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What to do with the electric instant shower?

image credit: Electric instant shower at my own home
Rafael Herzberg's picture
Consultant energy affairs, Self employed

Rafael Herzberg- is an independent energy consultant, self-employed (since 2018) based in São Paulo, Brazil* Focus on C level, VPs and upper managers associated to energy related info, analysis...

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  • Aug 29, 2020

What to do with the electric instant shower?

The installed power in electric showers in Brazil is over 100 GW.

The country's nominal capacity of electricity generation is 160 GW and the maximum demand is 80 GW.

The electric shower is an important responsible for the peak of national demand.

I have a suggestion - without capital investment - to significantly reduce the peak demand. It is an opportunity for the electric utility companies and their customers.

Get in touch to know the strategy that could turn around the situation of the electric sector in Brazil. It is a demand response (DR) type proposal! 

Joao Batista Gomes's picture
Joao Batista Gomes on Sep 5, 2020


This is what we did in the 90s here in Brazil, about the electric shower.



Rafael Herzberg's picture
Rafael Herzberg on Sep 8, 2020

Hi João Batista,

Thanks ! After reading your paper (link indicated in your comment) These are my questions:

1) What kind of strategy was deployed by CEMIG and partners in this initiative to stimulate the residental energy users to go for the proposed time of use rates?

2) When peak demand was approaching in a given day, did CEMIG was able to shut down the electric showers? I mean like a US type demand response program using the client's wi-fi to "take action" ort was it basically a signal sent tothe customer, not to use the electric instant shower?

3) According to my experience with load control (to reduce peak recorded demand and accordingly the billed demand) for industrial/commercial and institutional energy users in the 500 kW - 30MW contracted demand range, it is very difficult to just offer time of use rates as a way to stimulate them to reduce their on-peak recorded demands. Experiece with DR programs in the US (among other countries) indicate that when a hefty bonus is there on the table, then there is motivation to reduce demand. In this line of thought did CEMIG offered a generous bonus?

4) What results came up with respect to the indicated in your paper actions? What was its financial value? Was CEMIG happy with the results? And were the clients happy also? Is the program still active? Was it replicated?

Again thanks for your comments! And I am looking forward to hearing from you again!

Joao Batista Gomes's picture
Joao Batista Gomes on Sep 11, 2020

You asked a lot of questions, here are some answer.

When we speak of DSM, we are targeting the residential consumers, for industrial and commercial consumers due to the nature of their businesses better tools are developed for this.

With the development of Smart Meters is possible to add intelligence to the network and individual features of each residential consumer.
The main parameters for managing the demand side are not the hourly consumption of energy, but the maximum demand.

Size of residential, class of consumption and home infrastructure, will serve to define the maximum demand in peak hours of each consumer, so this will be a dynamic process

When we talk about Smart Meters, does not make sense if they do not have at least the following features:
1-Different fields of tariff;
2-Relay cutting and automatic restart;
4-Measurement of energy in KWh;
5-Measurement of maximum demand in KW;

At peak times the meters are programmed to limit the consumption of certain levels, as they have clock and measure the energy consumed that is the easy part.

The limit of consumption of each consumer is given by its maximum demand, ie, the consumer might use the lights, sound, thermostat, TV and refrigerator, but can not use the washing machine and dryer, electric showers and microwave and heating water bath at peak time and other tools for energy-intensive electric.

The meter is programmed  at peak times, if the consumer exceed the limit of consumption established with Utility, relay cut open and close after 30 seconds, measure the consumer again, and if consumption is within the level established remained closed, if not, opened again and so on.

This meter can be programmed remotely to change the peak time, change of level of consumption and on weekends and holidays consumption can be totally free.


We need stories for different market segments, the Smart Grid Projects has as one of its main features the flexibility to meet the energy needs for all segments of the market and should always have something for everyone.

The benefits of Smart Grid Projects are difficult to quantify, because the answer depends on how is the activation functions of the technologies involved.

Without a careful program, and also without elaborate tools for measuring success or failure, we risk leaving many benefit overlooked on the table.

If we understand that the “Wires” that carry the energy to the consumer units can be considered as Ducts. When you “expand or narrow” this Duct, you can vary and control the energy that each consumer unit can consume.

In a way the Utilities have always done this using the load carrying capacity of Circuit Breakers installed in the consumer units, but never had the ability to increase or decrease the flow of energy.

The Circuit Breakers are mounted together with the Relays in the same case, and connected in series. The inputs of Circuit Breakers are interconnected, as well as its outputs. Each set of Breakers and Relays has a “differentiated load capacity”, and then each set may control the Maximum Demand (KW) of each consumer unit.

Each consumer unit can only have one set of Circuit Breaker/Relay in "ON" mode, while the others set, remains in "OFF" mode. For there to be the exchange of a set on the other, first you turn to "ON" mode the set you want, then you turn to "OFF" mode the other set. So in this way there is no discontinuity in the supply of energy to the consumer unit.

In the project where I tested this new approach, a set of Circuit Breaker/Relay had a capacity of 20 AMP, and the other set had a capacity of 40 AMP. But this specification, and quantity of sets, can be changed according to the needs of each project. Most Smart Meters already has the function of "connect and disconnect" remotely the consumer, this feature is also used for the exchange of sets of Circuit Breaker/Relay

The management and control over the flow of energy for each consumer unit is controlled by a Smart Meter, which remotely receiving the daily schedule.

Of course when this solution is applied, the consumer must be in accordance, and in many cases get a discount on your monthly energy bill.


Rafael Herzberg's picture
Rafael Herzberg on Sep 14, 2020

Hi João Batista,

From what you wrote (above) I am led to believe that it is about expectations, not (so far) about results of a program that was actually  launched and results were verified.

Joao Batista Gomes's picture
Joao Batista Gomes on Sep 14, 2020

Honestly, I do not know where did you get these conclusions.
This project was developed for CEMIG, which had a problem of excess energy demand during peak hours, in the Jequitinhonha valley and in the north of the state of Minas Gerais.
At the same time, Cemig had a project to build a Hydroelectric Plant in the region that would take another ten years.
The solution found was the implementation of a DSM project, which would shift the use of the electric shower from peak hours.
There were 100,000 consumers in this project and all benefits are in the public domain, you can search for this on the Web, Eletrobras and CEMIG.
Then this project was expanded to the south of the state of Minas Gerais. Where in the winter with the coffee harvest, you had an increased demand for energy that matched the peak hours.
This same project was implemented in the states of Rio de Janeiro, Espirito Santo, São Paulo, Mato Grosso do Sul, Goias and Bahia.




Rafael Herzberg's picture
Rafael Herzberg on Sep 15, 2020

I am sorry I have misundertood your comments.

Could you tell us then what were the actual results in terms of demand reductions in each area where this projects was deployed?

Joao Batista Gomes's picture
Joao Batista Gomes on Sep 15, 2020


The demand reduction varied from 200 watts to 500 Watts, for each point/consumer that participated in the project.
This variation is due to the load profile of each consumer unit.



Rafael Herzberg's picture
Rafael Herzberg on Sep 16, 2020

Hi João,

Is there an offical report about this project (associated with electric instant showers)? If so could you indicate the designated link? 

Thanks in advance!

Rafael Herzberg's picture
Rafael Herzberg on Sep 16, 2020

Thanks João,

These two papers primarily describe wha was done. And sure it is very interesting. 

Is there info about aggregated results in a systemic fashion?  I mean specifically:

1) How many households were involved in each utility's coimpany service territorry?

2) What was the difference (measured in GWs) - in terms of demand (integrated by 15-min-intervals) before and after the experiment?

3) How does this difference in GWs refer to the marginal cost of the expansion of the power supply chain in each region where the experiment took place?

4) Was the granted bonus (to the home owners) fair when compared to the savings (item 3 above)? In this line of thought, was the local utility company happy with the results? 

5) With the actual results what was decided with respect to extending this solution to other areas?

6) This demand-reponse type program was extended to other segments of the market (C/I for instance)? 

Thanks in advance for your comments regarding each question!

Joao Batista Gomes's picture
Joao Batista Gomes on Sep 16, 2020

You must keep in mind that this project was done 20 years ago, with the technologies and knowledge present at that time.
This project was carried out especially for CEMIG, which wanted to postpone investments in the area of ​​Transmission and Distribution in the Jequitinhonha Valley region.
The growth in residential energy consumption in this region was practically nil.
CEMIG had a hydroelectric plant under construction in the region that would take about 7 years to start operating.
At peak times, the electric shower caused a lot of instability on the grid.
I was the technical manager for this project, and I developed this project taking into account this situation at CEMIG.
All consumers participating in this project were monophasic, and had a 20 percent discount on their monthly energy bill. For low-income consumers, this discount was important.
The other Utilities knew about the problem of electric showers on the grid, and just followed the line adopted by CEMIG without any pre-assessment.
Eletrobras and CEMIG have more technical information regarding this project, but I have no authorization to make this information available.
Using this same architecture and topology I developed an AMR/AMI project for CEMIG in the cities of Contagem, Juiz de Fora and Alfenas.
This project was to get to know the load profile of consumers in these cities.
At that time Brazil had around 150 thermoelectrics, today there are more than 2000.
Carbon emissions and climate changes at that time, did not have the current visibility.
So energy efficiency was left out for the construction of more polluting plants, and it was a mistake. Today this project is still very up to date and can be put to work with only a few updates.



Rafael Herzberg's picture
Rafael Herzberg on Sep 18, 2020


It occurred to me that me might team up to craft a demand response type program to selected local electric utility companies in Brazil. You seem to have experience dealing with them and I have in mind a program that could produce great results,

Here goes my contact info: and +55.11.99986 5563 (mobile/whatsApp)

Rafael Herzberg's picture
Thank Rafael for the Post!
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