How WattageFit calculates power limits, placement checks and electricity costs

WattageFit separates source-backed values from editable assumptions. Its browser tools are not live electrical measurements, permit approvals, engineering drawings or installation instructions.

USB-C charging model

1. Rated path ceiling: charger power remaining after shared loads, the selected port, cable, device comparison cap and any known protocol ceiling are compared. The lowest rated ceiling is the limiting link.
2. Minimum vs target: a manufacturer-published minimum is not the same thing as a supplied/recommended adapter or fast-charge reference. WattageFit keeps them separate. When a lower minimum is not published, it remains unknown.
3. Protocol: wattage alone is not enough. PPS- or EPR-dependent targets are flagged when the selected charger mode does not confirm that capability. Standard USB Power Delivery/PPS entries are capped at the SPR 100W ceiling; EPR entries can model up to 240W.
4. Manual baselines: a minimum entered by the user is labeled as an entered baseline, not silently promoted to a manufacturer-published cutoff.
5. Heavy load: battery gain or drain depends on live workload draw. WattageFit evaluates a workload threshold only when one is actually supplied rather than inventing one.

Upgrade Impact Lab model

The Upgrade Impact Lab is a counterfactual decision aid, not a product recommendation or charge-time predictor. It starts from the same rated-path result above and changes exactly one input group at a time while holding every other entered value constant.

1. Cable-only scenario: raises only the modeled cable ceiling to at least the selected device target. This is an electrical-ceiling simulation, not a claim that a particular cable product is certified or compatible.
2. Charger + port scenario: raises the total charger budget to at least the device target plus the entered shared load, and raises the selected port ceiling to the target. The cable, device cap, protocol and shared load are otherwise unchanged.
3. Stop-sharing scenario: changes only the entered other-device load to 0W. It does not assume that a real multi-port charger reallocates power dynamically; the manufacturer’s port-allocation table remains authoritative.
4. Highest-impact label: compares the modeled increase in rated path capacity. If a scenario reaches the target but still has a protocol warning, WattageFit says so rather than treating wattage as sufficient proof.

The lab deliberately does not estimate minutes-to-charge from adapter ratings alone. Battery state, charging curves, thermal limits, system load and negotiated profiles can dominate real charging time.

One-Charger Planner model

1. Simultaneous mode: the planning floor is the sum of the selected device target references. Optional headroom is added to the total budget, not used to reduce any device’s required per-port target.
2. One-at-a-time mode: the highest selected device target becomes the total-power floor because only one target device is assumed to charge at a time.
3. Priority mode: Device 1 keeps its full target while each additional selected device receives a 20W planning floor. The result is explicitly a compromise profile, not a promise of fastest charging for every device.
4. Port allocation: headline charger wattage is not treated as proof that the required simultaneous split exists. The result tells the user which per-port combination must be verified in the charger manufacturer’s allocation table.
5. Protocol and cable constraints: PPS-dependent presets are flagged, targets above 100W require EPR, and cable guidance follows the selected device target rather than the charger’s headline total.

The planner rounds the calculated total budget up to the next practical planning class used by the tool. That class is a shopping aid, not a certification or product recommendation.

Current USB-IF context

USB-IF’s document library lists USB Power Delivery Specification Revision 3.2 Version 1.2, dated September 14, 2026. EPR was introduced in PD 3.1 and continues in later specifications. WattageFit therefore describes the capability as EPR rather than presenting “PD 3.1” as the current specification name.

For cables, WattageFit supports 60W, legacy/common 100W and 240W/EPR entries because older e-marked 5A cables remain common while current USB-IF power markings focus on 60W and 240W. A printed marketing wattage is not proof of certification.

Standby generator placement model

1. Manufacturer layer: presets supply only documented starting values; unknown or model-specific requirements stay blank until entered from the exact manual.
2. Multiple openings: up to four wall openings are modeled, and the shortest distance from the generator rectangle to any opening controls the opening check.
3. Property-line layer: there is no nationwide default. The field starts blank until the user supplies a local value.
4. Cross-yard fit: margin = side-yard width − wall clearance − generator depth − local setback. A negative result means the simplified cross-section cannot satisfy all entered transverse constraints.
5. Geometry limit: this is not a survey and does not model overhead clearance, exhaust direction, easements, fuel/electrical routing, flood conditions or every local rule.
6. Privacy/share: ordinary edits stay in browser state; dimensions enter a URL only when a shared URL is opened or the user explicitly copies a share link.

A no-conflict result is not code approval, permit readiness or installation instruction.

Generator primary sources

Regional electricity-cost calculators

For wattage-based estimates, energy is kWh = (W ÷ 1000) × hours × days × quantity × duty-cycle factor. When trustworthy monthly kWh is already known, WattageFit prices that value directly instead of estimating energy from watts.

Appliance wattages and duty-cycle presets are editable examples, not universal specifications. BTU/h is cooling capacity, not electrical input power. Nameplate input power, an energy label or measured kWh should replace a generic example whenever available.

Saudi residential tariff model

The Saudi calculator uses the residential energy tariff published by the Saudi Water and Electricity Regulatory Authority: 18 halala/kWh for monthly consumption from 1 to 6,000 kWh and 30 halala/kWh for consumption above 6,000 kWh. When the user supplies existing household monthly consumption, WattageFit prices the selected appliance as incremental consumption on top of that baseline, so only the portion that actually crosses the 6,000 kWh threshold is priced at the higher tier. Without a household baseline, the tool clearly labels the result as a first-tier estimate rather than pretending to know the user’s bill position.

Kuwait tariff policy

Tariff values are manually reviewed against official Ministry of Electricity, Water and Renewable Energy (MEWRE) sources and stored locally as calculation parameters. WattageFit does not assume that the private-residential 2 fils/kWh rate applies to every account. Official account classification, subsidized-tariff eligibility, fees and the actual bill take priority.

Primary sources

Important limits

WattageFit cannot inspect USB-PD packets, cable e-markers, battery temperature, firmware behavior or a charger’s hidden power-sharing table from a browser. “Available path capacity” is a rated ceiling, not instantaneous device draw.

For electricity, WattageFit cannot know a device’s real duty cycle, meter reading, subsidy status, fees or account classification unless the user supplies the relevant value. The result is an estimate, not a utility bill or a replacement for public-authority instructions.

Core charging sources rechecked September 27, 2026; generator, Saudi and Kuwait tariff sources last reviewed September 22–26, 2026.