*3.6. Summary*

In DH and wood heated cases, the energy retrofit decreased the use of DH and boiler, but increased electricity consumption due to the air-source heat pumps that were included in all optimal solutions. Solar power did not influence peak power demand. In buildings with a ground-source heat pump or direct electric heating, the electricity consumption went down for both the D and B level retrofits. From the national and regional energy system point of view, it is useful to know the range of power demand of the buildings before and after the retrofits. These results are shown in Table 6. Shown in the table are the maximum and minimum (single hour) power demand for the month of January (high demand and emissions) and July (low demand and emissions). Also shown is the sustained peak/bottom power demand, which is the average power of the 5% of hours in the month (37 h) with the highest/lowest demand. Finally, it shows the median power demand of the whole month. Negative values represent exports of excess solar electricity back into the grid.

**Table 6.** Electric power demand for all reference and retrofit cases. Results are shown for January (a high emission month) and July (a low emission month). The reported values are the absolute maximum and minimum power demand, the monthly top/bottom 5% of power demand (average power of 37 highest/lowest demand hours) and the median power demand. Negative values represent exports of excel solar energy to the grid.



**Table 6.** *Cont.*

In January, retrofitting district heated or wood heated buildings increased median electric power demand by 33 to 108% or 1.3 to 3.7 <sup>W</sup>/m2. The increase was due to the air-source heat pumps included in all the retrofitted cases. Switching from a wood boiler to GSHP increased median power demand by 95 to 272%. This was 5.1 to 8.5 W/m2 for the D level retrofit and 3.7 to 5.2 <sup>W</sup>/m<sup>2</sup> for the B level retrofit. The increase was smaller for the new buildings SH3 and SH4. The maximum power demand increase in the switch from wood to GSHP was much larger. Level D retrofit increased maximum power by 23 to 32 <sup>W</sup>/m<sup>2</sup> and level B retrofit increased it by 9 to 14 <sup>W</sup>/m2. In July the difference between peak and median demand is smaller. The largest effect is the solar electricity production, which is seen as highly negative minimum and sustained bottom power demand.

In January, the median electricity demand in the electrically heated buildings was reduced by as much as 22 <sup>W</sup>/m2, while the maximum power demand was reduced by up to 30 <sup>W</sup>/m2**.** In buildings with GSHP, retrofit B reduced maximum power demand by 9 to 35 <sup>W</sup>/m<sup>2</sup> (36 to 68%), depending on the building age. Median power demand was reduced by only 2 to 7 <sup>W</sup>/m2. The large difference between these changes was caused by electric backup heating, which is only used during peak demand hours. In the GSHP B cases, the heat pump capacity was large enough to meet all loads without backup heating.

The results for the building stock scenarios (as described in Section 3.5.) are shown at the end of Table 6. In the detached house building stock, electrically heated buildings (with heat pumps or direct electricity) make up a significant portion of the houses, especially in the retrofit scenarios (as described in Section 3.5). The maximum combined specific power of the building stock was below that of GSHP buildings only, but above that of wood and DH heated buildings. The maximum power in the Retrofit D scenario was increased vs. the Original case, but remained on the original level in the Retrofit B scenario. The retrofits in electrically heated buildings reduced the power demand enough to compensate for the higher penetration of heat pumps. The median electrical power demand in January was 13.8 <sup>W</sup>/m<sup>2</sup> for the Original and Retrofit D scenarios and was reduced to 11.6 <sup>W</sup>/m<sup>2</sup> in the Retrofit B scenario. In July, the power demand never rose above 7 <sup>W</sup>/m2.
