‘Baseload’ power and what it means for the future of renewables

By Glenn PlattFebruary 27th, 2018

In the new world order of mixed-source energy, trusty baseload power is often misunderstood. It's not just a question of what baseload can do for renewables, but what renewables can do for baseload power.
power towers at sunset

Image: iStock/xijian


WHAT is baseload power anyway?

It is easily explained in terms of electricity demand – demand can be classified as ‘peak’ and ‘average’. Average electricity demand is otherwise known as ‘base’ demand.

While base demand is relatively constant and similar day-to-day, peak demand is the maximum demand, and this may only happen for a very short period of time. For example, on a really hot day when everyone turns their air conditioners on. Peak demand may only happen for a few hours on a few days of the year.

Demand is changing

Electricity demand in Australia is getting more ‘peaky’. On average we are using less electricity per day (as people and businesses get more efficient), but a lot more electricity is being used on just a few particularly hot days (as more people get air conditioners).

In some cities, the peak demand, which only happens for a few hours on a few days of the year, can be double the average demand. This is a real challenge – to avoid blackouts, electricity generating and carrying capacity is required to supply the peak demand, but that capacity is only used a few days of the year.

Managing base and peak demand

Electricity generators are often classified as ‘baseload’ or ‘peakers’.

Traditional, baseload generators have been the steady, on-all-the-time electricity generators that supply the constant on-all-the-time base electricity demand. In Australia ‘baseload’ generators have usually been large coal-fired power stations.

headshot of researcher

Dr Glenn Platt is Research Director; Energy at CSIRO

Generally, baseload generators are fairly slow in changing the amount of electricity they generate, so to match sudden changes in electricity due to peak demand, we use ‘peaking’ generators, which are more flexible and dynamic in how they produce electricity. Such generators can quickly ramp up or down to match changes in demand, and are usually based on hydro or gas generators. However, the electricity that peaking plants (especially gas) produce is more expensive than that from baseload coal plants. The most common solution has been for cheaper coal-powered plants supply baseload, and more expensive gas plants (or hydro) supply the variable peak component of our demand.

A role for renewables

With the growth in intermittent renewable energy sources such as wind and solar, a significant amount of our generation capacity can now quickly ramp up and down as clouds shade solar panels, or the wind gusts up and down, resulting in a large amount of electricity generation in the system, that itself is fluctuating.

While the traditional approach of steady, constant ‘baseload’ generation augmented by flexible, dynamic ‘peaking’ generation is one way of ensuring reliable electricity supply, today there are alternatives to this model. Ultimately, to ensure reliability, we need electricity supply to closely match electricity demand. Electricity systems around the world are showing this can be achieved without ‘baseload’.

These systems have:

  • Flexible generation that can quickly vary its output, like the wind and solar sources mentioned above.
  • ‘Demand management’ techniques that can vary electricity demand to match supply. For example, electricity loads such as hot water or pool pumps can be turned on/off, matching the available supply, and the consumer would never notice any change.
  • Energy storage (for example, batteries or pumped hydro) to fill in any short-term gaps between supply and demand.

These concepts matched with sophisticated load and generation forecasting schemes and careful control, mean that electricity systems can operate reliably with a large amount of renewable energy, without needing baseload generation.

More about reliability

There are significant technical questions about exactly how much intermittent renewable energy a power system can cope with and still be reliable. Theoretically, with careful load and generation control systems mixed with energy storage, a power system could operate on 100 per cent variable renewable energy, and this has been demonstrated on various small grids around the world (such as those on remote islands). However, there are open questions about how such results translate to a large grid with major industrial loads, and what the cost of such an approach would be.

But how do these results translate to a large grid with major industrial loads? And what would the cost of such an approach be?

Australia needs to be certain of exactly what percentage of renewable energy our power system can cope with while staying reliable. Is it 40 per cent? 60 per cent? 100 per cent?

The effects of these options vary dramatically depending on scale. For example, while the state of NSW may be able to cope with 40 per cent renewable energy, a particular remote part of the Hunter Valley may be able to cope with only 20 per cent renewable energy on that segment of grid, due to constraints in the infrastructure installed.

Once upon a time, it was thought that power systems would struggle to integrate 40 per cent variable renewable energy. We now know from practical examples in major grids that isn’t true. But we don’t really know how far this can be pushed, or more accurately, what the trade-offs are between cost, reliability and variable renewable energy penetration. It is likely supply could be reliable with 100 per cent renewable energy in the grid, but this might be much more expensive than (for example) only 90 per cent renewable energy.

While these upper limits could be achieved from a reliability perspective, Australia is currently aiming for around 23 per cent renewable energy so for the time being the debate is purely academic.

Dr Glenn Platt is Research Director; Energy at CSIRO.


  1. Unfortunate that Australia is only aiming for around 23% renewable energy, when there is so much potential for it. We are continuing to use non-renewable and GHG emitting technology despite the evidence of impacts on our climate – still a heads-in-the-sand approach. From the hip pocket perspective, solar panels on our roof has made a big impact on our power bills.

  2. ‘…a particular remote part of the Hunter Valley may be able to cope with only 20 per cent renewable energy on that segment of grid, due to constraints in the infrastructure installed.’ Which is the chicken and which the egg. The infrastructure would have been constructed when coal fired power was king and designed to best suit that. If we move to renewables we may need a completely different model for the infrastructure??

    1. Hi Brian, thank you for your question. This is a response from Dr Glen Platt (Research Director – Energy): “Its certainly true that as our power system changes, the infrastructure will need to change, in many ways. An example here is AEMO’s integrated system plan, which refers to many ways the infrastructure in the energy system will change over coming years.”

  3. Wrong! Baseload power isnt Average power. Its the minimum power demand, usually round 2 or 3 am. The name came about with the early nuclear power plants that could not be turned down easily or quickly, so were used to the supply a constant Baseload power. Coal, hydro and gas provided the ‘load following’ power for demand above the Baseload. The use of Baseload in current discussion is almost always incorrect. People should talk about Dispatchable power. Ie power that is available when needed, which is often when the sun isnt shining and the wind isnt blowing.

    1. Hi Ken Nee, thank you for your comment. This is a response from Dr Glen Platt (Research Director – Energy): “We’re in furious agreement! What we need is dispatchable, and flexible (in that, as well as turning on to generate, such sources can also quickly turn off) power generation.”

  4. Thanks for sharing this useful information here.
    Good to know about this.
    Team Nama

  5. “Theoretically, with careful load and generation control systems mixed with energy storage, a power system could operate on 100 per cent variable renewable energy, and this has been demonstrated on various small grids around the world (such as those on remote islands)“

    Can the writer identify these remote islands? I know of none.
    El Hierro in the Canary Islands have tried and failed to go 100%.

    1. Hi Peter,
      Thank you for your question. This is the response from Dr Glenn Platt, Research Director of Energy at CSIRO.
      “Kosiak Island, Alaska, Tokelau, New Zealand, Samsoe Denmark are some of the islands that have been reported as operating close to 100% renewable energy, and many more have plans in place to realise this goal.
      Regarding the second question, it’s true the grid needs to evolve to cope with high penetrations of renewable energy. The AEMO Integrated System Plan details the changes planned in Australia for such evolution.”

  6. Is it a case of the chicken or the egg for ‘baseload’ power? For instance it was/ is common practice to encourage off-peak use through lower prices (eg HWS). Because of the limitations of a coal-fired system and the difficulty with meeting a fluctuating demand, various techniques have been used to even out the demand..

  7. As renewable costs diminish, another control possibility appears. If renewable capacity rises to match or exceed predictable peak demand, renewable units can be throttled to deliver just 100% of demand. That suggests a change in the operation of large demand units, such as aluminium smelters, cement kilns or hydrogen electrolysers so the available power excess can be cheaply despatched through a market system. I’m sure this is being contemplated in industrial planning today.

  8. Glenn: You and I have never met: however: could I offer to buy you coffee or lunch one day soon to discuss: Renewable Energy: We in Australia are doing the opposite to what Electrical companies are doing in the northern hemisphere: they do not even discuss 100% renewables: they talk about a new generating ‘MIX’: they do not like large grids: they do like to transmit energy over long distances: they will not discuss pumped hydro systems ‘too expensive’ once ‘off peak power’ is no longer available: no ‘off peak power’ for hot water systems: they are establishing micro grids: heavy load new installations are developed on a MICRO GRID: you know and I know it is virtually impossible to control a SMART GRID: you would understand: SMART GRID; SMART CITY: SMART TECHNOLOGY: etc.
    Yes I am an Electrical Engineer specialising in POWER SYSTEMS: I have a Mechanical Engineering Certificate: A Qualified Overhead Lineman’s Certificate : an ‘Honours’ Grade Electrical Trades Course Certificate and over 60 electrical experience: I believe you and could have an interesting discussion.
    I will ring you: Mr No Body.

  9. The real miracle of clean energy is something that very few wish to talk about: renewable power is “cheaper”, but, amazingly, wherever it is used, power prices go through the roof.

    Perhaps this has something to do with the pressing need to redistribute wealth, taking it away from those who have worked for it and giving it to those who will squander it (global socialism is a wonderful thing).

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