The Calculator as Lead Magnet: Why a Heat-Pump Cost Tool Pre-Qualifies Better Than a Contact Form | APX Digital

The calculator as lead magnet: why a heat-pump cost tool pre-qualifies better than a contact form

A contact form asks one question: are you a person with a phone number? A calculator asks four that matter, what system, what size, what floor, where, and answers something in return. That exchange is the whole reason we build tools instead of forms. Across the EPC lead-gen sites APX runs, the calculator path is what produced the 780+ leads we've routed to assessors and installers (internal APX aggregate, September 2026).

Here is what the two real tools in our build folder actually ask, measured 3 September 2026, and why each question is a filter.

Tool one: the underfloor heating cost calculator

The UFH tool (/Users/jamiemac/Projects/UFH Cost/index.html, 16,284 bytes) is a three-step funnel. The step indicator is explicit: "Step 1 of 3: System Type", then "Coverage Area", then "Contact Details".

Step 1: which system. Four buttons: Wet UFH (Overlay / Screed), Floor Milling UFH, Electric Mat UFH, Not Sure / Need Advice. This is the qualification. A "wet overlay" click means a screed or board system on a floor being rebuilt or poured, a real project with a real budget. "Electric mat" is usually one bathroom. "Not sure" is a different sales conversation, and the lead email carries that field so nobody phones the wrong conversation.

Step 2: how big and on what. A scope select with m² ranges printed on the options: Single Room / Extension (10–30 m²), Ground Floor Only (40–90 m²), Whole House Retrofit (100+ m²), New Build. Then subfloor: Concrete, Timber Joists, or Anhydrite Screed. Scope converts a looker from a project: nobody types "100+ m² whole-house retrofit" on a Tuesday afternoon for fun. The subfloor question also filters impossible quotes, because milling into an existing concrete slab is a different job to laying mats on timber joists, and the tool forces the choice before contact details are even asked for.

Step 3: where and who. Postcode (labelled "For local pricing") and full name. That's it. No email, no phone.

Then the conversion is the clever part: on submit the tool fires a GA4 generate_lead event with the chosen system as `lead_type`, then opens WhatsApp at the business number with a pre-filled message containing every answer: UFH type, scope, subfloor, postcode, name. The lead arrives in the installer's phone already formatted as a quote brief. There is no "enquiry received, we'll be in touch" black hole.

Tool two: the EPC pre-assessment

The other build (/Users/jamiemac/Projects/epc-pre-assessment/index.html, 29,454 bytes) runs a rules engine in `script.js` against five required fields: postcode, property type (House / Flat / HMO), tenure (private rented / owner occupied / social housing), current EPC band (A to F or Unknown), and benefit status. Then it computes an answer:

• Flats and HMOs get ventilation on the likely-measures list; heat pumps are dropped for flats (you generally can't put one on a second-floor flat).
• Benefit households see a £4,000–£15,000 funding estimate; others see £2,000–£8,000.
• Postcodes starting with B (Birmingham) add solar PV to the measures list.
• Target band is C for benefit households, B otherwise, the escalation logic from the numbers below.

Each of those five fields is a filter with a business reason. Tenure separates landlords (who have a legal deadline) from owner-occupiers (who have a comfort bill). Current EPC band separates "probably fundable now" from "already compliant". Benefit status is the ECO-style funding gate. A contact form gets you a name; this gets you a segment.

Why the numbers behind the questions matter

For a calculator to pre-qualify, its outputs have to be real. Both tools anchor to verified public scheme figures. From GOV.UK's Boiler Upgrade Scheme page, fetched 3 September 2026: £7,500 towards an air source or ground source heat pump, £5,000 towards a biomass boiler, £2,500 towards an air-to-air heat pump, plus an extra £1,500 for off-gas-oil properties until March 2027. From the MEES landlord guidance (same access date): F/G-rated domestic private rentals cannot be let without a registered exemption since 1 April 2020, the landlord cost cap is £3,500 including VAT, and government's stated trajectory is EPC band C for as many privately rented homes as possible by 2030, following a 2026 consultation.

Those two facts change the shape of the leads. A private landlord with an EPC E is a different buyer to a benefit household in a D-terrace, and the tools know it before a human does.

Contact form vs calculator, side by side

The effort is the feature. Somebody who fills in four screens has told you they have a project; somebody who fills in one box has told you they have a keyboard.

Want this built for your trade? APX ships calculator-led funnels as part of lead generation; the tools above are from live builds, not mockups. Info@apxdigital.io · 07753 226214.

Related: anatomy of an EPC lead-gen town page (where the traffic for these tools comes from) and rented lead-gen sites: one business per area.