What Time of Day/Night Should I Charge for Smallest Carbon Footprint?

[⚡️ELECTROMAN⚡️]

I was thinking it was during off peak hours, but then again maybe it's during the day, when solar power is being produced. This could very well be true for a Californian, but I live in Oregon. I would guess the answer is very complicated, and depends on where you live, but I was wondering if anyone could offer the community some insight.

 

[S'toon]

Green Source - Renewable Power | PGE

 

[Mickie]

I do 2AM personally.

 

[AEdennis]

I was thinking it was during off peak hours, but then again maybe it's during the day, when solar power is being produced. This could very well be true for a Californian, but I live in Oregon. I would guess the answer is very complicated, and depends on where you live, but I was wondering if anyone could offer the community some insight.

Check out Wattime... they did a presentation with eMotorwerks a couple of years ago... not sure if they still have his partnership, but the mission of Wattime is what you were pondering.

 

[sillydriver]

Interesting question! I suppose it's a matter of the carbon intensity, at any time of day, of an incremental or marginal kW of demand from charging. In most of the country I think the peak load is generated by natural gas fired plants whose carbon intensity is not too bad. If those peaking plants are off during the middle of the night, so incremental demand from nighttime charging is provided only by the base load generating capacity, then if the base load capacity is hydro or nuclear, nighttime charging is very low-carbon and better than daytime natural gas; however, if the base load plants are coal, nighttime is high-carbon and worse than daytime natural gas.

Having solar generation during the day complicates things, but only if solar is truly serving the marginal kW of demand. If solar is producing at full capacity whether or not you are charging (which it probably is, because the marginal cost of solar power production is zero), while your marginal demand is served by throttling gas-fired peaking plants, then the calculation is the same as before. Thus the existence of solar generation during the day doesn't necessarily make it lower carbon (on an incremental basis, which is what I think matters) to charge during the day.

 

[kort677]

I was thinking it was during off peak hours, but then again maybe it's during the day, when solar power is being produced. This could very well be true for a Californian, but I live in Oregon. I would guess the answer is very complicated, and depends on where you live, but I was wondering if anyone could offer the community some insight.

the "footprint" doesn't vary by time of day, much of power generation cycle causes the same levels of pollution regardless of when it is generated.

 

[Topher]

the "footprint" doesn't vary by time of day,

The footprint varies quite a lot by time of day.

But that doesn't really answer the real question, which is how much will charging now, as opposed to later CHANGE the carbon footprint of the electricity generation.
Simple method: Charge when it is cheap. I have an app (ISO to go, works for New England) which gives the spot price for electricity at the moment.
Complicated method: Get access to the current state of the grid, will adding a bit more need cause them to fire up a peaking plant? Are they cutting back power from renewables? Are they at a transition point for a coal plant?

Thank you kindly.

 

[kort677]

The footprint varies quite a lot by time of day.

But that doesn't really answer the real question, which is how much will charging now, as opposed to later CHANGE the carbon footprint of the electricity generation.
Simple method: Charge when it is cheap. I have an app (ISO to go, works for New England) which gives the spot price for electricity at the moment.
Complicated method: Get access to the current state of the grid, will adding a bit more need cause them to fire up a peaking plant? Are they cutting back power from renewables? Are they at a transition point for a coal plant?

Thank you kindly.

you are correct that trying to predict when peak demand is would be difficult.
the only time the OPs concerns would be in play would be at times of extreme demand as older, less efficient sources are brought online to meet the demand.
in most parts of the country this isn't a regular occurrence because of grid interconnectivity.
I know that TX is almost an island with connectivity and I suppose much of CA is not part of an integrated grid, so in those places his concerns might be warranted, in most of the rest of the country the origin of the power generation shouldn't vary much be it hydro, nuclear, nat. gas, fuel oils and to a much lesser extent coal.

 

[KArnold]

FWIW here in central Ohio we cannot get metered rates. In other words I pay the same rate regardless of time of day. That honestly seems a bit silly to me but it is highly regulated - to offer a different rate requires a ton of red tape.

 

[LuPapa]

I was thinking it was during off peak hours, but then again maybe it's during the day, when solar power is being produced. This could very well be true for a Californian, but I live in Oregon. I would guess the answer is very complicated, and depends on where you live, but I was wondering if anyone could offer the community some insight.

Since you live in Oregon you should look at the state electric mix.
State of Oregon: Energy in Oregon - Electricity Mix in Oregon

Major electrical is
42% hydro
33% coal
13% natural gas

Hydro plants run all day. Coal plants are base load and will be run all day as well. Some of that natural gas will get shut down overnight.

That large hydro percentage is great. you could be more green if you added solar to your roof. But your mix is better than most states which use a lot more coal and natural gas.

 

[SageBrush]

Simple method: Charge when it is cheap.

Hi Topher,

Why does cheap equal low marginal emissions ?

OP: you are right -- it is very much a local question. You might have some luck scouring your utility website and talking to local people with a similar interest. For a lot of the country, NG makes up the margin during the day and coal is king at night but that is very YMMV.

 

[Topher]

Why does cheap equal low marginal emissions ?

It doesn't, it is an approximation. Cheap means that 1) The grid is in surplus, so it is likely that they have shut down some easy sources, wind and hydro being primary amongst those (and cheap). 2) Base load sources are not likely to be changing. 3) Generally new low emission sources are cheaper.

Thank you kindly

 

[kort677]

3) Generally new low emission sources are cheaper.

Thank you kindly

I guess our local utility didn't get the memo
SolarSmart | Rates | Understand My Bill | My Account | JEA

 

[brucet999]

Hi Topher,

Why does cheap equal low marginal emissions ?

Probably doesn't, but here in extortionate-rates Southern California Edison land, middle of the night rates are $0.125/kWh, whereas peak rates are three times as much.

 

[SageBrush]

Cheap means that 1) The grid is in surplus, so it is likely that they have shut down some easy sources, wind and hydro being primary amongst those (and cheap). 2) Base load sources are not likely to be changing. 3) Generally new low emission sources are cheaper.

Hmm. If I was inclined to generalize I would say cheap = coal, although wind can certainly be very cheap too.

 

[Topher]

If I was inclined to generalize I would say cheap = coal,

Have you looked up the prices recently?

Thank you kindly.

 

[SageBrush]

Have you looked up the prices recently?

Nope, so I did now:

Coal Markets

One million btu is 293 kWh, so wholesale coal is ~ 0.5 cents a kWh average and a range of 0.25 - 0.93 cents a kWh if I am reading the table correctly. If we figure coal plants are 33% efficient, then coal based wholesale electricity would work out to 0.75 - 2.8 cents a kWh.

Am I misunderstanding ?

 

[johnr]

In California you can see real-time power mix and renewables percentage at California ISO - Todays Outlook
I don't know about Oregon though, sorry.

The fact is, though, it's very rare when renewables supply anything close to 100% of the mix, so if you schedule your charging for when renewables are a high percentage, that just means somebody else is taking a little more nonrenewables instead of you. Seems pointless in the end, as you're still not able to increase the amount of renewable energy being generated. The only way this actually changes anything is if renewables are near 100% and would go to waste if you didn't use it. At least that's my two cents.

Now there are a handful of standalone solar powered charging stations popping up in various places - if there's one in your area, by all means use it, and you're guaranteed 100% solar charging! Here's an example of one in my neighborhood: Reedley City Hall | Reedley, CA | Electric Car Charging Station | PlugShare

 

[SageBrush]

The fact is, though, it's very rare when renewables supply anything close to 100% of the mix, so if you schedule your charging for when renewables are a high percentage, that just means somebody else is taking a little more nonrenewables instead of you

There are now three of us to my knowledge who make this point.

However, there are a couple of subtleties to consider:

Utilities run the least expensive base-load they can find and supplement as needed with (usually) more expensive NG and renewables. So the trick is sometimes to find out when the renewables are on-line in your locale and charge then to avoid curtailment.

 

[dhrivnak]

Charge during the day AFTER you get your solar roof. It is 100% clean power that you can control