The Federal Office for Building and Regional Planning

Publication Report on the Abandonment of Electric Off-Peak Storage Heating

BBSR-Online-Publikation 20/09, Eds.: BMVBS/BBSR, August 2009

Series: BBSR-Online-Publikation Published: 2009

Editing:
Bremer Energie Institut, Bremen (contractor)
Karin Jahn, Wolfgang Schulz
in co-operation with
Institute for future energy systems (IZES), Saarbrücken
Günther Frey
Fachhochschule für Wirtschaft, Berlin
Prof. Dr. Stefan Klinski

Federal Institute for Research on Building, Urban Affairs and Spatial Development, Bonn
Horst-P. Schettler-Köhler (project leader) horst.schettler@bbr.bund.de

Executive Summary

Background

On its Meseberg retreat in 2007, the German Cabinet has decided among other points in the long run to completely replace electric off-peak storage heating for more environmentally friendly sources of heat supply. The retrofit obligation will be attached to the Energy Savings Regulation (EnEV 2009) which is approaching its renewed amendment process.

In 2007, IZES gGmbH and Bremer Energie Institut prepared a study for the Federal Environment Ministry which already identified off-peak storage heating systems as consuming more primary energy to reach given room temperatures in comparison to common alternatives and hence correspondingly contribute to an increase in CO2 emissions. From the environmental point of view, the study recommended the replacement of these systems. In doing so a consideration should have been given to the demand that the energy saving act, which is superior to EnEV, contains the criterion of economic feasibility for all proposed energy saving requirements.

The previous study has shown that the economic feasibility of pump-run hot-water heating system retrofitting according to legal prescriptions can present a problem due to high expenses connected with such retrofits. From this perspective, attaching the retrofitting obligation to EnEV leaves from the outset onwards little space for the proper execution of retrofits as demanded by regulatory measures. There will be many instances where the retrofitting will be dependent from subsidies.

The present study aims, based on the results of preceding study, to understand the economic feasibility limits for the retrofitting of the off-peak storage heating and to determine the possible areas where exceptions to the rules will be necessary in its application. The results are expected to set the foundations for a proposal of a multiple level support scheme directive for retrofitting obligations.

Method

In order to identify the economic feasibility limits and the areas where the exceptions may be necessary, the study has drawn upon the statistical payback periods. An action is considered to be economically feasible if the payback period is shorter than the economic life-time of the new heating system.

Three model buildings, which had also been used in the previous study, were used as an initial point for the economic analysis. These model buildings were originally selected on the basis of statistical data on electrically heated total stock in Germany. The selected buildings are a single family row house (RH), single-family detached house (EFH), and a six-family house (6FH). It was shown that these alternatives cover a spectrum of typical applications for electric off-peak storage heating in residential buildings.

In addition to seven heating alternatives already considered in the preceding study for the single family detached house (EFH), the study introduced an air-water-heat pump into the analysis.

Apart from the type of the building, there are other factors which influence the economic feasibility of off-peak storage heating retrofitting. Factors such as the grade of building’s insulation, the price of off-peak storage heating electricity, residual value of current off-peak storage heating system, as well as the number of applied heating systems. The ef-fect of these factors has been analyzed on the basis of the calculus of variations. Furthermore, an additional set of exceptional cases have been analyzed where the retrofit obligation for the off-peak storage heating system might prove to be especially problematic as e.g. limited space available for new heating systems or a case of a multi-family house possessing flats with different heating systems.

Results

The main results of the study:

  • the retrofitting of the off-peak storage heating system in all three analyzed reference buildings is economically feasible if there is a natural gas supply available, or alternatively when there is an option of connecting to a cogeneration facility through a local district heating system. A row house, comparable to small single family house, constitutes here the boarder of economic feasibility.
  • electrically oriented heating options of a split-system air-conditioning unit and an air-water-heat pump are under no circumstances an economically feasible alternative.
  • oil heating and pellet heating with or without solar heating systems are economically feasible alternatives for the apartment building with at least 5 apartments.

The analysis of the intervening parameters has shown that in the case of the single family detached house (EFH) and in case of the row house the decreasing heat demand may influence the economic feasibility of the retrofitting. Additionally, early abandonment of the off-peak storage heating system before the end of its economic life-time also negatively influences the economic feasibility of the retrofitting. The only exception showing recognizable tolerance against the economic life-time is the case of natural gas heating; especially for the case of an apartment building.

In contrast, an increase in the electricity price for off-peak storage heating could significantly improve the economic feasibility of the retrofitting. An increase from the original 9 to 12 ct/kWh (without tax) could make, for example, in the case of EFH pellet heating an economically feasible retrofitting alternative in addition to natural gas heating and oil heat-ing. However, even under these circumstances, the option of natural gas is the only economically possible alternative for RH.

With respect to the analyzed exceptional cases it was found that only off-peak heating systems under low loads situated in big buildings, which correspond to the five-family house, present an economically feasible alternative for retrofitting. However, this is the case only under the condition that they are replaced by a natural gas heating system or a district heating. Limited space availability for the new heating system, as well as the absence of a flue present no significant obstacles for any of the reference buildings when there is a source of natural gas or access to a local/district heat available. However, if these are unavailable, the absence of flue makes the retrofit in smaller buildings (RH and EFH) to become an economic problem; and also in the case of smaller apartment buildings, where the costs connected with flue, which is necessary for the retrofit to oil or pellet heating, are at the edge of tolerability. In apartment buildings where flats are equipped by different types of heating systems, the retrofitting of apartments using off-peak storage heating to a structure using a central heating system did not prove to be economically feasible.

Opposite to this, a replacement of the floor heating using resistance wires was found to be even more profitable than the retrofit of the off-peak storage heating units. Also the retrofitting of the central off-peak storage heating system, where the distribution of heat through the pump-driven warm water system is already present, with the exception of electricity driven versions, was found to be profitable for all evaluated alternative systems. However, for the case of RH, the retrofit from off-peak storage heating to oil or pellet heating system admittedly stands at the boarder of economic feasibility.


The abstract is part of the German publication "Gutachten zur Außerbetriebnahme von elektrischen Nachtspeicherheizungen", BBSR-Online-Publikation 20/09, Hrsg.: BMVBS/BBSR, August 2009, Bonn
ISSN 1868-0097, urn:nbn:de:0093-ON2009R2299
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