

Use this formula:

(6.08 * E * H) / (B * C)

 

 

Can you explain where you get 6.08 from?  It's difficult to understand how this formula arrives at a meaningful number without knowing what 6.08 signifies.

Edited August 25, 2015 at 03:54 AM by openair

[Automate]

Can you explain where you get 6.08 from?  It's difficult to understand how this formula arrives at a meaningful number without knowing what 6.08 signifies.

 

 

Looks like kWH per battery charge.  The Ford specs are 7.6kWH.  Maybe 7.6kWH minus the 1.4kWH hybrid reserve?  If your battery is older and does not have full capacity you would need to adjust this number.  But you would probably also have to adjust the C number since an older battery probably does not have the same charging efficiency as a new battery.

Edited August 25, 2015 at 12:22 PM by Automate

[Timewellspent]

Looks like kWH per battery charge.  The Ford specs are 7.6kWH.  Maybe 7.6kWH minus the 1.4kWH hybrid reserve?  If your battery is older and does not have full capacity you would need to adjust this number.  But you would probably also have to adjust the C number since an older battery probably does not have the same charging efficiency as a new battery.

 

That number has me confused as well.  When I look at MFM and see I used the full battery on a trip it shows I used 5.5 kWh.  How can my 2015 car be so much lower?

[openair]

That number has me confused as well. When I look at MFM and see I used the full battery on a trip it shows I used 5.5 kWh. How can my 2015 car be so much lower?

My 2014 has always been between 5.4 and 5.8 kwh. If this number is just kwh it should become a variable like all the others in the formula has kwh can change with the life of the battery or maybe you want to factor in some preconditioning or use this formula for a vehicle other than a ford energi.

 

Also, if 6.08 is just kwh or includes kwh (which it must), than listing the formula as...

 

kwh / C * E * H / B

 

Removes the need for brackets and makes the formula progression and arrival at a meaningful number easier to understand

Edited August 25, 2015 at 09:43 PM by openair

[larryh]

The car does not charge the HVB to capacity.  It only charges it to a maximum of 7.2 kWh.  It usually charges the car to 98% of capacity.  The car does not allow you to discharge the HVB below 1.0 kWh.  So about the most you will get out of the HVB is about 6.0 kWh.

 

The car does not charge the HVB to capacity or complete discharge it to prolong the life of the HVB. 

Edited August 25, 2015 at 09:13 PM by larryh

[flyingcheesehead]

Can you explain where you get 6.08 from?  It's difficult to understand how this formula arrives at a meaningful number without knowing what 6.08 signifies.

 

 

7.6kWh * 80%. Explanation below.

 

Looks like kWH per battery charge.  The Ford specs are 7.6kWH.  Maybe 7.6kWH minus the 1.4kWH hybrid reserve?

 

Battery is 7.6 kWh, but "empty" for the HVB is essentially 20% (Larry explains why below). In reality, this could be anywhere between 15%-22%, and probably at the lower end of that if using EV+. But, 6.08 is a reasonable estimate of the capacity that's actually being used. If you're one of the people who's actually paying attention to how much energy is being stored in your particular battery, you could change the 6.08 to whatever is appropriate in your situation. 

 

The car does not charge the HVB to capacity.  It only charges it to a maximum of 7.2 kWh.  It usually charges the car to 98% of capacity.  The car does not allow you to discharge the HVB below 1.0 kWh.  So about the most you will get out of the HVB is about 6.0 kWh.

[Hybridbear]

We usually start at about 7.077 kWh ETE. At least, this is our average over the past 118 full charges that I have recorded to measure HVB capacity loss. The lowest we've ever ended a trip with was about 1.11 kWh. That would give us a maximum of about 5.97 kWh for the calculation, instead of 6.08.

[bdginmo]

Ok, so a full charge is roughly 6 kWH into the HVB. How much energy actually comes out of the wall though?

Edited August 27, 2015 at 03:56 AM by bdginmo

[JATR4]

Ok, so a full charge is roughly 6 kWH into the HVB. How much energy actually comes out of the wall though?

As stated above that is the efficiency calculation which is "C" in the calculation.  Use 0.82 (L2) or 0.72 (L1). 

 

From above:

 

"C = Charging efficiency. This should be 0.82 if you're using an L2 (220V) EVSE, 0.72 if you're using an L1 (120V) EVSE like the one included with the car, based on LarryH's measurements."

 

The out of the wall values are approx 7.32 and 8.33.

Edited August 27, 2015 at 04:59 AM by JATR4

[lonzo71]

So, let's ignore the less significant variables such as the cost of oil changes and other ICE maintenance increasing, and focus solely on the energy costs.

 

Since battery range will change over time and also between seasons, you'll want to re-do this calculation every 3-4 months and any time gas or electric prices change significantly.

 

Use this formula:

(6.08 * E * H) / (B * C)

 

Where:

B = Battery range in miles. This is about 25 miles for me right now. 

H = MPG in hybrid mode (after HVB is depleted or in EV Later mode - I figure 38 in winter, 42 in summer)

E = Cost in dollar$ per kWh of electricity (I pay about 0.13/kWh)

C = Charging efficiency. This should be 0.82 if you're using an L2 (220V) EVSE, 0.72 if you're using an L1 (120V) EVSE like the one included with the car, based on LarryH's measurements.

 

The result of the formula is the equivalent fuel price. If you can get gas cheaper than the result of the formula, then you'll spend less burning gas. If they're close, I'd still favor electricity because it's cleaner, quieter, and should result in lower maintenance costs.

 

For the math-lazy, here's a spreadsheet so you can just plug in your numbers. Enjoy. Fusion Energi Equivalent Fuel Price.zip

Ok...so I used the form and here are my numbers...

 

B  31

H 42

E 0.08399

C 0.82

 

Equivalent fuel price $0.844/ Gal

 

Just doesnt look right...lol

[JATR4]

Ok...so I used the form and here are my numbers...

 

B  31

H 42

E 0.08399

C 0.82

 

Equivalent fuel price $0.844/ Gal

 

Just doesnt look right...lol

Your B is pretty high and your E is pretty low  which makes your calculation very low.  My numbers are:

 

B  20

H  44

E  0.11

C  0.82

 

Calculates to $1.79.  I am only paying $2 now so getting close. 

[lonzo71]

Your B is pretty high and your E is pretty low  which makes your calculation very low.  My numbers are:

 

B  20

H  44

E  0.11

C  0.82

 

Calculates to $1.79.  I am only paying $2 now so getting close. 

Well, the B, i'm went with what the car says right now...and E was based on what I pay for Generation. I should have added the total which is about 11 cents( 0.11507)..(tho you could argue that one should add the taxes/surcharges and the rest). 

The total is now $1.156

 

Added to say; We have cheap power, sadly, Pepco adds so many taxes and surcharges that my total could go over 4 bucks a gal

Edited August 27, 2015 at 06:31 PM by lonzo71

[lonzo71]

ok..figuring the power company numbers and all...and just stopping cause I hate trying to figure everything out..so I'll just use E as .18 which gives me a total of $1.808...

 

I'm still buying gas at 2.60ish...So I have a ways to go...

[bdginmo]

As stated above that is the efficiency calculation which is "C" in the calculation.  Use 0.82 (L2) or 0.72 (L1). 

 

From above:

 

"C = Charging efficiency. This should be 0.82 if you're using an L2 (220V) EVSE, 0.72 if you're using an L1 (120V) EVSE like the one included with the car, based on LarryH's measurements."

 

The out of the wall values are approx 7.32 and 8.33.

 

Ugg...sorry. I have no idea I how I missed that. Anyway, I have a spreadsheet that does a little more elaborate calculation and is dynamic based on different price points for energy throughout the year and what MPG and EV range I can expect. I plugged 0.72 into my formulas.

 

Full charge = 6.08 kwH / 0.72 = 8.44

Winter electricity rate = 0.0579 / kWH (October - May)

Summer electricity rate = 0.1218 / kWH (June - September)

Winter gasoline rate = 2.25 / gallon

Summer gasoline rate = 2.50 / gallon

Winter hybrid MPG = 40

Summer hybrid MPG = 50

Winter miles per charge = 10

Summer miles per charge = 20

Miles driven per year = 21000

 

Based on the above with my personal driving habits my breakeven on EV vs. GAS would be if gas were $1.95/gallon. I've only had my 2015 FFE for a month now so my EV range and hybrid MPG may be a bit off.

 

I estimated that I am saving $800/year in energy costs. I should easily make up for the added cost of the vehicle relative to a similarly equipment standard gasoline Fusion. Plus, it's fun to drive!

Edited August 30, 2015 at 03:52 PM by bdginmo

[Energized]

B = 25

H = 45

E = 0.32

C = 0.72

 

$4.864

 

 

For me, its always been cheaper to use gasoline.

Edited August 30, 2015 at 11:43 PM by Energized