Works nicely. Some magic numbers should be removed.

.gitignore

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+
+# Created by https://www.toptal.com/developers/gitignore/api/python
+# Edit at https://www.toptal.com/developers/gitignore?templates=python
+
+### Python ###
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+cover/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+.pybuilder/
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+#   For a library or package, you might want to ignore these files since the code is
+#   intended to run in multiple environments; otherwise, check them in:
+# .python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# Cython debug symbols
+cython_debug/
+
+# End of https://www.toptal.com/developers/gitignore/api/python
+
+*.swp
+

ecar.json

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+{
+    "currency": "CHF",	
+    "kwh_price_home": 0.2,
+    "kwh_price_commercial": 0.5,
+    "petrol_litre_price": 1.75,
+    "kilometers_per_year": 20000.0,
+    "years": 6,
+    "ecar": {
+	"label": "Nissan Leaf 2013",
+        "price": 7600,
+        "taxes": 0,
+        "insurance": 354,
+        "kwh_per_kilometer": 0.16,
+        "maintenance": 100,
+	"charging_behaviour": {
+		"percent_free_charges": 90,
+		"percent_home_charges": 5,
+		"percent_commercial_charges": 5
+	}
+    },
+    "ccar": {
+	"label": "Suzuki Grand Vitara 2008",
+        "price": 7000,
+        "taxes": 350,
+        "insurance": 362,
+        "litres_per_kilometer": 0.08,
+        "maintenance": 1000
+    }
+}

ecar.py

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+import matplotlib.pyplot as plt
+import numpy as np
+import json
+import sys
+import argparse
+__author__ = 'm3x1m0m'
+
+class c_settings_extractor:
+    def __init__(self, fname):
+        with open(fname, "r") as rf:
+            settings = json.load(rf)
+            kilometer_price_ccar = settings["ccar"]["litres_per_kilometer"] * settings["petrol_litre_price"]
+            self.labels = [settings["ecar"]["label"], settings["ccar"]["label"]]
+            self.purchase = np.array([settings["ecar"]["price"], settings["ccar"]["price"]])
+            self.taxes = np.array([settings["ecar"]["taxes"], settings["ccar"]["taxes"]])
+            self.insurance = np.array([settings["ecar"]["insurance"], settings["ccar"]["insurance"]])
+            kilometer_price_ecar =  (   settings["ecar"]["charging_behaviour"]["percent_home_charges"] * settings["kwh_price_home"]
+                                      + settings["ecar"]["charging_behaviour"]["percent_commercial_charges"] * settings["kwh_price_commercial"]) / 100.0
+            self.driving = np.array([kilometer_price_ecar * settings["kilometers_per_year"], kilometer_price_ccar * settings["kilometers_per_year"]])
+            self.maintenance = np.array([settings["ecar"]["maintenance"], settings["ccar"]["maintenance"]])
+            self.kilometers = settings["kilometers_per_year"]
+            self.currency = settings["currency"]
+    def get_labels(self):
+        return self.labels
+    def get_purchase(self):
+        return self.purchase
+    def get_taxes(self):
+        return self.taxes
+    def get_insurance(self):
+        return self.insurance
+    def get_driving(self):
+        return self.driving
+    def get_maintenance(self):
+        return self.maintenance
+    def get_kilometers(self):
+        return self.kilometers
+    def get_currency(self):
+        return self.currency
+
+class c_ecar_comparator:
+    def __init__(self, fname):
+        self.settings_extractor = c_settings_extractor(fname)
+    def calculate_costs_a_year(self):
+        taxes = self.settings_extractor.get_taxes()
+        insurance = self.settings_extractor.get_insurance()
+        driving = self.settings_extractor.get_driving()
+        maintenance = self.settings_extractor.get_maintenance()
+        return taxes + insurance + driving + maintenance
+    def calculate_costs(self, years, months):
+        months_a_year = 12.0
+        costs_a_year = self.calculate_costs_a_year()
+        return costs_a_year * (years + months/months_a_year)
+    def calculate_break_even(self):
+        total_costs = self.settings_extractor.get_purchase()
+        months_a_year = 12.0
+        increment = self.calculate_costs_a_year() / months_a_year
+        months = 0
+        while total_costs[0] > total_costs[1]:
+            total_costs = total_costs + increment 
+            months += 1
+        kilometers = self.settings_extractor.get_kilometers() * months / months_a_year
+        return [months//months_a_year, months%months_a_year, kilometers] # years, months
+    def calculate_amortization_point(self):
+        y = 0
+        m = 1
+        months_a_year = 12.0
+        costs_a_month = self.calculate_costs(y, m)
+        savings_a_month = costs_a_month[1]-costs_a_month[0]
+        months_till_amortized = self.settings_extractor.get_purchase()[0] / savings_a_month
+        kilometers = months_till_amortized * self.settings_extractor.get_kilometers() / months_a_year
+        months_till_amortized = np.ceil(months_till_amortized)
+        return months_till_amortized//months_a_year, months_till_amortized%months_a_year, round(kilometers, ndigits=2)
+
+def main():
+    parser = argparse.ArgumentParser(description='This script allows to calculate if an electric car makes sense financially for you.')
+    parser.add_argument('-a','--settings', help='Settings file.', required=True, metavar=('FILENAME'))
+    parser.add_argument('-b','--break_even', help='Calculate the break even point (when the EV becomes cheaper).', action='store_true')
+    parser.add_argument('-c','--amortization', help='Calculate the point in time when the electric vehicle is amortized completely by savings.', action='store_true')
+    parser.add_argument('-d','--savings_per_month', help='Calculate savings per month.', action='store_true')
+    parser.add_argument('-e','--savings_per_year', help='Calculate savings per year.', action='store_true')
+    parser.add_argument('-f','--savings_per_kilometer', help='Calculate savings per 100 kilometers (only driving, no maintenance, taxes or insurance).', action='store_true')
+    parser.add_argument('-g','--plot', help='Visualize costs over one or multiple years.', type=int, metavar=('YEARS'))
+    args = parser.parse_args()
+    if not args.break_even and not args.savings_per_year and not args.savings_per_month and not args.plot:
+        sys.exit("Please choose one or multiple options")
+    comparator = c_ecar_comparator(args.settings)
+    extractor = c_settings_extractor(args.settings)
+    be_years = None
+    be_months = None
+    be_kilometers = None
+    if args.break_even:
+        be_years, be_months, be_kilometers = comparator.calculate_break_even()
+        print("Break even after {} years and {} months.".format(be_years, be_months))
+    if args.savings_per_month:
+        years = 0
+        months = 1
+        savings = comparator.calculate_costs(years, months)
+        print("Savings per month based on yearly spending: {}.".format(round(savings[1]-savings[0], ndigits=2)))
+    if args.savings_per_year:
+        years = 1
+        months = 0
+        savings = comparator.calculate_costs(years, months)
+        print("Savings per year: {}.".format(round(savings[1]-savings[0], ndigits=2)))
+    if args.savings_per_kilometer:
+        hundred_km = 100.0
+        driving = hundred_km * extractor.get_driving() / extractor.get_kilometers() 
+        labels = extractor.get_labels()
+        print("Costs driving 100 km in the {}: {}. Costs driving 100 km in the {}: {}.".format(labels[0], round(driving[0], ndigits=2), labels[1], round(driving[1]), ndigits=2))
+    am_years = None
+    am_months = None
+    am_kilometers = None
+    if args.amortization:
+        am_years, am_months, am_kilometers = comparator.calculate_amortization_point()
+        print("The electric vehicle will be amortized by savings after {} years, {} months or exactely at {} kilometres.".format(am_years, am_months, am_kilometers))
+    if args.plot != None:
+        width = 0.3
+        plt_colors = ["#8ecae6", "#219ebc", "#023047", "#ffb703", "#fb8500"];
+        color_ind = 0
+        labels = extractor.get_labels()
+        purchase = extractor.get_purchase()
+        taxes = extractor.get_taxes()
+        insurance = extractor.get_insurance()
+        driving = extractor.get_driving()
+        maintenance = extractor.get_maintenance()
+        fig, ax = plt.subplots()
+        ax.bar(labels, purchase, width, label = "Price", color = plt_colors[0])
+        current_y = extractor.get_purchase()
+        y = 0
+        for i in range(args.plot):
+            ax.bar(labels, taxes, width, bottom = current_y, label = "Taxes".format(y), color = plt_colors[1])
+            current_y = current_y + taxes
+            ax.bar(labels, insurance, width, bottom = current_y, label = "Insurance".format(y), color = plt_colors[2])
+            current_y = current_y + insurance
+            ax.bar(labels, driving, width, bottom = current_y, label = "Driving".format(y), color = plt_colors[3])
+            current_y = current_y + driving
+            ax.bar(labels, maintenance, width, bottom = current_y, label = "Maintenance".format(y), color = plt_colors[4])
+            current_y = current_y + maintenance
+            y += 1
+        labels = ["Purchase", "Taxes", "Insurance", "Driving", "Maintenance"]
+        if args.break_even:
+            months_a_year = 12.0
+            be_money = (be_years + be_months/months_a_year) * comparator.calculate_costs_a_year()
+            be_money = be_money[1] + extractor.get_purchase()
+            ax.plot(np.linspace(-0.2, 1.2, 10), [be_money[1]]*10, "--", color = plt_colors[2], label = "Break even")
+            ax.text(0.3, be_money[1] + 100, "Break even: {} years, {} months, {} kilometers".format(be_years, be_months, be_kilometers))
+            labels = ["Break even"] + labels
+        if args.amortization:
+            months_a_year = 12.0
+            am_money = (am_years + am_months/months_a_year) * comparator.calculate_costs_a_year()
+            am_money = am_money[1] + extractor.get_purchase()
+            ax.plot(np.linspace(-0.2, 1.2, 10), [am_money[1]]*10, "--", color = plt_colors[2], label = "Amortization")
+            ax.text(0.3, am_money[1] + 100, "Amortization: {} years, {} months, {} kilometers".format(am_years, am_months, am_kilometers))
+            labels = ["Amortization"] + labels
+        ax.set_ylabel(extractor.get_currency())
+        ax.set_title("Comparision of economics electric vs. combustion car")
+        ax.legend(labels)
+        ax.grid(axis = "y")
+        plt.show()
+
+if __name__ == "__main__":
+    main()