Methodology
How our calculators work, where the numbers come from, and what we do — and don't — account for.
Last updated: June 13, 2026
Our five-part standard
Every calculator on KilowattKit must meet all five criteria before it is published:
Visible formula
The exact formula used is shown on the page in plain text. We do not use black-box calculations.
Named assumptions
Every input that uses a default is identified and explained. We tell you what we assumed and why.
Cited sources
Every numerical default links to the official source it came from, with a last-verified date.
Worked example
Each calculator shows a worked example with realistic inputs so you can verify the output manually.
Scope statement
We explicitly state what each calculator does NOT include, so results are never mistaken for a complete picture.
Data sources and update schedule
Rate defaults (electricity, gas) are sourced exclusively from official government and regulatory bodies:
| Country | Electricity source | Gas source | Updated |
|---|---|---|---|
| 🇺🇸 US | EIA Electric Power Monthly | EIA Natural Gas Prices | Quarterly |
| 🇬🇧 UK | Ofgem Energy Data Portal | Ofgem | Quarterly |
| 🇨🇦 CA | Natural Resources Canada | Canada Energy Regulator | Quarterly |
| 🇦🇺 AU | Australian Energy Regulator | AER | Quarterly |
Appliance wattages and equipment efficiency figures are sourced from ENERGY STAR, DOE, and EPA fueleconomy.gov and reviewed annually.
What our calculators do not account for
To keep our tools accessible and fast, they use simplified models. The following are not included unless explicitly noted on a specific calculator:
- Tiered or time-of-use electricity pricing
- Demand charges on commercial tariffs
- Regional rebates, tax credits, or utility incentive programmes
- Equipment installation costs, maintenance, or depreciation
- Seasonal or weather variability in energy use
- Behavioural change effects over time
- Inflation in energy prices over future payback periods
How each calculator is researched
KilowattKit was built by a non-engineer who read the primary sources — not an industry insider, not a software company. The research process for every calculator follows the same six steps:
Step 1
Identify the official primary source
For every country and energy type, we go straight to the top-level regulator: EIA for the US, Ofgem for the UK, Natural Resources Canada for Canada, the Australian Energy Regulator for Australia. We do not use secondary sources — press articles, blog posts, or industry estimates — as input data.
Step 2
Extract the specific figure and record where it came from
We note the exact document, table, and date for every default value. If a source updates its numbers, we can trace back to the original figure and see exactly what changed. These citations appear in the "Sources" block on every calculator page.
Step 3
Cross-check against at least one independent official source
Wherever possible, we verify a figure against a second official source. For US electricity rates, for example, we compare the EIA Electric Power Monthly table against state-level utility commission filings. If figures disagree, we use the more conservative (higher-cost, lower-savings) estimate and note the discrepancy.
Step 4
Build the formula from first principles
We write out the formula in plain arithmetic before any code is written — for example: kWh used × rate per kWh × days = cost. The formula is then tested with worked examples (published on the page) and checked against published estimates from the same official sources.
Step 5
State every assumption explicitly
Any input that uses a default — average rate, typical appliance wattage, standard usage hours — is identified in the "How it's calculated" section. Users who know their own numbers can override every default.
Step 6
Set a review date and update quarterly
Electricity rates and government grant values change. Every calculator carries a "Last verified" date. We review rate defaults quarterly and update grant pages as soon as programme changes are announced.
Corrections policy
If an error is reported or identified in a formula, data default, or source citation, we will: (1) investigate within 48 hours, (2) correct confirmed errors within 7 business days, (3) update the "Last verified" date on the affected page, and (4) log the correction on our updates page.
To report an error: [email protected]