diff --git a/examples/heat_pump/heat_pump.py b/examples/heat_pump/heat_pump.py
new file mode 100644
index 00000000..ca9e36e7
--- /dev/null
+++ b/examples/heat_pump/heat_pump.py
@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+"""
+author: pyosch
+"""
+import pandas as pd
+import numpy as np
+import oemof.thermal.heat_pump as heat_pump
+
+
+# generate test data
+temperature = pd.DataFrame(np.random.randint(-10, 20, size=(96, 1)),
+                           columns=["temperature"],
+                           index=pd.date_range(start='2017', periods=96,
+                                               freq='15 min', name='index'))
+
+print(temperature.head())
+
+# cop calculation for heat pumps
+cop = heat_pump.get_cop(temperature.temperature)
+
+print(cop.head())
diff --git a/oemof_heat_components/heat_pump/heat_pump.py b/oemof_heat_components/heat_pump/heat_pump.py
deleted file mode 100644
index e69de29b..00000000
diff --git a/oemof_heat_components/solar_thermal_collectors.py b/oemof_heat_components/solar_thermal_collectors.py
deleted file mode 100644
index 4ad4d9dc..00000000
--- a/oemof_heat_components/solar_thermal_collectors.py
+++ /dev/null
@@ -1,12 +0,0 @@
-# -*- coding: utf-8 -*-
-
-"""Solar thermal collectors
-
-authors:
-
-SPDX-License-Identifier: GPL-3.0-or-later
-"""
-
-from oemof import solph
-
-my_bus = solph.Bus(label='my_bus')
diff --git a/oemof_heat_components/variable_chp/__init__.py b/oemof_heat_components/variable_chp/__init__.py
deleted file mode 100644
index e69de29b..00000000
diff --git a/oemof_heat_components/variable_chp/variable_chp.csv b/oemof_heat_components/variable_chp/variable_chp.csv
deleted file mode 100644
index 55952149..00000000
--- a/oemof_heat_components/variable_chp/variable_chp.csv
+++ /dev/null
@@ -1,193 +0,0 @@
-timestep,demand_el,demand_th
-3001,219326.3596653,0.1727238027
-3002,216566.3764352,0.1878310716
-3003,217332.5256261,0.1804246049
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-3006,265447.6178909,0.3986349305
-3007,292641.298814,0.4266527212
-3008,308153.512253,0.4065678067
-3009,313124.2512812,0.3898818859
-3010,320001.1325737,0.3657894985
-3011,326901.0906491,0.3492507454
-3012,326762.6299519,0.3378068049
-3013,323808.8017457,0.3317344638
-3014,317698.0696442,0.3280835878
-3015,312330.4099508,0.3303205282
-3016,302315.0861892,0.3414078718
-3017,301364.3227354,0.3597969674
-3018,300607.4042575,0.3795626418
-3019,298387.4177463,0.393969169
-3020,289147.4738889,0.402659952
-3021,281107.5227402,0.3951436745
-3022,263864.5505866,0.3557170404
-3023,241936.9915123,0.289906173
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-3025,221458.6544017,0.176145504
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-3080,193563.4392796,0.45003881
-3081,201778.773978,0.4314186515
-3082,208461.8102945,0.4047128425
-3083,216903.2974649,0.3863368793
-3084,212500.2472951,0.3736651606
-3085,201921.8500317,0.3669524449
-3086,195100.3530181,0.3629396868
-3087,191518.8363181,0.3654698053
-3088,191758.8348598,0.3777770604
-3089,200108.0148989,0.3981098319
-3090,212043.3269945,0.4199995992
-3091,216566.3764352,0.4359055781
-3092,218878.6700778,0.4454633049
-3093,225815.5510058,0.4370591029
-3094,224906.3257611,0.3933397023
-3095,207095.6647491,0.3202250984
-3096,196572.6517646,0.2379952465
-3097,192483.4458417,0.1751658076
-3098,191449.6059695,0.1904818768
-3099,193900.3603093,0.1829832869
-3100,202734.1527884,0.2009174429
-3101,214461.7738383,0.2716427465
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-3103,276778.3182755,0.4327836573
-3104,293264.3719512,0.4123986666
-3105,297427.4235793,0.3954546647
-3106,302795.0832727,0.3710120728
-3107,307982.7440598,0.3542275156
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-3109,304858.1476605,0.3364606117
-3110,294759.7474806,0.3327609373
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-3112,280465.9881766,0.3462873729
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-3114,284273.6573487,0.3849878687
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-3118,255335.3716413,0.3607671813
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-3120,217849.4455622,0.2184803133
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-3122,207455.6625617,0.118857931
-3123,209034.1145094,0.115470415
-3124,216510.9921563,0.1284898265
-3125,227246.3115431,0.1949240462
-3126,254352.3006914,0.3111847349
-3127,279141.3808404,0.3627909661
-3128,290185.9291176,0.3288837741
-3129,292142.8403042,0.3061464629
-3130,296250.5076534,0.2833839939
-3131,300533.5585524,0.2663462221
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-3133,290421.3123028,0.2458779321
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-3135,287130.5630668,0.2308690131
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-3137,285353.6507866,0.2437342604
-3138,288381.3246979,0.2587521015
-3139,288464.4011162,0.2797348083
-3140,280447.5267504,0.2985990013
-3141,276422.9358194,0.3021621826
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-3164,273764.4904339,0.2547330317
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-3178,220849.4273341,0.1983533623
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-3185,213321.7807649,0.1706334702
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-3187,219963.2788723,0.1957283711
-3188,218758.6708069,0.208957016
-3189,221246.3479993,0.2116263567
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-3191,202244.9249918,0.1569039713
-3192,191648.0663021,0.1118200156
diff --git a/oemof_heat_components/variable_chp/variable_chp.py b/oemof_heat_components/variable_chp/variable_chp.py
deleted file mode 100644
index 2534e143..00000000
--- a/oemof_heat_components/variable_chp/variable_chp.py
+++ /dev/null
@@ -1,363 +0,0 @@
-# -*- coding: utf-8 -*-
-"""
-General description
--------------------
-This example is not a real use case of an energy system but an example to show
-how a combined heat and power plant (chp) with an extraction turbine works in
-contrast to a chp (eg. block device) with a fixed heat fraction. Both chp plants
-distribute power and heat to a separate heat and power Bus with a heat and power
-demand. The i/o balance plot shows that the fixed chp plant produces heat and
-power excess and therefore needs more natural gas. The bar plot just shows the
-difference in the usage of natural gas.
-
-Requirements
-------------
-pip install "oemof>=0.2,<0.3"
-pip install matplotlib (to see the bar plot)
-pip install git+https://github.com/oemof/oemof_visio.git (to see the i/o balance
- plot)
-
-Installation requirements
--------------------------
-This example requires the latest version of oemof and matplotlib. Install by:
-
-    pip install oemof
-    pip install oemof
-
-"""
-
-__copyright__ = "oemof developer group"
-__license__ = "GPLv3"
-
-###############################################################################
-# imports
-###############################################################################
-
-# Outputlib
-from oemof import outputlib
-
-# Default logger of oemof
-from oemof.tools import logger
-from oemof.tools import helpers
-import oemof.solph as solph
-
-# import oemof base classes to create energy system objects
-import logging
-import os
-import pandas as pd
-import matplotlib.pyplot as plt
-
-# import oemof plots
-try:
-    from oemof_visio import plot as oeplot
-except ImportError:
-    oeplot = None
-
-
-def shape_legend(node, reverse=True, **kwargs):
-    handels = kwargs['handles']
-    labels = kwargs['labels']
-    axes = kwargs['ax']
-    parameter = {}
-
-    new_labels = []
-    for label in labels:
-        label = label.replace('(', '')
-        label = label.replace('), flow)', '')
-        label = label.replace(node, '')
-        label = label.replace(',', '')
-        label = label.replace(' ', '')
-        new_labels.append(label)
-    labels = new_labels
-
-    parameter['bbox_to_anchor'] = kwargs.get('bbox_to_anchor', (1, 0.5))
-    parameter['loc'] = kwargs.get('loc', 'center left')
-    parameter['ncol'] = kwargs.get('ncol', 1)
-    plotshare = kwargs.get('plotshare', 0.9)
-
-    if reverse:
-        handels.reverse()
-        labels.reverse()
-
-    box = axes.get_position()
-    axes.set_position([box.x0, box.y0, box.width * plotshare, box.height])
-
-    parameter['handles'] = handels
-    parameter['labels'] = labels
-    axes.legend(**parameter)
-    return axes
-
-
-def write_lp_file():
-    filename = os.path.join(
-        helpers.extend_basic_path('lp_files'), 'variable_chp.lp')
-    logging.info('Store lp-file in {0}.'.format(filename))
-    om.write(filename, io_options={'symbolic_solver_labels': True})
-
-
-logger.define_logging()
-logging.info('Initialize the energy system')
-
-# create time index for 192 hours in May.
-date_time_index = pd.date_range('5/5/2012', periods=192, freq='H')
-
-energysystem = solph.EnergySystem(timeindex=date_time_index)
-
-# Read data file with heat and electrical demand (192 hours)
-full_filename = os.path.join(os.path.dirname(__file__), 'variable_chp.csv')
-data = pd.read_csv(full_filename, sep=",")
-
-##########################################################################
-# Create oemof.solph objects
-##########################################################################
-logging.info('Create oemof.solph objects')
-
-# container for instantiated nodes
-noded = {}
-
-# create natural gas bus
-noded['bgas'] = solph.Bus(label="natural_gas")
-
-# create commodity object for gas resource
-noded['rgas'] = solph.Source(
-    label='rgas', outputs={noded['bgas']: solph.Flow(variable_costs=50)})
-
-# create two electricity buses and two heat buses
-noded['bel'] = solph.Bus(label="electricity")
-noded['bel2'] = solph.Bus(label="electricity_2")
-noded['bth'] = solph.Bus(label="heat")
-noded['bth2'] = solph.Bus(label="heat_2")
-
-# create excess components for the elec/heat bus to allow overproduction
-noded['excess_bth_2'] = solph.Sink(
-    label='excess_bth_2', inputs={noded['bth2']: solph.Flow()})
-noded['excess_therm'] = solph.Sink(
-    label='excess_therm', inputs={noded['bth']: solph.Flow()})
-noded['excess_bel_2'] = solph.Sink(
-    label='excess_bel_2', inputs={noded['bel2']: solph.Flow()})
-noded['excess_elec'] = solph.Sink(
-    label='excess_elec', inputs={noded['bel']: solph.Flow()})
-
-# create simple sink object for electrical demand for each electrical bus
-noded['demand_elec'] = solph.Sink(
-    label='demand_elec', inputs={noded['bel']: solph.Flow(
-        actual_value=data['demand_el'], fixed=True, nominal_value=1)})
-noded['demand_el_2'] = solph.Sink(
-    label='demand_el_2', inputs={noded['bel2']: solph.Flow(
-        actual_value=data['demand_el'], fixed=True, nominal_value=1)})
-
-# create simple sink object for heat demand for each thermal bus
-noded['demand_therm'] = solph.Sink(
-    label='demand_therm', inputs={noded['bth']: solph.Flow(
-        actual_value=data['demand_th'], fixed=True, nominal_value=741000)})
-noded['demand_therm_2'] = solph.Sink(
-    label='demand_th_2', inputs={noded['bth2']: solph.Flow(
-        actual_value=data['demand_th'], fixed=True, nominal_value=741000)})
-
-# This is just a dummy transformer with a nominal input of zero
-noded['fixed_chp_gas'] = solph.Transformer(
-    label='fixed_chp_gas',
-    inputs={noded['bgas']: solph.Flow(nominal_value=0)},
-    outputs={noded['bel']: solph.Flow(), noded['bth']: solph.Flow()},
-    conversion_factors={noded['bel']: 0.3, noded['bth']: 0.5})
-
-# create a fixed transformer to distribute to the heat_2 and elec_2 buses
-noded['fixed_chp_gas_2'] = solph.Transformer(
-    label='fixed_chp_gas_2',
-    inputs={noded['bgas']: solph.Flow(nominal_value=10e10)},
-    outputs={noded['bel2']: solph.Flow(), noded['bth2']: solph.Flow()},
-    conversion_factors={noded['bel2']: 0.3, noded['bth2']: 0.5})
-
-# create a fixed transformer to distribute to the heat and elec buses
-noded['variable_chp_gas'] = solph.components.ExtractionTurbineCHP(
-    label='variable_chp_gas',
-    inputs={noded['bgas']: solph.Flow(nominal_value=10e10)},
-    outputs={noded['bel']: solph.Flow(), noded['bth']: solph.Flow()},
-    conversion_factors={noded['bel']: 0.3, noded['bth']: 0.5},
-    conversion_factor_full_condensation={noded['bel']: 0.5}
-    )
-
-##########################################################################
-# Optimise the energy system
-##########################################################################
-
-logging.info('Optimise the energy system')
-
-energysystem.add(*noded.values())
-
-om = solph.Model(energysystem)
-
-# If uncomment the following line you can store the lp file but you should use
-# less timesteps (3) to make it better readable and smaller.
-# write_lp_file()
-
-logging.info('Solve the optimization problem')
-om.solve(solver='cbc', solve_kwargs={'tee': False})
-
-results = outputlib.processing.results(om)
-
-##########################################################################
-# Plot the results
-##########################################################################
-
-myresults = outputlib.views.node(results, 'natural_gas')
-myresults = myresults['sequences'].sum(axis=0)
-myresults = myresults.drop(myresults.index[0]).reset_index(drop=True)
-myresults.rename({0: 'fixed', 1: 'variable', 2: 'total'}, inplace=True)
-myresults.plot(kind='bar', rot=0, title="Usage of natural gas")
-plt.show()
-
-# Create a plot with 6 tiles that shows the difference between the
-# Transformer and the ExtractionTurbineCHP used for chp plants.
-smooth_plot = True
-
-if oeplot:
-    logging.info('Plot the results')
-
-    cdict = {
-        (('variable_chp_gas', 'electricity'), 'flow'): '#42c77a',
-        (('fixed_chp_gas_2', 'electricity_2'), 'flow'): '#20b4b6',
-        (('fixed_chp_gas', 'electricity'), 'flow'): '#20b4b6',
-        (('fixed_chp_gas', 'heat'), 'flow'): '#20b4b6',
-        (('variable_chp_gas', 'heat'), 'flow'): '#42c77a',
-        (('heat', 'demand_therm'), 'flow'): '#5b5bae',
-        (('heat_2', 'demand_th_2'), 'flow'): '#5b5bae',
-        (('electricity', 'demand_elec'), 'flow'): '#5b5bae',
-        (('electricity_2', 'demand_el_2'), 'flow'): '#5b5bae',
-        (('heat', 'excess_therm'), 'flow'): '#f22222',
-        (('heat_2', 'excess_bth_2'), 'flow'): '#f22222',
-        (('electricity', 'excess_elec'), 'flow'): '#f22222',
-        (('electricity_2', 'excess_bel_2'), 'flow'): '#f22222',
-        (('fixed_chp_gas_2', 'heat_2'), 'flow'): '#20b4b6'}
-
-    fig = plt.figure(figsize=(18, 9))
-    plt.rc('legend', **{'fontsize': 13})
-    plt.rcParams.update({'font.size': 13})
-    fig.subplots_adjust(left=0.07, bottom=0.12, right=0.86, top=0.93,
-                        wspace=0.03, hspace=0.2)
-
-    # subplot of electricity bus (fixed chp) [1]
-    electricity_2 = outputlib.views.node(results, 'electricity_2')
-    x_length = len(electricity_2['sequences'].index)
-    myplot = oeplot.io_plot(
-        bus_label='electricity_2', df=electricity_2['sequences'],
-        cdict=cdict, smooth=smooth_plot,
-        line_kwa={'linewidth': 4}, ax=fig.add_subplot(3, 2, 1),
-        inorder=[(('fixed_chp_gas_2', 'electricity_2'), 'flow')],
-        outorder=[(('electricity_2', 'demand_el_2'), 'flow'),
-                  (('electricity_2', 'excess_bel_2'), 'flow')])
-    myplot['ax'].set_ylabel('Power in MW')
-    myplot['ax'].set_xlabel('')
-    myplot['ax'].get_xaxis().set_visible(False)
-    myplot['ax'].set_xlim(0, x_length)
-    myplot['ax'].set_title("Electricity output (fixed chp)")
-    myplot['ax'].legend_.remove()
-
-    # subplot of electricity bus (variable chp) [2]
-    electricity = outputlib.views.node(results, 'electricity')
-    myplot = oeplot.io_plot(
-        bus_label='electricity', df=electricity['sequences'],
-        cdict=cdict, smooth=smooth_plot,
-        line_kwa={'linewidth': 4}, ax=fig.add_subplot(3, 2, 2),
-        inorder=[(('fixed_chp_gas', 'electricity'), 'flow'),
-                 (('variable_chp_gas', 'electricity'), 'flow')],
-        outorder=[(('electricity', 'demand_elec'), 'flow'),
-                  (('electricity', 'excess_elec'), 'flow')])
-    myplot['ax'].get_yaxis().set_visible(False)
-    myplot['ax'].set_xlabel('')
-    myplot['ax'].get_xaxis().set_visible(False)
-    myplot['ax'].set_title("Electricity output (variable chp)")
-    myplot['ax'].set_xlim(0, x_length)
-    shape_legend('electricity', plotshare=1, **myplot)
-
-    # subplot of heat bus (fixed chp) [3]
-    heat_2 = outputlib.views.node(results, 'heat_2')
-    myplot = oeplot.io_plot(
-        bus_label='heat_2', df=heat_2['sequences'],
-        cdict=cdict, smooth=smooth_plot,
-        line_kwa={'linewidth': 4}, ax=fig.add_subplot(3, 2, 3),
-        inorder=[(('fixed_chp_gas_2', 'heat_2'), 'flow')],
-        outorder=[(('heat_2', 'demand_th_2'), 'flow'),
-                  (('heat_2', 'excess_bth_2'), 'flow')])
-    myplot['ax'].set_ylabel('Power in MW')
-    myplot['ax'].set_ylim([0, 600000])
-    myplot['ax'].get_xaxis().set_visible(False)
-    myplot['ax'].set_title("Heat output (fixed chp)")
-    myplot['ax'].set_xlim(0, x_length)
-    myplot['ax'].legend_.remove()
-
-    # subplot of heat bus (variable chp) [4]
-    heat = outputlib.views.node(results, 'heat')
-    myplot = oeplot.io_plot(
-        bus_label='heat', df=heat['sequences'],
-        cdict=cdict, smooth=smooth_plot,
-        line_kwa={'linewidth': 4}, ax=fig.add_subplot(3, 2, 4),
-        inorder=[(('fixed_chp_gas', 'heat'), 'flow'),
-                 (('variable_chp_gas', 'heat'), 'flow')],
-        outorder=[(('heat', 'demand_therm'), 'flow'),
-                  (('heat', 'excess_therm'), 'flow')])
-    myplot['ax'].set_ylim([0, 600000])
-    myplot['ax'].get_yaxis().set_visible(False)
-    myplot['ax'].get_xaxis().set_visible(False)
-    myplot['ax'].set_title("Heat output (variable chp)")
-    myplot['ax'].set_xlim(0, x_length)
-    shape_legend('heat', plotshare=1, **myplot)
-
-    if smooth_plot:
-        style = None
-    else:
-        style = 'steps-mid'
-
-    # subplot of efficiency (fixed chp) [5]
-    fix_chp_gas2 = outputlib.views.node(results, 'fixed_chp_gas_2')
-    ngas = fix_chp_gas2['sequences'][
-        (('natural_gas', 'fixed_chp_gas_2'), 'flow')]
-    elec = fix_chp_gas2['sequences'][
-        (('fixed_chp_gas_2', 'electricity_2'), 'flow')]
-    heat = fix_chp_gas2['sequences'][(('fixed_chp_gas_2', 'heat_2'), 'flow')]
-    e_ef = elec.div(ngas)
-    h_ef = heat.div(ngas)
-    df = pd.DataFrame(pd.concat([h_ef, e_ef], axis=1))
-    my_ax = df.reset_index(drop=True).plot(
-        drawstyle=style, ax=fig.add_subplot(3, 2, 5), linewidth=2)
-    my_ax.set_ylabel('efficiency')
-    my_ax.set_ylim([0, 0.55])
-    my_ax.set_xlabel('May 2012')
-    my_ax = oeplot.set_datetime_ticks(my_ax, df.index, tick_distance=24,
-                                      date_format='%d', offset=12,
-                                      tight=True)
-    my_ax.set_title('Efficiency (fixed chp)')
-    my_ax.legend_.remove()
-
-    # subplot of efficiency (variable chp) [6]
-    var_chp_gas = outputlib.views.node(results, 'variable_chp_gas')
-    ngas = var_chp_gas['sequences'][
-        (('natural_gas', 'variable_chp_gas'), 'flow')]
-    elec = var_chp_gas['sequences'][
-        (('variable_chp_gas', 'electricity'), 'flow')]
-    heat = var_chp_gas['sequences'][(('variable_chp_gas', 'heat'), 'flow')]
-    e_ef = elec.div(ngas)
-    h_ef = heat.div(ngas)
-    e_ef.name = 'electricity           '
-    h_ef.name = 'heat'
-    df = pd.DataFrame(pd.concat([h_ef, e_ef], axis=1))
-    my_ax = df.reset_index(drop=True).plot(
-        drawstyle=style, ax=fig.add_subplot(3, 2, 6), linewidth=2)
-    my_ax.set_ylim([0, 0.55])
-    my_ax = oeplot.set_datetime_ticks(my_ax, df.index, tick_distance=24,
-                                      date_format='%d', offset=12,
-                                      tight=True)
-    my_ax.get_yaxis().set_visible(False)
-    my_ax.set_xlabel('May 2012')
-
-    my_ax.set_title('Efficiency (variable chp)')
-    my_box = my_ax.get_position()
-    my_ax.set_position([my_box.x0, my_box.y0, my_box.width * 1, my_box.height])
-    my_ax.legend(loc='center left', bbox_to_anchor=(1, 0.5), ncol=1)
-
-    plt.show()
-
-else:
-    logging.warning("You have to install 'oemof-visio' to see the i/o-plot")
-    logging.warning(
-        "Use: pip install git+https://github.com/oemof/oemof_visio.git")
diff --git a/oemof_heat_components/__init__.py b/src/oemof/thermal/__init__.py
similarity index 100%
rename from oemof_heat_components/__init__.py
rename to src/oemof/thermal/__init__.py
diff --git a/src/oemof/thermal/heat_pump.py b/src/oemof/thermal/heat_pump.py
new file mode 100644
index 00000000..e0290dc5
--- /dev/null
+++ b/src/oemof/thermal/heat_pump.py
@@ -0,0 +1,56 @@
+# -*- coding: utf-8 -*-
+import pandas as pd
+import warnings
+
+
+def get_cop(temperature, heatpump_type="Air", water_temp=60):
+    """ Calculation of the coefficient of performance depending
+    on the outside temperature
+
+    Parameters
+    ----------
+    temperature: time series
+        containing the outside temperature
+    heatpump_type: string
+        defines the technology used. Ground is more efficient than Air.
+    water_temp: int
+        temperature needed for the heating system
+
+    References
+    ----------
+    ..  [1]: 'https://www.researchgate.net/publication/
+            255759857_A_review_of_domestic_heat_pumps'
+        Research paper about domestic heatpumps, containing the formulas used
+    """
+
+    cop_lst = []
+
+    if heatpump_type == "Air":
+        for tmp in temperature:
+            if (water_temp - tmp) < 15 or (water_temp - tmp) > 60:
+                msg = "'{0}'°C exceeds the limit of the formula used:\
+                15 <= (water_temp - tmp) <= 60"
+                warnings.warn(msg.format((water_temp - tmp)))
+
+            cop = (6.81 - 0.121 * (water_temp - tmp)
+                   + 0.00063 * (water_temp - tmp)**2)
+            cop_lst.append(cop)
+
+    elif heatpump_type == "Ground":
+        for tmp in temperature:
+            if (water_temp - tmp) < 20 or (water_temp - tmp) > 60:
+                msg = "'{0}'°C exceeds the limit of the formula used:\
+                20 <= (water_temp - tmp) <= 60"
+                warnings.warn(msg.format((water_temp - tmp)))
+
+            cop = (8.77 - 0.15 * (water_temp - tmp)
+                   + 0.000734 * (water_temp - tmp)**2)
+            cop_lst.append(cop)
+
+    else:
+        msg = "'{0}' is not a valid heatpump type. Use 'Air' or 'Ground'."
+        raise ValueError(msg.format(heatpump_type))
+
+    cop = pd.DataFrame({"cop": cop_lst}, index=temperature.index)
+
+    return cop