Change in heating costs for different renovation alternatives of a million-housing program building

In 2014 the network for energy efficient multi-residential buildings, BeBo, finished a project called “Ett hus, fem möjligheter” (“One building, five opportunities”). The purpose was to provide insight into and a comparison of five different renovation alternatives for an existing building from the million-housing program, resulting in a decrease in energy use by at least half. Since the completion of this project the district heating tariffs have undergone deeper differentiation and added complexity, with several price components that make up the total DH (district heating) price, such as power price, energy price and return temperature discount or fee. Meanwhile, average electricity prices in Sweden have increased. The impacts of these price developments on the energy cost savings of the five alternatives in “Ett hus, fem möjligheter” have not been investigated. Due to this, the consultant company WSP, which is tasked with coordinating BeBo, requested an investigation on what change there has been in heating costs for the renovation alternatives from “Ett hus, fem möjligheter” between 2014 and 2019 in the city of Stockholm, with focus on Stockholm and Solna municipality. Energy demand for the building and its alternatives was simulated and entered into an energy cost calculation tool called PRISMO developed by BeBo in 2017, together with energy price structures for Stockholm municipality (from Stockholm Exergi for DH and from Ellevio for electricity) and Solna municipality (from Norrenergi for DH and from Vattenfall Eldistribution AB for electricity). The results showed a change in energy cost for all alternatives in all scenarios. In Stockholm municipality, both district heating and electricity cost has increased for all alternatives. DH cost has increased by between 15% and 18% for the base building and all alternatives using only DH (alternatives 1 and 2). In alternatives with combined DH and electricity the DH cost has increased by about 24% where DH is used for domestic hot water and peak heat load, and by slightly more than 30% where DH is used for peak heat load only. Alternative 5.2, with DH for peak load and where DH power demand is low due to higher heat pump power, sees the highest increase in DH cost, being 49%. This is despite lowered energy cost, primarily due to significant increase in the power cost and lowered return temperature bonus. Electricity cost has increased by about 30%. The buildings with a higher share of power cost compared to energy cost have seen a larger increase between the years, and high electricity demand has also contributed to a larger cost increase. In Solna municipality the DH price structures did not change considerably between 2014 and 2019 and as such the DH costs see only small changes. Most of this change in DH cost is due to a change in power price coming to favor buildings with power demand above 96 kW, with small contribution from a minor energy price reduction. Return temperature malus did not change between 2014 and 2019. The DH cost has decreased for all applicable alternatives by at most 2%, except for alternatives 1 and 5.2, where it has increased by 0.3% and remained the same, respectively, due to higher relative power cost for their lower power levels. Similarly to in Stockholm municipality, the electricity costs have increased significantly, by about 35%. Alternatives partially or fully heated by electricity have all shown an increase, which is lesser the higher the extent of DH use is. Accordingly, the largest increase in energy cost is found for the fully electrified alternative 5.1 . Energy cost changes obtained in this study were compared with changes in energy cost reported by the Nils Holgersson Gruppen, a reporting group created by various housing companies and associations in the industry. The comparisons show that energy cost changes are aligned for both DH and electricity in Solna municipality and for electricity in Stockholm municipality. However, the cost change for DH in Stockholm municipality in this study is about +15-18% for DH-only alternatives, whereas this change is reported as -2% (between 2014 and 2018) by Nils Holgersson Gruppen for their DH-only reference building. Implementing Nils Holgersson’s reference building energy demand data in PRISMO together with DH price structures of 2014 and 2019 for the same municipality shows that there is an increase in DH cost by 8.2% over this time period, excluding return temperature discounts or fees, as return temperature is not considered in the Nils Holgersson Report