---
title: "Household electricity cost by region and appliance"
method: POST
path: "/v1/electricity-cost"
tags: ["Calculators"]
---

# Household electricity cost by region and appliance

`POST /v1/electricity-cost`

## Request

- Base URL: `https://api.calculate.co.nz`
- URL: `https://api.calculate.co.nz/v1/electricity-cost`
- Auth: API key in header `X-API-Key`

What a New Zealand household pays for power.

The arithmetic is kilowatts times hours times rate, which any model does
unaided. What it cannot know is the New Zealand price data: Wellington pays
34.61c a unit and Balclutha 48.93c, a 41% spread across one small country,
from MBIE's Quarterly Survey of Domestic Electricity Prices.

**The fixed charge is why a bill is never just usage.** Every connection
carries a daily charge whatever you use, so a low user pays a larger share
of their bill simply for being connected. It is returned separately from
the usage cost, because advice that only addresses usage is aiming at part
of the target. The low fixed charge regulations are being phased out in
steps rather than scrapped: capped at $1.80 a day from 1 April 2026 and
revoked on 1 April 2027.

biggest_users is the field to lead with. A heat pump and a hot water
cylinder dominate almost every bill, and standby power almost never does,
which is the opposite of where most saving advice points.

The household multiplier is a model, not a measurement: it scales a typical
appliance profile from 0.60 for one person to 1.30 for five or more. Anyone
who knows their own usage should pass appliance_hours instead.

## Request body

- ElectricityCostRequest
  - `region` string: One of the MBIE survey towns, or "nz average". Case insensitive. The spread is wide: Wellington 34.61c against Balclutha 48.93c.
  - `household_size` integer: 1 to 5, where 5 means five or more. Scales the appliance profile.
  - `daily_fixed_charge` number: The daily connection charge in DOLLARS, from your bill. Typically $0.30 to $2.50. Charged whatever you use.
  - `custom_rate_cents` number: Your own rate in cents per kWh including GST. Overrides the region.
  - `appliance_hours` object, nullable: Override any appliance's daily hours, keyed by heat_pump, hot_water, oven, clothes_dryer, ev_charger, fridge_freezer, dishwasher, washing_machine, stovetop, induction_cooktop, tv, computer, lights, electric_heater.

## Response `200`

Daily, monthly and annual cost, with the appliances ranked.

- ElectricityCostResponse
  - `result` ElectricityCostResult, required
    - `region` string, required: Region used.
    - `rate_cents_per_kwh` number, required: Unit rate applied, including GST.
    - `rate_source` string, required: Where that rate came from.
    - `household_size` integer, required: People in the household.
    - `household_multiplier` number, required: Scale applied to the appliance profile.
    - `daily_kwh_before_multiplier` number, required: Raw appliance total.
    - `daily_kwh` number, required: After the household multiplier.
    - `daily_usage_cost` number, required: Energy cost a day.
    - `daily_fixed_charge` number, required: The connection charge, kept separate because advice that only addresses usage is aiming at part of the bill.
    - `daily_total` number, required: Usage plus fixed charge.
    - `monthly_total` number, required: Daily total over 30.4 days.
    - `annual_total` number, required: Daily total over 365 days.
    - `annual_kwh` number, required: Energy used in a year.
    - `appliances` ElectricityApplianceRow[], required: Every appliance with its own cost.
      - `name` string, required: Appliance.
      - `watts` integer, required: Rated power draw.
      - `hours_per_day` number, required: Hours run a day.
      - `kwh_per_day` number, required: Energy used a day.
      - `daily_cost` number, required: What it costs a day at your rate.
      - `annual_cost` number, required: What it costs a year.
    - `biggest_users` string[], required: The three costing the most a year, which is where any saving is.
    - `nz_average_rate` number, required: MBIE's national figure.
    - `annual_at_nz_average` number, required: The same household at the national rate.
    - `cheapest_region` object, required: Cheapest surveyed town and its rate.
    - `most_expensive_region` object, required: Dearest surveyed town and its rate.
    - `regions_compared` integer, required: How many real towns the comparison covered. MBIE national average is excluded, since it is a figure rather than a place.
    - `saving_against_most_expensive` number, required: Annual difference against the dearest town.
    - `note` string, required: What the fixed charge means for a low user.
  - `disclaimer` string, required: Scope and limits of this calculation.

## Other responses

- `422`: Validation Error

---

[API](https://skmtc.dev/calculate/apis/calculate-co-nz-api.md) · [All operations](https://skmtc.dev/calculate/apis/calculate-co-nz-api/llms.txt) · [OpenAPI document](https://skmtc.dev/calculate/apis/calculate-co-nz-api/revisions/aa59a8e76614?raw)