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How We Built a Free Energy Rebate Calculator for US Homeowners

#webdev #php #energy #opensource

How We Built a Free Energy Rebate Calculator for US Homeowners

The Inflation Reduction Act and subsequent energy legislation created billions in rebate programs for US homeowners. But finding out what you actually qualify for? That remained frustratingly complex.

We built Energy Rebate Calculator to solve this.

The Problem

Energy rebate programs in the US are a maze:

  • Federal rebates (IRA, HOMES Act, HEEHR)
  • State-level programs (50 states, each different)
  • Utility company rebates (thousands of utilities)
  • Income-based eligibility (AMI thresholds vary by county)

A homeowner in Texas faces completely different incentives than one in California. Even within a state, your county's Area Median Income changes your eligibility.

Architecture Decisions

PHP 8.1, No Framework, No Database

We chose a deliberately simple stack:

  • PHP 8.1 with strict typing
  • Static JSON data files for rebate programs
  • File-based HTML caching (24h TTL)
  • No database — zero maintenance overhead

Why no database? The rebate data changes quarterly at most. Serving from cached HTML files means near-instant response times and zero database security surface.

Data Structure

Each state has a structured data file containing program details:

state: california
programs:
  - name: TECH Clean California
    type: heat_pump
    amount: $3,000
    income_limit: none
    source: California Energy Commission
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The calculator cross-references federal + state + local programs based on user inputs.

111 Pages, Zero Bloat

  • 50 state pages with state-specific rebate details
  • 45 educational articles on energy efficiency
  • Category pages (heat pumps, solar, insulation, weatherization)
  • Legal pages (privacy, terms)

Every page is optimized for its target search query.

SEO Architecture

Programmatic but Unique

Each state page has genuinely unique content:

  • State-specific program names and amounts
  • Local utility company programs
  • Climate zone considerations
  • Real dollar amounts (not placeholders)

Schema.org Markup

Every page includes structured data:

  • FAQPage schema for common questions
  • BreadcrumbList for navigation
  • WebApplication schema for the calculator tool

Performance

  • Cloudflare CDN with origin certificate
  • File-based cache eliminates PHP processing on repeat visits
  • Minimal CSS/JS — no frameworks, no jQuery

Content Strategy

The 45 articles cover genuine questions homeowners ask:

  • How much does a heat pump cost in my state?
  • Do I qualify for the HOMES Act rebate?
  • Solar panel rebates vs tax credits — what's the difference?

Each article links to the relevant calculator page, creating natural internal linking.

Monetization

We use Google AdSense with privacy-conscious implementation:

  • Ads only load after explicit cookie consent
  • No tracking without user approval
  • GA4 similarly gated behind consent

Results

  • 111 pages covering all 50 US states
  • Growing organic traffic from long-tail energy rebate queries
  • Users save time finding applicable rebates

Lessons Learned

  1. Government data is messy — program names change, amounts update, documentation quality varies wildly between states
  2. Simple stack scales — file-based caching handles traffic without database connection limits
  3. Trust signals matter — we prominently disclaim non-affiliation with government programs and cite official sources

Try it: Energy Rebate Calculator — Free, no signup, instant results for all 50 US states.

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