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[PP11] Heating and cooling degree days
State

Key message
Neutral

Comparison of periods 1961–1990 and 1991–2020 on the chosen representative stations around Slovenia shows decrease of heating degree days by around 10 % and multiple increase of cooling degree days. With projected continuous temperature raise until the end of 21st century, those trends are expected to continue. Thus, in Slovenia, energy demand for cooling will increase in the warmer period of the year, while the energy demand for heating will decrease in colder period of the year. Same trend is projected for Europe in general.

Charts

Figure PP11-1: Annual heating degree days at selected weather stations in Slovenia, 1950–2024
Sources:

Slovenian Environment Agency, 2025 (12/08/2025)

Show data
Kredarica[Kday] Ratece[Kday] Murska Sobota[Kday] Novo mesto[Kday] Ljubljana[Kday] Bilje[Kday]
1950
1951 7824 4637 3180 3137 3054 2426
1952 7873 4501 3298 3166 3124 2649
1953 8010 4765 3639 3588 3361 2830
1954 8040 4691 3793 3654 3402 2800
1955 8063 4747 3634 3476 3270 2723
1956 8480 4931 3783 3686 3500 2950
1957 7781 4680 3656 3556 3278 2803
1958 7891 4775 3527 3344 3294 2614
1959 7656 4350 3111 3051 2884 2468
1960 7963 4590 3457 3407 3173 2621
1961 7759 4434 2962 2924 2730 2280
1962 8012 4867 3544 3478 3250 2753
1963 8354 5200 4010 3838 3662 2989
1964 7705 4609 3634 3473 3232 2647
1965 8202 4967 3530 3573 3361 2848
1966 7961 4644 3286 3152 3069 2704
1967 8121 4604 3157 3200 3046 2591
1968 7791 4460 3262 3082 2988 2537
1969 8137 4842 3592 3445 3350 2750
1970 8299 5013 3644 3565 3376 2844
1971 8016 4788 3408 3294 3171 2743
1972 7757 4682 3522 3463 3269 2733
1973 8175 4918 3764 3666 3503 2914
1974 7902 4554 3422 3288 3092 2710
1975 8033 4681 3275 3235 3091 2793
1976 7918 4565 3620 3516 3381 2823
1977 8024 4634 3179 3083 2873 2374
1978 8142 4945 3551 3526 3316 2814
1979 8034 5076 3710 3565 3450 2912
1980 8293 4975 3675 3517 3336 2842
1981 7942 4921 3586 3459 3374 2944
1982 8092 4798 3510 3440 3283 2885
1983 7589 4237 2992 2879 2826 2467
1984 8059 4907 3701 3522 3433 2879
1985 8084 4828 3689 3553 3337 2775
1986 7773 4616 3507 3441 3286 2660
1987 7997 5057 3853 3638 3477 2862
1988 7617 4330 3145 3004 2875 2416
1989 7414 4504 3278 3141 3008 2616
1990 7418 4417 3092 2990 2881 2662
1991 8048 4986 3623 3382 3294 2621
1992 7671 4422 3238 3164 3140 2741
1993 7305 4362 3243 3080 3009 2601
1994 7746 4464 3010 2963 2817 2353
1995 7559 4355 3176 3141 3002 2548
1996 7833 4673 3623 3408 3171 2625
1997 7826 4540 3508 3369 3092 2503
1998 7563 4276 3205 3047 2892 2490
1999 7729 4590 3305 3242 3083 2631
2000 7537 4172 3116 3015 2938 2548
2001 7476 4003 2648 2480 2471 2059
2002 7437 4353 3170 3050 2893 2450
2003 7651 4206 3390 3216 2993 2375
2004 7685 4736 3334 3223 3117 2619
2005 7738 4570 3310 3197 3056 2563
2006 7882 4778 3456 3316 3237 2646
2007 6897 3773 2565 2253 2148 1909
2008 7569 4410 3237 3157 3044 2558
2009 7675 4427 2955 2946 2855 2286
2010 7649 4325 3117 3023 3005 2504
2011 7555 4264 3152 3134 2911 2376
2012 7307 4180 3185 3081 2960 2537
2013 7429 4455 3105 3075 2896 2428
2014 7065 4009 2587 2496 2304 1774
2015 7383 3806 2682 2649 2553 2063
2016 7011 4146 2889 2801 2766 2258
2017 7244 4104 3172 2993 2842 2337
2018 7376 4255 2929 2806 2735 2374
2019 7220 4099 2921 2815 2582 2179
2020 6987 3950 2706 2496 2361 1979
2021 7392 4424 3107 2913 2897 2422
2022 7203 4214 3081 3001 2884 2501
2023 7131 4028 2870 2614 2438 2055
2024 6662 3642 2481 2274 2298 2061
Figure PP11-2: Annual cooling degree days at selected weather stations in Slovenia in the period 1950–2024
Sources:

Slovenian Environment Agency, 2025 (12/08/2025)

Show data
Kredarica[Kday] Ratece[Kday] Murska Sobota[Kday] Novo mesto[Kday] Ljubljana[Kday] Bilje[Kday]
1950 0 6 75 95 135 245
1951 0 0 32 31 64 110
1952 0 8 93 83 128 198
1953 0 0 24 25 37 107
1954 0 0 22 17 29 69
1955 0 0 11 14 21 62
1956 0 0 14 20 31 60
1957 0 3 57 70 85 119
1958 0 2 46 50 70 93
1959 0 0 12 19 36 96
1960 0 0 16 8 20 19
1961 0 0 36 34 52 82
1962 0 0 22 27 53 144
1963 0 0 62 58 77 82
1964 0 0 11 17 42 78
1965 0 0 24 29 50 52
1966 0 0 12 18 29 54
1967 0 0 50 49 77 119
1968 0 5 38 39 57 69
1969 0 0 19 20 48 64
1970 0 0 31 33 77 85
1971 0 2 34 35 70 100
1972 0 0 27 33 42 87
1973 0 0 21 24 32 90
1974 0 0 46 45 66 74
1975 0 0 6 10 20 51
1976 0 1 14 28 36 49
1977 0 0 16 23 26 31
1978 0 0 3 9 11 30
1979 0 0 21 27 37 83
1980 0 0 13 25 40 53
1981 0 0 36 46 46 67
1982 0 0 17 36 63 130
1983 0 10 51 57 84 91
1984 0 3 13 27 29 33
1985 0 0 27 40 70 93
1986 0 1 32 41 69 125
1987 0 0 44 49 66 124
1988 0 0 60 74 114 135
1989 0 0 23 21 39 82
1990 0 0 22 41 57 89
1991 0 1 46 62 87 131
1992 0 5 123 89 123 136
1993 0 1 70 101 102 131
1994 0 6 88 116 145 224
1995 0 2 32 50 83 141
1996 0 0 24 32 48 69
1997 0 0 17 15 35 80
1998 0 4 76 103 154 197
1999 0 0 52 60 80 121
2000 0 1 123 134 125 125
2001 0 1 83 113 144 166
2002 0 10 71 69 93 131
2003 0 10 221 234 264 369
2004 0 2 38 56 82 126
2005 0 4 51 71 85 133
2006 0 16 102 133 166 202
2007 0 5 132 114 150 152
2008 0 3 103 93 139 160
2009 0 4 58 96 140 191
2010 0 14 96 119 141 147
2011 0 5 83 120 151 203
2012 0 11 151 177 221 299
2013 0 30 161 157 211 240
2014 0 2 60 58 76 79
2015 0 28 172 186 229 272
2016 0 4 74 92 135 217
2017 0 12 147 202 217 233
2018 0 13 113 96 177 228
2019 0 27 145 168 212 305
2020 0 5 66 99 121 172
2021 0 9 149 176 208 237
2022 0 12 132 175 279 401
2023 0 12 115 140 171 244
2024 0 18 229 237 255 350
Figure PP11-3: Timeline of change in average annual heating degree days in Slovenia over the 21st century
Sources:

Slovenian Environment Agency, 2020 (20/04/2021)

Note:

The timeline of change in average annual heating degree days in Slovenia over the 21st century for three scenarios relative to the reference period 1981-2010. Bold coloured curves show smoothed model median and lighter colours show model.

Figure PP11-4: Timeline of change in average annual heating degree days in Slovenia over the 21st century
Sources:

Slovenian Environment Agency, 2020 (20/04/2021)

Note:

The timeline of change in average annual cooling degree days in Slovenia over the 21st century for three scenarios relative to the reference period 1981-2010. Bold coloured curves show smoothed model median and lighter colours show model spread.

Figure PP11-5: Projected change in annual heating degree days in Slovenia and the associated reliability of change for 30-year periods relative to the 1981-2010 average
Sources:

Slovenian Environment Agency, 2020 (20/04/2021)

Figure PP11-6: Projected change in average annual cooling degree days in Slovenia and the associated reliability of change for 30-year periods relative to the 1981-2010 average
Sources:

Slovenian Environment Agency, 2021 (20/04/2021)

Figure PP11-7: Projected linear trend in heating and cooling degree days in Europe  over the period 1981-2100
Sources:

European Environment Agency, 2019 (15/04/2019)

Methodology

Other sources and literature

  1. Agencija RS za okolje, 2021. Temperaturni primanjkljaj in presežek ter kurilna sezona 1961-2023.
  2. Evropska agencija za okolje, 2021. Heating and cooling degree days.
  3. IPCC, 2014a: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Field, C.B., V.R. Barros, D.J. Dokken, K.J. Mach, M.D. Mastrandrea, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1132 pp.
  4. IPCC, 2014c: Europe. Kovats, R.S., R. Valentini, L.M. Bouwer, E. Georgopoulou, D. Jacob, E. Martin, M. Rounsevell, and J.-F. Soussana, 2014: Europe. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Barros, V.R., C.B. Field, D.J. Dokken, M.D. Mastrandrea, K.J. Mach, T.E. Bilir, M. Chatterjee, K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 1267-1326.

Last modified
26.09.2025
Author(s)

Ana Car, Živa Vlahović in Gregor Vertačnik, Slovenian Environment Agency