The aim of this master thesis project is to make an energy survey for a group

of apartments and suggestions to change the heating system from electricity to a more

efficient one. There are in total 73 flats in 21 buildings. All flats are separated in several

houses from two to five flats in one building. There are two different kinds of flats. One

with three rooms in one floor, in the following referred to as ‘flat A’ and the other one

with four rooms in two floors, in the following referred to as ‘flat B’. [1]

In the area there are also two buildings for the commonalty. In these buildings there are a

shelter and several common rooms like a storage and a laundry. In our work these two

buildings are not included because they are used by everyone inside the community and

we could not obtain exact values for the used electricity and the water consumption. So

our work is specialised only on the residential houses.

The first part of this thesis contains the energy balance for the different kinds of flats to

see how much energy they consume for heating and hot tap water. To get theses values

we have to analyse the total energy flow into one flat and compare it with the energy

which is used because of transmission losses, ventilation losses, hot tap water, electricity

for the household and natural ventilation and infiltration.

The total energy consumption for flat A is about 19000 kWh per year and in flat B about

23200 kWh per year. But the electricity which is used and has to be bought is about

15600 kWh per year in flat A flat and 17600 kWh in flat B. The rest of the energy is from

so called free heat caused by solar radiation and internal heat generation. [1]

These numbers for the electricity need in one year create annual costs of about

20000 SEK in flat A and 22500 SEK in flat B. To reduce these costs it is necessary to

know where this energy goes and for what it is used.

The important parts of the energy balance for this thesis are the transmission losses, the

losses caused by natural ventilation and infiltration and the used energy for hot tap water.

The losses caused by mechanical ventilation have also a significant value, but they would

only affect the new heating system if the ventilation system would be connected to the

new system. And the electricity used in the household for electrical devices can only be

changed by the consumer himself. The part which is affecting the energy costs for the

transmission and natural ventilation losses and the hot tap water sums up to 9240 kWh per

year in flat A and flat B. This causes costs of about 10000 SEK per year.

To reduce these costs it is necessary to change the actual heating system. In the following

we analyse the saving potentials with a change to an air-water heat pump or with a

connection to the local district heating network.

The costs which can be saved with the installation of a heat pump sum up to about

7000 SEK per year. The installation costs are about 100000 SEK to 125000 SEK

depending on the different proposed models. If you consider that the existing electrical

boiler has to be changed anyway in the next years the investment costs for the

combination with a heat pump decreases. The payback time is then between 9½ and

13½ years. With assumed increasing electricity prices of 5 % each year the payback time

decreases to 8½ to 11 years.

With a connection of each flat to the local district heating network the energy costs for

heating and hot tap water decreases to 3200 SEK per year. Although the price per kWh for

district heating is much lower than for electricity the costs are not decreasing a lot

because of a high annual fixed fee of 7100 SEK. The saved money per year sums up to

300 SEK and 1000 SEK depending on the electricity contract. The payback time for this

alternative is between 50 and up to 160 years.

An alternative to the exchange of the heating and hot water system is to change the actual

heat exchanger of the ventilation system. With this measure the energy consumption can

be reduced with less investment costs. The investment costs for a new heat exchanger are

about 35000 SEK, including a new exhaust hood from the kitchen outwards to reduce the

contamination of the filters in the heat exchanger. [1]

The payback time ranges from 13 years in flat A to 21 years in flat B.