Energy Bill HQ
Trust and assumptions

Methodology

Energy Bill HQ is designed to give U.S. homeowners practical comparison estimates, not engineering studies, contractor quotes, or financial advice.

NREL API powered dataPublic U.S. reference inputsEstimate limits stated clearly

Last reviewed

April 15, 2026

Review dates are shown plainly so it is clear when the estimate framework and API integrations were last checked.

How we automate the math

To provide instant, top-of-funnel estimates without requiring complex technical inputs from homeowners, our calculators automatically generate baseline assumptions using official U.S. Government data.

NREL API Integration: When you enter a 5-digit zip code, we securely query public NREL/NLR developer APIs. We use the Utility Rates API for an average residential electricity rate and the PVWatts API for a solar production estimate based on the latitude and longitude returned for that zip code.

Utility-rate limitation: The NREL/NLR Utility Rates API states that its returned rate data is from 2012 and is not complex tariff data. Treat the localized rate as a planning input, then replace it with your current utility bill or quote when you have one.

Dynamic Solar Pricing:We don't use a flat cost-per-watt. Instead, we use a continuous logarithmic decay formula based on an industry baseline of $3.00/watt. This mathematically mimics "economies of scale"—meaning if you have a massive electric bill, the calculator assumes a bulk-discount on your installation cost (with a hard floor of $2.00/watt).

Core default assumptions

  • Solar Offset: We assume a standard 90% bill reduction to account for mandatory grid-connection fees.
  • Home Batteries: Toggling the battery adds a flat $10,000 to model the economics of NEM 3.0 policies.
  • Heat Pumps: We assume a 40% efficiency gain and an $8,000 national average installation cost.
  • Federal Incentives: Current 2026 planning defaults federal solar and heat pump credits to $0. The prior federal windows covered eligible solar property placed in service from 2022 through 2025 and qualifying air-source heat pumps purchased and installed from 2023 through 2025.

What the tools do not model

  • Financing terms, interest rates, and loan dealer fees.
  • Maintenance, degradation, or complex tax liability specifics.
  • Contractor-specific pricing or exact 3D roof shading analysis.
  • Hourly utility tariff nuances (Time of Use rates).

How to use the estimates responsibly

Energy bills, equipment performance, incentives, and installation costs vary wildly by home, climate, utility, and contractor. Treat each automated output as a high-level planning estimate. Use the "Customize advanced assumptions" toggles to overwrite our baseline math with exact numbers from a professional contractor quote.