Hot Water Sizing and Recommendation Tool | Knowledge Base

Overview

A step-by-step sizing and recommendation tool designed for plumbers, installers, and hot water specialists. The user enters details about the installation site and household, and the tool recommends suitable HPWH products from the platform database with estimated annual running costs, payback period versus the existing system, and available incentive rebates at the installation postcode.

The tool is designed to support a sales conversation with a homeowner or building owner. The output should be clear enough to show a customer directly, not just use as a backend reference. This is one of the key features for the plumber/installer user segment, which is otherwise underserved by the platform’s more technical tools.

User Stories

As a plumber quoting a job, I want to enter the address and basic household details and immediately get a list of suitable HPWH products with running costs so I can put together a professional quote without manual research.
As an installer recommending a system, I want to see the payback period versus the customer’s existing system so I have a simple financial argument to present.
As a plumber, I want to see what government rebates are available at the installation postcode so I can include them in my quote and not miss leaving money on the table.
As a hot water specialist, I want to save the recommendation output as a PDF I can attach to a formal quote.
As a plumber, I want the tool to flag any installation-specific requirements (e.g. clearance requirements for R290 refrigerant in enclosed spaces) so I don’t miss safety requirements at the planning stage.

Inputs

Step 1: Installation location

Postcode (Australian or NZ) — drives climate zone, available scheme rebates, and grid emissions factor
State/territory (auto-populated from postcode)

Step 2: Existing system

Existing system type: gas storage / gas continuous flow / electric storage / existing heat pump / no hot water system (new install)
Existing system capacity (L, for storage systems) — helps right-size the HPWH
Approximate age of existing system (years)

Step 3: Household profile

Number of bedrooms (used as a proxy for occupant count if exact count not known)
Number of occupants (optional, overrides bedroom-based estimate)
Usage pattern: standard / high (e.g. large family with teenagers)
Metered electricity tariff ($/kWh) — flat or time-of-use. User enters from bill.
Gas tariff ($/MJ or $/GJ) — if existing system is gas

Step 4: Installation constraints

Available installation location: outdoor / indoor / garage (affects refrigerant requirements and noise constraints)
Noise sensitivity: standard / high (e.g. near bedrooms) — filters out louder products
Available electrical circuit: existing hot water circuit (240V/10A) / 15A dedicated circuit / three-phase available
Roof or floor space limitations: yes / no (filters out very large units)

Recommendation Engine

The recommendation engine filters and ranks products from the platform database based on:

Capacity match: tank volume appropriate for the estimated daily hot water demand (based on occupant count and usage pattern)
Climate suitability: product operates down to the minimum ambient temperature for the postcode (uses climate zone data)
Installation fit: refrigerant requirements compatible with the installation location (e.g. R290 products require adequate ventilation — flag for enclosed indoor locations)
Electrical compatibility: product compatible with the available circuit
Noise threshold: products below the noise threshold for the installation location

Products that fail any hard constraint (e.g. minimum operating temperature below the location’s design winter ambient) are excluded. Products that fail a soft constraint (e.g. noise preference) are included but flagged.

Ranking

Filtered products are ranked by:

Annual running cost at the entered tariff (lowest first)
Within equal running cost: by payback period vs existing system (shortest first)

Top 3-5 products displayed.

Outputs

Product recommendation cards

Each recommended product shown as a card:

Product name, brand, and image (from product database)
Tank volume (L) and rated capacity (kW)
COP at relevant climate zone ambient temperature
Annual running cost estimate ($)
Annual running cost of existing system ($ comparison)
Annual savings ($/year)
Simple payback period (years, net of available rebates)
Available rebates at the postcode: STC value ($), any applicable state scheme rebate ($), total incentive value ($)
Watermark certification status (green tick if certified)
Installation notes: any flags relevant to the installation constraints (e.g. “R290 refrigerant — ensure adequate ventilation if installing in enclosed space”)
“View full specs” link to the product detail page

Rebate summary

Below the product cards, a plain-English summary of available incentives at the installation postcode:

STC rebate: “This product qualifies for approximately X STCs, worth approximately $XXX at current prices.”
State scheme rebate (if applicable): scheme name, eligibility note, and indicative value
EnergyAE note: “Rebates are indicative. Contact your installer or EnergyAE for a confirmed rebate quote.”

Installation flag panel

A panel showing any installation-specific flags identified from the input constraints:

Refrigerant-specific requirements (ventilation, clearance distances)
Electrical upgrade requirements (if a 15A circuit or dedicated circuit is needed)
Noise flags (if any recommended product exceeds the entered noise threshold)

Export

PDF output: product comparison table, rebate summary, and installation notes — formatted as a quote attachment
Share link: unique URL to the recommendation result, valid for 30 days

Out of Scope (v1)

Commercial or multi-unit residential sizing (single residential dwelling only)
Solar PV self-consumption optimisation
Multi-zone or boost element upgrade-only scenarios
Live rebate API integration (rebate values maintained manually by Alastair for v1)
Automated electrical upgrade cost estimation
Integration with supplier or distributor pricing databases

Data Model (indicative)

sizing_recommendations
  recommendation_id
  user_id (nullable — tool may be accessible without login)
  created_at
  inputs (JSON: postcode, existing system, household profile, installation constraints)
  climate_zone (derived from postcode)
  available_rebates (JSON: STC value, state rebate)
  recommended_products (JSON array: product_id, annual_cost, savings, payback, flags)
  share_token (nullable)
  share_expires_at (nullable)

rebate_config (admin-managed)
  state
  scheme_name
  product_category
  rebate_amount
  rebate_type (flat / per-STC / percentage)
  eligibility_notes
  last_updated
  updated_by

Acceptance Criteria

Open Questions

Should the sizing tool be accessible without a platform login (public access), or require registration? Public access would maximise reach with installers but requires managing rebate data without user context. Alastair to decide before build.
Rebate values change regularly (STC prices fluctuate, state scheme eligibility changes). Who updates the rebate_config table, and how frequently? This is an ongoing operational commitment if the tool is public-facing.
What is the correct minimum ambient temperature threshold for climate suitability filtering? Alastair to provide a reference table of minimum winter ambient by climate zone / postcode region.
Should the noise threshold input be a dB(A) value, or a simpler category (standard / sensitive)? A category is easier for an installer to answer; a dB(A) threshold is more precise but requires the installer to know what’s acceptable.
Is the tool intended for use during a customer conversation (mobile-friendly, quick to fill in) or as a back-office quoting tool (desktop, more detailed)? This affects the UI design priority.