# Which is harder on the power grid: a winter cold spell, or summer heat wave?

Just a wonder of mine, as I sit here listening to my heat pump struggle to maintain.

For the Q, assume the North East USA.

I think Summer heat waves are more difficult for the grid due to A/C load combined with the complications heat brings to power distribution systems.

I'm guessing that even an extreme winter cold spell is probably easier on the grid than summer heat--I assume this due to: furnaces are more likely installed in climate zones where electric powered heat pumps are poorly suited (heat pumps being a poor choice in areas with frequent low temps).

In other words:

Sumer Heat Wave

• everyone running A/C
• plus distribution issues

Winter Cold Spell

• most running furnaces (electric operated, but other heat source)
• some with heat pumps within their limits
• fewer with heat pumps inefficiently operating beyond spec

I think a heat wave is more difficult for the grid.

• To cool our planet you need approximately 5 times the energy that is required to heat it. – GR Tech Feb 16 '15 at 12:25
• @GRTech how would you cool our planet with energy? where would it go? into space? or would you transform it into matter? – user2813274 Feb 16 '15 at 16:59
• Can you expand on the "issues" hot weather brings to distribution systems? In my experience winter conditions are far harder on any sort of distribution grid in most places: frozen equipment/buildings, ice/snow build up bringing cables down or blocking things up, wind, rain, flooding / water ingress, falling trees / poles, difficulty of access for repair especially in remote areas, lightning strikes, etc. etc. – John U Feb 16 '15 at 17:10
• I'm aware of high heat causing lines to sag which causes issues. But I'll take your experience over my own. – Paulb Feb 16 '15 at 18:58

You don't define what you mean by "harder". In New England, the hardest time on the grid is in deep winter. The region is summer-peaking in terms of electricity demand, but political and structural problems cause the cost of electricity to go much higher in winter.

The basic problem is that the supply of natural gas into New England is limited, natural gas is a major fuel for winter heating, and by law residential heating customers get first dibs on the limited supply. This means commercial electric power plants can't use natural gas as a fuel on cold winter days because there simply isn't enough of it.

The bottleneck isn't the overall supply of natural gas. Plenty is being produced in North America due to fracking technology. The problem is getting this abundance into New England in sufficient volume. The existing pipelines are too small for the demand on a cold winter day. Years ago before the fracking boom, liquified natural gas terminals were built in Everret MA and someplace in New Brunswick or Nova Scotia (sorry, don't remember the details). More pipeline capacity overland was not built because there wasn't any excess gas in the rest of the continent to get.

Now with the technology advances that allow extracting vast quanties of natural gas from places like the Bakken formation (more oil than all of Saudi Arabia, but a lot harder to extract) and others in North America, there is suddenly a glut of natural gas at the other end of a thin straw from New England. When available, this gas is much cheaper than LNG brought in by ships. Also, LNG has to be planned on ahead of time, whereas with a pipeline you just turn on the spigot.

Despite a unusually cold last winter, none of the electric producers took the risk to order ahead the available but more expensive LNG. By the time it's cold, it's too late to arrange for a ship to show up in time. A contributor to this is that ISO-NE (the quasi-government agency that oversees the power grid here) discouraged commercial electric generators from arranging LNG. This may sound backwards, but they want new pipeline capacity built, and want to deliberately create more of a crisis than necessary to get the public to support the new pipelines.

My town has a municipal electric company, as apposed to being served by one of the large investor-owned utilities like NSTAR and National Grid. Up until this year, we kept the price constant over the year. This meant we lost money in the winter and made it up in the summer. Last spring, "strips" (wholesale blocks of electricity contracted ahead of time) for January 2015 were selling for $.18/kWh, which is considerably more than our electric department sells it back to consumers. The spot market fluctuates much more widely, and last year hit much higher prices than$.18/kWh during peak demand times when the temperature was low.

This high winter price is solely due to unavailability of natural gas. Some producers have to shut down when there is less gas, and others switch to more expensive oil. Note that the expense here isn't just the oil, but the regulatory cost of burning more carbon to get the same energy. In summer, the wholesale cost is more like \$.05/kWh or so, even during peak electric demand that exceeds the peak electric demand during winter.

But wait, it's even more messy than this. Generation capacity is actually being reduced in New England. The coal/oil plant at Salem Harbor has already been shut down, and the large coal burning plant at Brayton Point is scheduled to be shut down. These were done for environmental reasons, or more accurately, higher costs created by environmental regulations aimed at reducing carbon emissions. That may make some sense, but the generating capacity is not being replaced.

Not only are some large carbon-spewing plants being retired, but incredibly, the Vermont Yankee nuclear plant also. This plant was functioning perfectly well, and of course wasn't producing carbon emissions. Other regulations made it too costly to keep operating to the point where the owners decided that shutting it down was the best choice economically.

Yes, this whole issue is quite a mess, with lots of different groups pulling in different directions with different purposes.

• Wow.. what a regulation mess. Seems like some law makers need to better understand the law of unintended consequences. – Paulb Feb 16 '15 at 16:13
• "the large coil burning plant " ... poor coils, what did they do? Or is this a new way to get the last bit of energy in high efficient buck converters? – PlasmaHH Feb 16 '15 at 17:05
• @Plasma: Fixed. – Olin Lathrop Feb 16 '15 at 17:14
• VT Yankee won there long fought court battle, but then shut down voluntarily anyway. I'd like to see it replaced with a new reactor, but I seriously doubt many of the locals will get behind that idea. – kevingreen Feb 16 '15 at 17:18
• @kevin: There is no real physical reason VT Yankee needs to shut down. Unfortunately there are a few legislators in the state of Vermont that just don't like nukes, and they do whatever they can to make things difficult, and therefore expensive, for VT Yankee to operate. Since and technology and careful engineering decision making have nothing to do with it. It's a religious issue, and the religious zeleots won out this time. – Olin Lathrop Feb 16 '15 at 19:21

Question is meaningless without a location : a heatwave made my local paper when the temperature exceeded 80F (27C?) for a few days. Almost nobody round here has AC. You might get different answers in Scotland and Arizona...

Hardest on the Grid in the UK is half time during the Cup Final when about a million 2.5 kw kettles are switched on at once. Fortunately the Cup Final is advertised well in advance.

• 80°F a heat wave? Right now it is the middle of winter and it will be over 80°F here several days this week. Yes I am in AZ. Back in 2011 we had a month with every day over 110°F -- that's a heat wave. 115°F is not uncommon. We pay for it every summer on electric bill -- AC pretty much running continuously. – tcrosley Feb 16 '15 at 16:59
• @tcrosley - In Scotland, any time it's not driving freezing sleet up your nose counts as a heatwave. – John U Feb 16 '15 at 17:07
• @tcrosley ... John U exaggerates ... slightly. I taunted my colleagues in Texas with that newspaper report! – Brian Drummond Feb 16 '15 at 17:45
• Talking about "heatwave made my local paper" and "around here" without equally meaningless without a location. You don't say where you are referring to, and you haven't filled in your location in your profile (remember that good profile information is a courtesey to us, not really for you). – Olin Lathrop Feb 17 '15 at 23:28
• @Olin : As to the approximate location, John U figured it out. On that occasion, the Isle of Skye to be precise. – Brian Drummond Feb 18 '15 at 11:27

Anecdotal data point from Europe: Until circa 2008, the winter peak load was higher than summer peak load. Unfortunately, I can't find the source anymore.

• This doesn't explain which is more stressful for the grid. – sharptooth Feb 16 '15 at 11:58

Another not-quite answer from the UK: have a look at the excellent live power tracker http://www.gridwatch.templar.co.uk/ Their annual history graph is rather small, but its peak seems to be in January.

The east US large blackout seems to have resulted from a combination of heat and software failure.

• The power tracker was interesting. – Paulb Feb 16 '15 at 13:10

I am in Ontario, Canada, close to NE USA. Here the government jacked up electricity cost, most people switched to natural gas for heating.

For this reason here the highest demand is in the summer during heat waves. Winter high demand peaks are very close to the summer.

In Ontario, the government installed smart meters, and introduced time of use rates. Cheaper at night, highest during a day. It didn't make a big difference in consumption or the peak times.

In Ontario, the consumption of electricity is not increasing, because of reduced use of incandescent light bulbs, and many businesses and industries have shut down and left. One of the reasons for them to leave was high cost of electricity.

• I remember when low cost electricity from Niagara Falls gave Ontario a competitive advantage. It was also an export product. Sorry that isn't the case anymore. – Paulb Feb 16 '15 at 15:44