Savings

Energy use

The form that Boverket has adopted for energy declarations specifies the different types of energy usage in order to get at the part that has a bearing on the energy performance of the building. The energy we refer to here is the purchased energy. Data on measured values is used in the first place and if this is not available, the values that have been allocated by the property owner and/or the expert are used instead. The values specified are not corrected for a normal year. With respect to small houses, the main concern is that the expert should correct the energy use for the effects that can be attributed to a known but "abnormal" behaviour of usage.

When weather data is considered, a value is calculated that is corrected for a normal year for energy use. This value per m2 tempered area (Atemp) is called the energy performance of a building.

In order to gain an understanding of how reliable this value is, it is compared with two different reference values. The first reference value is Boverket's requirements for new construction for this type of building. The second reference value is a value with associated interval that is derived from the material produced by Boverket. It is based on the corrections for the activity, heat source, area, age, type of construction, and for premises and ventilation flow and cooling.

The above data provides support for assessing energy use prior to taking any measures, and the potential for energy savings. For the latter, the expert will have access to general data that shows which saving can be attributed to which measure. It may also be appropriate to produce energy balance calculations using established software.

Energy costs and trends

The financial value of energy savings depends on present energy costs and their future development.  A measure often only affects one type of energy. If several types of energy are involved, you need to consider whether these will be subject to differing cost development patterns. Note that the costs to be included in the calculations are those that are influenced by a particular measure. This normally means variable costs rather than fixed.  Occasionally semi-fixed costs are also affected; irregular changes to tariffs when, for example, a certain output level is passed. If these conditions are known and are expected to remain stable, they should be included in the calculations.

Changes to other operations and maintenance costs

A frequently overlooked fact is that the installation of energy saving equipment may result in a changed need for operation and maintenance investment. Intermittent maintenance investment (e.g.10-year measures) may be added when they are expected to arise, while other costs of this type are converted to average annual values that are obtained from company or industry statistics.