Peak vs Off Peak Electricity Hours

March 15, 2009 12:10 PM

How much can I save by using off peak electricity in the US? How does this compare to those in Europe?

I realize that not many utilities in the states offer off peak hours but i know some do. What percent do some of you save by using this option?

My google fu has failed and i am only getting really skimpy results.

Can anyone find the how much free energy we are loosing (hydro/wind/thermal) because it is being produced but not used?

posted by Black_Umbrella to work & money (6 answers total)

It will vary a lot by region, season, and what the marginal fuel and generating units are in that region.

Today, at PJM-RTO (Pennsylvania-Jersey-Maryland) (ro, you pay $27/mWh in the dead of night, but $45/mWh at a peak, but it's the weekend so a lot of office buildings aren't using much power. By contrast, in the middle of August, you'll still pay around $30/mWh at 3am, but it is up to $90/mWh by 4pm or 5pm.

Europe is about €30/mWh in the dead of night, and €50-60/mWh at peak.
posted by milkrate at 12:42 PM on March 15, 2009

I have saved a fair bit in the past without trying, but it was mainly from a lifestyle that happened to correspond to offpeak. If you keep fairly normal waking hours, you might not be able to take much advantage of it, other than things like purchasing night-store heater. OTOH, if you're able to run your dryer and dishwasher, etc. late at night, and have showers before bed (so the bulk of the water heating happens off-peak), you would still see some benefit.

Can anyone find the how much free energy we are loosing (hydro/wind/thermal) because it is being produced but not used?

None. That's not how the grid works. Electricity, once produced, can't be stored, so electricity is produced when it is needed in the quantity that is needed, in an unending balancing act. In a hydro station for example, there are mechanisms that can rapidly scale up or down the amount of water passing through the turbines, and thus adjust the energy output to match current demand.
Wind turbines aren't as adjustable without losing power, but even when demand is at minimum, wind turbines are not producing anything close to demand, so they don't need to scale - the hydro-station can just scale down it's throughput a bit more, which is perfect since wind not used for generating isn't stored, but water not used for generating remains in the lake, stored energy.
posted by -harlequin- at 1:51 PM on March 15, 2009

harlequin, i guess what i am getting at for the renewable is what if you did not scale back the energy generation. That makes sense the a resivoir can be filled which would not produce electricity. But i have been to a few small hydro plants on kauai...and believe me, they did not have much in terms of electronic control. I highly doubt these small turbines / reservoirs had proper mechanisms to contain the water to the correct point. Literally all the mechanicsms were manually controlled screw valves. So there must been a large number of these small plants which are producing waste energy. The same with wind/thermal, why would you ever scale back the production of energy?
posted by Black_Umbrella at 4:40 PM on March 15, 2009

Black_Umbrella, I'm not quite sure what you mean in your reply to harlequin, but it's important to understand that there are several types of power plants in most generation schemes, roughly organized into base load, shoulder load, and peaking load.

Base load is generation that is always on, and the amount of base load generated in a regional network will be at a much lower level than that areas peak daily and seasonal load. As load increases during the day or between seasons, shoulder and peaking load is brought into play. Peak hours cost so much partially/possibly because of regulatory and industry schemes to deter peak usage, but mostly because peak generation tends to be comparatively inefficient and expensive.

Base load is usually coal, nuclear, or natural gas fueled generation using technology that is relatively efficient but cannot be dead started and stopped easily. Shoulder and peaking load uses quick-start, less efficient technology such as a gas turbine, an enormous fucking diesel engine (which may be parted out from a WWII submarine in some Midwestern municipalities), or something similar. Shoulder and Peak load has to be able to start and turn off quickly, or else these less efficient and more expensive to fuel technologies would not be used. I'm not entirely sure where hydro fits into this scheme; my experience with the regulatory environment comes from doing energy policy research for the state of Kansas.

Wind and solar are somewhat difficult to fit into this scheme due to the predictability issues. A utility systems engineer once told me that the next great advance in computing/AI will probably be driven by the difficulties of dispatching power within networks largely powered by solar and wind generators. Made sense to me.

Electricity, once produced, can be stored as some sort of energy if you want to do so. Or you can use your generators to create some sort of energy store rather than dispatching electricity in the first place. You can then dispatch your stored energy as electricity when you need to. This is currently done on a relatively small scale; large (really large!) capacitors are connected to most large electrical grids at various points so that sharp spikes in demand don't drive down system voltage. In general, though, energy storage is expensive and introduces further system inefficiency. However, the expanding renewable sector is creating a lot of interest in storing generation due to the dispatch considerations mentioned above. Schemes I have seen include artificial water reservoirs with hydroelectric generators, really big flywheels (sounds safe to me!), more big capacitors, and compression of air in huge tanks (boom!).

Anyways, to actually address part of your original question, the generation scheme in the U.S. and probably Europe does not operate so that enough generation to meet peak demand is always on. Rather, a baseline amount of generation is always on, and shoulder and peaking plants are brought on when necessary, as I explained above.
posted by Derive the Hamiltonian of... at 7:32 PM on March 15, 2009

Peak energy usage is ridiculously expensive. There are plants in Texas on the ERCOT grid that operate a few hours per year but carry the same fixed costs as any other, so they charge outlandish rates in the state's bidding system. According to the Wall Street Journal, in May 2008 prices in the Texas wholesale market hit $4 per kilowatt-hour. Considering that I'm on a $0.147 per kilowatt-hour price plan through my energy retailer, that's a HUGE price swing.

Here's the thing: You can only save money by shifting your usage if your utility supports it. Again, using Texas--which is the only model I know--we have no such "time of day" meters in large-scale deployment. Portions of the Oncor (TXU) service area are getting them according to media reports, but wide availability isn't scheduled to happen until 2010 at the earliest (who will pay for the meters? subscribers, of course). Right now, electricity costs me 14.7 cents/kwh regardless of if I'm washing clothes at 11:41PM CDT on March 14th (wait, I am!) or running the air conditioner at 2:38PM on July 9th. When/if these kinds of meters arrive, I predict an even bigger shaf--err, more savings--from our friendly electric retailers.
posted by fireoyster at 9:42 PM on March 15, 2009

Black Umbrella:
Tour a huge hydro station. Where they were intended to fit into the local scheme of things (base load or shoulder) will determine what they can do, but all the big hydro stations I've been in had the stuff in place to scale their output rapidly, whereas the small hydro stations were likely to be more cost efficient if it's just left alone, running at optimal rate to contribute a little piece to base load, requiring few or no round-the-clock staff.
posted by -harlequin- at 10:25 AM on March 18, 2009