Thursday, 15 March 2012

Smart meters will save us money, if we take advantage

The load on the electricity grid varies through the day. In January, the peak load is a bit over 50 GW at around 6pm whereas the minimum at around 6am is nearer 30 GW as you can see in the graph below.  The peak is a rise of about 5 GW from 3pm which is about 200W per house. As the days get longer in February and March the peak shifts later and lower.
2011: mean weekday demand: 1st week Jan, 1st week Feb, 1st week Mar [2]

This pattern is consistent and so predictable and can be allowed for but the shift away from fossil fuels will make this more expensive to achieve in future. We need to shift the loads to even out the peaks and troughs. At the moment some people have a dual tariff with lower costs overnight to encourage them to shift loads to off peak but you have to have a second meter and it is isn't easy to change. Smart meters will make more flexible tariffs possible and this should be greatly to our advantage.

For fossil fuel power stations the greater part of the cost of electricity is due to the cost of the fuel to drive the plant. Only about a third is fixed costs or capital cost. This means that you can run a gas or coal power station on standby or even shut it down without losing a huge amount of money. For nuclear power stations, most of the cost is in building them and the fuel costs very little [1].  Ramping the power output up and down wastes a lot of money. Running on half power the effective cost of the electricity from a nuclear power station rises by a third (see Nuclear Power isn't just for base load from 18/Jan/2012).

Similarly, almost all the cost of wind and solar power is up front capital costs and fixed costs. Leaving them idle is expensive. Also, we will need to maintain backup capability for when the wind isn't blowing and the sun isn't shining. This can be in the form of storage or backup generating capacity; either way it will cost money.

This means there will be at least two important ways in which load shifting will be useful:
  • to even out the peaks and troughs so that  we can run our plant at or near full power and not need lots of extra plant which is rarely used
  • to reduce load when the intermittent renewable sources are below optimal, so that less backup is needed
To some extent, we can expect the difference between the peaks and the troughs to reduce anyway as we use more efficient appliances. At least 20% of the peak load used to be due to lighting but low energy light bulbs and LEDs will reduce this [3]. For cooking, the latest induction hobs are a great deal more efficient than the traditional rings. However, our overall electricity consumption is going up not down, because of new appliances: more TVs, more computers, more games...

If increased efficiency doesn't do enough  to even out the peaks and troughs the energy companies are going to have to motivate us with some interesting tariffs. Peak time electricity will cost more, but off peak will cost less. Most of the time this will be predictable and, depending on how much nuclear power we use, it will be much the same from day to day. There are going to be lots of ingenious products on the market  to help us make use of this.

In fact if you have solar panels you are probably already doing some load shifting, to make use of the free electricity from your panels when it is available.

Here are some ways we can shift load from peak time, if we want to. Some need a little technology (like the new microprocessor controller just unveiled by ARM), others just require a little planning.
  • Run washing machines and dish washers on a timer, at off peak.
  • Reduce power consumption for freezers and refrigerators by letting them get a little bit warmer (ideally by dropping the temperature in advance when peak tariffs are expected soon; this needs new controllers). 
  • Charge your electric car off-peak (1 charge will be 15-30 kWh [4]).
  • Run your computer more slowly at peak times (lap tops usually run more slowly when you are not very busy so as to save the battery).
  • Use a slow cooker (which runs gently all day) rather than cooking your evening meal just before eating.
  • Get the children to do their homework in the early evening, saving their high power computer games for later.
In summary: flattening the peaks and troughs in demand will reduce generating costs with either nuclear power or renewables. Smart meters will make it possible for the electric companies to motivate us to do this and when they do this it won't be hard to take advantage and reduce our bills too. Bring on the smart meters!

[1] UK Electricity Generation Costs Update (DECC)
[2] Metered half-hour electricity demands (National Grid)
[3] 40% House (Environmental Change Institute, University of Oxford
[4] Battle of the Batteris, comparing electric car range, charge times

1 comment:

  1. However, there are potential concerns about smart meters too in particular privacy and security as described here. The meter software developers do need to think serously about this.