Trust & methodology

How VoltTally builds and checks its tools

Q: How can I report an incorrect or outdated assumption?

Email carproange@gmail.com with the page URL, the input or value in question, the result you expected, and a current primary source. Reproducible safety and factual corrections take priority over adding new pages.

VoltTally publishes planning calculators, not permits, bids, utility approvals, or electrical designs. We keep the arithmetic inspectable, identify material assumptions, and route safety- or code-sensitive decisions to a licensed professional and the authority having jurisdiction.

Content and source links last reviewed 2026-07-27.

Editorial and calculation standards

Calculations and explanations stay separate

Calculator results come from explicit formulas, versioned data, and pure calculation engines. Page copy explains how to interpret the result; it does not replace or silently alter the calculation.

Assumptions stay visible

Inputs, source dates, default rates, market ranges, and important omissions are shown near the tool so a reader can decide whether the estimate fits the real project.

Safety limits stay prominent

Electrical and HVAC results are planning estimates. Equipment labels, installation method, temperature, load calculations, permits, adopted code, and the authority having jurisdiction can change the final requirement.

Ordinary inputs stay in the browser

The public calculators do not require an account. Ordinary values entered into a calculator are evaluated locally in the browser rather than submitted to a VoltTally application server.

Source hierarchy and freshness

For safety rules and public programs, we prefer standards publishers, government agencies, utilities, national laboratories, adopted-code authorities, and equipment instructions. Rule-backed tools carry a data or rules date and, where material, a source-check date. Market-cost ranges are labelled as indicative and dated. A source URL does not turn a simplified planning model into a code-compliance calculation.

NFPA 70: National Electrical Code — Official NFPA code-development and current-edition access page.
U.S. Department of Energy: estimating appliance energy use — Explains the watts × hours ÷ 1,000 method and why measured use is preferable.
U.S. EIA: residential electricity prices by state — Monthly residential price benchmarks; your own utility bill remains the accurate input.
ENERGY STAR: ductless heating and cooling — System fit, placement, cold-climate considerations, and Manual J sizing guidance.
ENERGY STAR: air-source heat pumps — Efficiency, equipment selection, and professional sizing guidance for ducted systems.
IRS: current home-energy credit expirations — Current IRS summary stating that section 25C is unavailable after December 31, 2025.
U.S. Department of Energy: Affordable and Equitable Residential Electrification Under Electrical Panel and Service Constraints — panel-load source checked 2026-07-14.
U.S. Department of Energy: Electric Vehicle Supply Equipment Infrastructure — Federal Fleet Training — panel-load source checked 2026-07-14.
Pacific Gas and Electric Company: How to switch to electric appliances without an electrical panel upgrade — panel-load source checked 2026-07-14.

Tool-by-tool source basis and limits

Tool Source and method basis Important limits

Voltage drop NEC Chapter 9 conductor-resistance data and standard single- or three-phase voltage-drop formulas. Does not perform ampacity, conductor-count or temperature derating, conduit fill, power-factor, or local-code checks.

Wire size NEC 310.16 ampacity data, 240.4(D) small-conductor limits, and Chapter 9 resistance data. The final conductor depends on terminal ratings, continuous-load treatment, installation method, ambient conditions, equipment instructions, and the AHJ.

Panel-load precheck User-entered existing demand plus proposed simultaneous EV and heat-pump loads, with NEC continuous-load context. This is arithmetic triage, not an NEC dwelling load calculation, service inspection, utility approval, or permission to install equipment.

EV charger cost Dated indicative ranges for hardware, circuit routing, labor, permits, and possible panel work. Actual bids vary by routing, trenching, panel capacity, service capacity, labor market, permits, utility rules, and equipment choice.

Electricity cost Watts × hours ÷ 1,000, user-entered or EIA benchmark electricity prices, and clearly labelled appliance presets. Real use depends on measured draw, duty cycle, thermostat settings, weather, equipment condition, and the utility tariff.

Heat-pump cost Dated indicative installed-cost ranges, system configuration inputs, ENERGY STAR sizing guidance, and current IRS credit status. A Manual J load calculation, climate, duct condition, equipment tier, electrical scope, contractor bids, and local incentives can materially change the result.

Testing and corrections

Pure calculation engines have automated boundary and regression tests. Before release, the static build is checked for expected routes, canonical URLs, robots directives, sitemap membership, and required public files. If an official source conflicts with a model, the factual correction takes priority over adding pages.

Corrections policy

Send corrections to [email protected]. Include the page URL, the input or statement in question, a reproducible example, and a current primary source when possible. We do not invent professional review or credentials; pages identify their actual source basis and limits.

FAQ

Can VoltTally replace a licensed electrician or HVAC contractor?

No. VoltTally provides planning estimates and comparison tools. Confirm code-sensitive, permit-sensitive, equipment-sizing, and safety decisions with qualified professionals, current equipment instructions, and the local authority having jurisdiction.

How can I report an incorrect or outdated assumption?

Email [email protected] with the page URL, the input or value in question, the result you expected, and a current primary source. Reproducible safety and factual corrections take priority over adding new pages.