Authentication, input and response

Endpoint

POST https://api.altum.ai/subsidy

Request headers

Header	Required	Value
x-api-key	Yes	Your Altum AI API key
Content-Type	Yes	application/json

The fastest way to see the API working is to send a single field, postcode, and inspect the response.

curl -X POST https://api.altum.ai/subsidy \
  -H "x-api-key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "postcode": "3511 AA"
  }'

This returns all available subsidies for the postcode (municipal, provincial, and national) with Loans.eligible_programs empty and no isde_2026 block.

From here, three usage flows extend the request:

Flow	Add to request	Returns
Discover subsidies	level, limit, tags	Filtered subsidies only
Check loan eligibility	applicant object	Eligible loan programs with calculations
Estimate ISDE subsidy	isde object	isde_2026 calculation block

You can combine all three in a single request.

Returns subsidies, loan eligibility, and ISDE 2026 estimates for a given postcode. The applicant and isde objects are optional. The response always returns the same top-level structure; sections you didn't request return empty arrays or are omitted.

Request body - top level

Field	Type	Required	Description
postcode	string	Yes	Dutch postcode in 1234 AB format (with space).
level	array of strings	No	Filter subsidies by level. One or more of municipality, province, national. Defaults to all three.
limit	integer	No	Maximum number of subsidies returned per level.
tags	array of strings	No	Filter subsidies by topic. See Tags reference.
loan_applicant_profile	object	No	Personal and financial details for loan eligibility. See Applicant object.
isde	object	No	Project details for ISDE 2026 calculation. See ISDE object.

Complete request example

{
  "postcode": "3511 AA",
  "level": ["municipality", "national"],
  "limit": 5,
  "tags": ["Isolatie", "Warmtepompen"],
  "loan_applicant_profile": {
    "age": 45,
    "is_homeowner": true,
    "is_occupant": true,
    "residence_country": "Netherlands",
    "property_use_residential_percent": 100,
    "credit_approved": true,
    "previously_rejected_nwf1": false,
    "rejection_reason": null,
    "requested_amount": 15000,
    "existing_nwf_loan_balance": 0,
    "specific_target_group": false,
    "collective_neighborhood": false,
    "has_mortgage_security": false,
    "business_part_connected": null,
    "gross_household_income": 55000,
    "desired_loan_period_years": 10
  },
    "isde_rvo": {
    "measures": [
      { "code": "WB002a", "area_m2": 80 },
      { "code": "WB212a", "area_m2": 40 },
      { "code": "WB019b", "area_m2": 50 },
      { "code": "WB149c" },
      { "code": "WB157"  },
      { "code": "WB405"  },
      { "code": "WB142a" }
    ]
  }
}

Usage flows

Flow 1 - Discover subsidies only

Send postcode with optional level, limit, and tags. The response returns subsidies grouped by level. Loans.eligible_programs will be empty and the isde_2026 block will be absent.

Request

{
  "postcode": "3511 AA",
  "level": ["municipality", "province", "national"],
  "limit": 5,
  "tags": ["Isolatie", "Warmtepompen"]
}

Response (truncated)

{
  "postal_code": "3511 AA",
  "municipality": "Utrecht",
  "province": "Utrecht",
  "disclaimer": "These subsidies were available at the moment of scraping and may have closed since. Please verify on official websites.",
  "Loans": { "eligible_programs": [] },
  "subsidies": {
    "municipality_subsidies": [
      {
        "location_name": "Utrecht",
        "name": "Vraag subsidie isoleren kleine vve",
        "description": "Deze subsidie van de gemeente Utrecht is bedoeld voor kleine Verenigingen van Eigenaren (VvE's)...",
        "eligibility": "Eigenaar zijn van een woning in een kleine VvE...",
        "application_deadlines": "until:31 december 2026",
        "subsidy_amounts": "min:€8.000 max:€8.000",
        "budget_ceilings": null,
        "application_process": "Maak eventueel een afspraak voor hulp bij de aanvraag...",
        "url": "https://loket.digitaal.utrecht.nl/nl/producten/kleine-vve-isoleren-extra-subsidie-aanvragen",
        "contact_info": "[e-mail], 030 – 286 33 36",
        "level": "municipality"
      }
    ],
    "province_subsidies": [
      {
        "location_name": "Utrecht",
        "name": "Subsidieregeling Bereikbaarheid",
        "description": "De Subsidieregeling Bereikbaarheid van de provincie Utrecht...",
        "eligibility": "Fiets: Wegbeheerders binnen de provincie Utrecht...",
        "application_deadlines": "from:7 januari 2026 to:30 september 2026",
        "subsidy_amounts": null,
        "budget_ceilings": null,
        "application_process": "Dien een projectplanning in met duidelijke mijlpalen...",
        "url": "https://www.provincie-utrecht.nl/loket/subsidies/subsidieregeling-bereikbaarheid",
        "contact_info": "Voor algemene vragen: [e-mail]...",
        "level": "province"
      }
    ],
    "national_subsidies": [
      {
        "location_name": "Netherlands",
        "name": "ISDE: Warmtepomp woningeigenaren",
        "description": "Met de Investeringssubsidie duurzame energie en energiebesparing (ISDE)...",
        "eligibility": "U laat de warmtepomp eerst installeren, daarna vraagt u de subsidie aan...",
        "application_deadlines": "Aanvragen tot en met 31 december 2030.",
        "subsidy_amounts": null,
        "budget_ceilings": null,
        "application_process": "Voor uw aanvraag heeft u de DigiD-app nodig...",
        "url": "https://www.rvo.nl/subsidies-financiering/isde/woningeigenaren/warmtepomp",
        "contact_info": "Ministerie van Economische Zaken en Klimaat",
        "level": "national"
      }
    ]
  }
}

Subsidy entry fields

Field	Type	Description
location_name	string	Municipality, province, or country name.
name	string	Program name (Dutch).
description	string	Program description (Dutch).
eligibility	string	Semicolon-separated eligibility conditions (Dutch).
application_deadlines	string	Deadline string. Formats: until:<date> or from:<date> to:<date>. Dates in Dutch (e.g. 31 december 2026).
subsidy_amounts	string	Amount range string. Format: min:€<amount> max:€<amount>.
budget_ceilings	string	Total budget cap for the program, if specified.
application_process	string	How to apply (Dutch).
url	string	Official program page.
contact_info	string	Contact details for the issuing body.
level	string	One of municipality, province, national.

Flow 2 - Loan eligibility

Add the applicant object to the request. The response returns matching loan programs with applicant-specific calculations (interest rate, monthly payment, total cost).

All fields are required when applicant is provided unless marked otherwise.

Field	Type	Description
age	integer	Applicant's age in years. Some programs (e.g. NWF 1) have age caps.
is_homeowner	boolean	Whether the applicant owns the property.
is_occupant	boolean	Whether the applicant lives in the property.
residence_country	string	Country of residence. Most programs require Netherlands.
property_use_residential_percent	integer	Percentage of the property used for residential purposes (0–100).
credit_approved	boolean	Whether the applicant has passed a credit check.
previously_rejected_nwf1	boolean	Whether the applicant was previously rejected for an NWF 1 loan.
rejection_reason	string | null	Reason for prior rejection, if applicable.
requested_amount	number	Requested loan amount in EUR.
existing_nwf_loan_balance	number	Current outstanding balance on existing NWF loans (EUR).
specific_target_group	boolean	Whether the applicant belongs to a specific target group eligible for special terms.
collective_neighborhood	boolean	Whether the application is part of a collective neighbourhood project.
has_mortgage_security	boolean	Whether a mortgage security is in place.
business_part_connected	boolean | null	Indicates connection to a business part of the property.
gross_household_income	number	Gross annual household income in EUR. Used for income-based interest tiers.
desired_loan_period_years	integer	Requested repayment period in years.

Request

{
  "postcode": "3511 AA",
  "loan_applicant_profile": {
    "age": 45,
    "is_homeowner": true,
    "is_occupant": true,
    "residence_country": "Netherlands",
    "property_use_residential_percent": 100,
    "credit_approved": true,
    "previously_rejected_nwf1": false,
    "rejection_reason": null,
    "requested_amount": 15000,
    "existing_nwf_loan_balance": 0,
    "specific_target_group": false,
    "collective_neighborhood": false,
    "has_mortgage_security": false,
    "business_part_connected": null,
    "gross_household_income": 55000,
    "desired_loan_period_years": 10
  }
}

Response

{
  "postal_code": "3511 AA",
  "municipality": "Utrecht",
  "province": "Utrecht",
  "disclaimer": "These subsidies were available at the moment of scraping and may have closed since. Please verify on official websites.",
  "Loans": {
    "eligible_programs": [
      {
        "program_name": "Energy Savings Loan (NWF 1)",
        "description": "Standard loan for homeowners (≤75 years old) to finance energy-saving home improvements.",
        "min_max_loan_amount": [1000, 28000],
        "max_loan_period_years": 20,
        "interest_type": "Income-based: 0% if household income ≤€60,000, otherwise 3.61% fixed",
        "repayment": "Monthly annuity (up to 20 years; 15 years for heat pumps/batteries if >33% of loan)",
        "key_features": [
          "Requires professional contractor installation",
          "Applies to 18 defined energy-saving measures",
          "Early repayment allowed without penalty (min €250)",
          "No mortgage required; construction deposit used"
        ],
        "loan_amount": 15000,
        "loan_period_years": 10,
        "applied_interest_rate_percent": 0,
        "total_interest": 0,
        "total_cost": 15000,
        "monthly_payment": 125
      },
      {
        "program_name": "Sustainability Loan (Duurzaamheidslening)",
        "description": "A low-interest loan offered through municipalities in collaboration with SVn...",
        "min_max_loan_amount": [2500, 25000],
        "max_loan_period_years": 15,
        "interest_type": "Fixed rate: typically 1.7% for 10 years (loans ≤€7,500) or 15 years (loans >€7,500)",
        "repayment": "Monthly annuity payments; early repayment allowed without penalty.",
        "key_features": [
          "Available only in participating municipalities",
          "Loan amount depends on local program limits",
          "Funds are managed through an SVn building depot for direct payment to contractors",
          "Fixed interest rate for the entire loan term",
          "Requires prior approval (Toewijzingsbrief) from the municipality before applying at SVn",
          "Intended for sustainability measures improving energy efficiency"
        ],
        "applied_interest_rate_percent": 1.7,
        "loan_amount": 15000,
        "loan_period_years": 10,
        "total_interest": 1321.7,
        "total_cost": 16321.7,
        "monthly_payment": 136.01
      }
    ]
  },
  "subsidies": {
    "municipality_subsidies": [],
    "province_subsidies": [],
    "national_subsidies": []
  }
}

Eligible program fields

Field	Type	Description
program_name	string	Loan product name.
description	string	Short summary of the loan product.
min_max_loan_amount	array [min, max]	Allowed loan amount range in EUR.
max_loan_period_years	integer	Maximum repayment period in years.
interest_type	string	Human-readable description of how interest is determined.
repayment	string	Human-readable description of repayment terms.
key_features	array of strings	Bullet points describing the program.
loan_amount	number	Amount applied to this calculation (echoes applicant.requested_amount).
loan_period_years	integer	Period applied to this calculation (echoes applicant.desired_loan_period_years).
applied_interest_rate_percent	number	Interest rate applied for this specific applicant.
total_interest	number	Total interest over the loan period (EUR).
total_cost	number	Principal + total interest (EUR).
monthly_payment	number	Monthly annuity (EUR), rounded to two decimals.

Flow 3 - ISDE 2026 calculation

Add the isde object to the request. The response returns an isde_2026 block with the total subsidy estimate, per-category breakdown

Measure	Codes
Insulation	WB002a, WB002b, WB002c, WB002d, WB002f, WB143, WB001e, WB009a, WB009b, WB009c, WB392, WB207, WB242, WB268, WB361, WB362, WB363, WB004, WB005, WB145, WB212a, WB214b
Glazing	WB019a, WB019b, WB161a, WB147b, WB147c
Heat pump	WB112, WB149a, WB149b, WB149c, WB159, WB198, WB199
Solar boiler	WB136, WB138, WB157
Ventilation	WB405, WB418
District heating connection	WB131
Electric cooking	ES001

By default only the area (area_m2) needs to be supplied to Insulation and Glazing

Request

   {
  "postcode": "3511 AA",
  "isde_rvo": {
    "measures": [
      { "code": "WB002a", "area_m2": 80 },
      { "code": "WB212a", "area_m2": 40 },
      { "code": "WB019b", "area_m2": 50 },
      { "code": "WB149c" },
      { "code": "WB157"  },
      { "code": "WB405"  },
      { "code": "WB142a" }
    ]
  }
}

Response

  {
  "postal_code": "3511 AA",
  "municipality": "Utrecht",
  "province": "Utrecht",
  "disclaimer": "These subsidies were available at the moment of scraping and may have closed since. Please verify on official websites.",
  "Loans": { "eligible_programs": [] },
  "subsidies": {
    "municipality_subsidies": [],
    "province_subsidies": [],
    "national_subsidies": []
  },
 "isde_2026": {
    "total_subsidy_euro": 8525,
    "category_count": 5,
    "eligibility": {
      "insulation": [
        "apply <24 months after installation",
        "only receive one subsidy for cavity wall, facade, floor, roof, attic or attic floor insulation"
      ],
      "glazing": [
        "apply <24 months after installation",
        "you can apply for glass insulation 2 times"
      ],
      "heat_pump": [
        "apply <24 months after installation",
        "entire installation is done by a building installation company",
        "not second-hand products"
      ],
      "solar_boiler": [
        "apply <24 months after installation",
        "entire installation is done by a (construction) installation company",
        "not second-hand products"
      ],
      "ventilation": [
        "installed on or after 1 January 2026",
        "apply <24 months after installation"
      ]
    },
    "breakdown": {
      "insulation": {
        "amount_WB002a": 0,
        "amount_WB212a": 1300
      },
      "glazing": {
        "amount_WB019b": 2250
      },
      "ventilation": {
        "amount_WB405": 400
      },
      "heat_pump_primary": {
        "amount_WB149c": 2825
      },
      "solar_boiler": {
        "amount_WB157": 1750
      }
    },
    "unrecognized_codes": [
      "No ISDE subsidy available for code: WB142a"
    ]
  }
}

isde_2026 object

Field	Type	Description
total_subsidy_euro	number	Sum of all category amounts (EUR).
category_count	integer	Number of categories that returned an amount > 0.
eligibility	object	eligibility and conditions per category group.
breakdown	object	Per-category breakdown. See below.

breakdown

Each category (insulation, glazing, ventilation, heat_pump_primary, heat_pump_extra, solar_boiler, district_heating, electric_cooking) follows the same shape:

breakdown": {
    "category1": { "amount_RVO-code1": 400 },
    "category2": { "amount_RVO-code2": 1750 }
    }

Field	Type	Description
amount_RVO-code	number	Calculated subsidy amount for this category (EUR).

Some RVO codes are not eligible for an ISDE subsidy. In such cases, you may receive the following warning:

"unrecognized_codes": [
      "No ISDE subsidy available for code: WB142a"
    ]

Flow 4 - Combined

Send postcode, applicant, and isde in one request to get subsidies, loans, and ISDE calculation in a single response. The top-level response structure is the same as in the Complete request example.

Tags reference

The tags field filters subsidies by topic. Pass one or more values, exact case-sensitive match, Dutch only.

Sustainability (general) Duurzaamheid, Duurzaamheid en samenleving, Duurzaam ondernemen, Duurzaam bouwen en verbouwen, Duurzaam en slim rijden, Duurzaam financieren, Duurzaam produceren, Duurzaam voedsel, Verduurzamen

Climate & emissions Klimaatadaptatie, Klimaatakkoord, Klimaatbeleid, Klimaatneutraal, Klimaatverandering, CO2, CO2-neutraal, CO2-opslag, CO2-reductie, Emissiereductie, Emissie, Emissiehandel, Niet-CO2-broeikasgassen

Air quality Fijn stof, Luchtkwaliteit, NOx-beperkende technieken, Stikstof

Renewable energy Hernieuwbare energie, Duurzame energie, Duurzame energievoorziening, Duurzame elektriciteit, Zonnepanelen, Zon-PV-installaties, Zonneboilers, Wind, Wind op land, Wind op zee, Windmolens, Windturbines, Waterstof, Waterstofcellen, Biomassaketels, Groen gas, Aardgasvrij, Energie uit water, Bodemenergie

Energy efficiency & buildings Energiebesparing, Energieopslag, Opslag van elektriciteit, Netcongestie, Isolatie, Isoleren, Warmtepompen, Warmte Koude Opslag, Duurzame warmte en koude, Ledverlichting, Ventilatie en binnenmilieu, Gebouwde omgeving

Circular economy & materials Circulair ondernemen, Biobased economy, Biobased materialen, Afval, Grondstoffen, Valorisatie

Nature & environment Natuur, Natuurbeheer, Natuurterreinen, Bodem, Oppervlaktewater, Grondwater, Verontreiniging, Lucht, Milieu, Milieuzorg, Eco-activiteiten

Mobility & innovation Duurzame mobiliteit, Duurzame ontwikkeling, Duurzame technologie, Duurzame innovatie, Elektrisch rijden, Mobiliteit en ruimte

UN SDGs SDG7 Betaalbare en duurzame energie, SDG11 Duurzame steden en gemeenschappen, SDG12 Verantwoorde consumptie en productie, SDG13 Klimaatactie, SDG14 Leven in het water, SDG15 Leven op het land

200: OK Standard response

Successful response.

400: Bad Request Unsuccessful response

404 Not Found

500: Internal Server Error Service is not available and/or down