ForHosting KIT · Engineering & construction

Feeder voltage regulation calculator

A feeder that reads 240 V at no load and 230 V at full load has a voltage regulation of about 4.3478%, from a 10 V change. Negative results under a leading power factor are shown as valid. Free in your browser.

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Worked example

If you enter

No load voltage: 240
Full load voltage: 230

You get

Voltage drop: 10
Regulation: 0.0434782609
Regulation percent: 4.347826087

Percent voltage regulation is the classical figure of merit for how much a feeder or distribution line sags (or rises) between light load and full load at the receiving end. Designers, utility planners, and students need a single, unit-consistent number: no-load receiving voltage minus full-load receiving voltage, divided by full-load voltage, times one hundred. This feeder voltage regulation calculator accepts those two positive voltages in any consistent unit—volts, kilovolts, or per-unit—and returns the fractional regulation, the percent value, and the absolute voltage change. Leading power-factor cases that raise voltage under load produce a negative percent, which is valid engineering output rather than an error.

What percent voltage regulation means on a feeder

Voltage regulation quantifies how tightly a line holds receiving-end voltage as load changes from zero to the design full-load condition. In power system textbooks and utility standards the receiving-end form is almost universal: take the no-load receiving voltage V_nl, subtract the full-load receiving voltage V_fl, divide by V_fl, and multiply by one hundred to express the result as a percent. A small positive percent means the feeder is stiff—full-load voltage is only slightly below the open-circuit receiving voltage.

A large positive percent means heavy IR and IX drop, long conductors, undersized conductors, or a lagging power factor that pulls the receiving bus down. A negative percent means the receiving voltage rose when load was applied, which commonly appears with capacitive compensation or leading power factor when line capacitance or shunt capacitors overcompensate the inductive drop.

Because both voltages must use the same unit and the same measurement point (receiving end), the calculator does not convert units or transform sending-end readings; you pass the two receiving-end numbers you already measured or simulated. The identity is dimensionless in the ratio, so 240 V and 230 V yield the same percent as 1.0435 pu and 1.0 pu when those pairs are proportional.

Understanding this definition prevents the common mistake of dividing by no-load voltage or by nominal nameplate voltage when the problem statement asks for regulation based on full-load receiving voltage.

Where this regulation figure helps in practice

Distribution design desks use a voltage regulation calculator to screen candidate conductor sizes and feeder lengths before full unbalanced load-flow runs: enter the open-circuit and peak-load receiving voltages from a simple voltage-drop spreadsheet and read percent regulation against utility limits such as five percent or the tighter band in a service-quality code. University power-engineering labs and online homework platforms need a deterministic oracle that matches the textbook receiving-end formula, including negative regulation under leading power factor, so auto-graders never mark a correct capacitive case as wrong.

Failed validation does not consume balance. Keep requests tiny, pin the rounded outputs in tests, and you get reproducible regulation numbers for design memos, LMS plugins, and edge workers without standing up a full power-system study tool.

What you can do with it

Distribution feeder design screening

Convert no-load and full-load receiving voltages from a voltage-drop sheet into percent regulation and compare against utility limits before a full load-flow study.

Power engineering homework and labs

Check textbook %VR problems with a deterministic oracle that accepts negative regulation for leading power-factor and capacitive cases.

FAQ

Which voltage is in the denominator?

Full-load receiving-end voltage V_fl. The classical receiving-end definition divides by V_fl, not by no-load or by nameplate nominal voltage.

How do I calculate voltage regulation from 240 V and 230 V?

Subtract the full-load voltage from the no-load voltage, divide by the full-load voltage and multiply by 100. Here that is 10 divided by 230, about 0.043478, or roughly 4.3478%.

What does a negative voltage regulation mean?

The receiving voltage rose when load was applied, which is common with capacitor compensation or a leading power factor. For example, 0.98 pu at no load and 1.02 pu at full load gives about −3.92%.

Can I enter kilovolts or per-unit values?

Yes, as long as both voltages use the same unit and are measured at the receiving end. The result is a ratio, so proportional pairs in volts or per-unit give the same percentage.

Is a low voltage regulation good?

Yes, a small positive figure means a stiff feeder whose full-load voltage stays close to the no-load value. A large figure points to heavy drop from long or undersized conductors, or to a lagging power factor.

Related tools

For developers — API access

Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.

API endpoint

POSThttps://api.kit.forhosting.com/eng/voltage-regulation

Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.

Call it from your stack

curl -X POST https://api.kit.forhosting.com/eng/voltage-regulation \
  -H "Authorization: Bearer $KIT_KEY" \
  -H "Content-Type: application/json" \
  -d '{"no_load_voltage":240,"full_load_voltage":230}'

const res = await fetch("https://api.kit.forhosting.com/eng/voltage-regulation", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.KIT_KEY}`,
    "Content-Type": "application/json"
  },
  body: JSON.stringify({
    "no_load_voltage": 240,
    "full_load_voltage": 230
  })
});
const { task_id } = await res.json();

import os, requests

res = requests.post(
    "https://api.kit.forhosting.com/eng/voltage-regulation",
    headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
    json={
    "no_load_voltage": 240,
    "full_load_voltage": 230
},
)
task_id = res.json()["task_id"]

<?php
$res = file_get_contents("https://api.kit.forhosting.com/eng/voltage-regulation", false, stream_context_create([
  "http" => [
    "method"  => "POST",
    "header"  => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
    "content" => '{"no_load_voltage":240,"full_load_voltage":230}',
  ],
]));
$task = json_decode($res, true);

body := bytes.NewBufferString(`{"no_load_voltage":240,"full_load_voltage":230}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/eng/voltage-regulation", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)

Example request

{
  "no_load_voltage": 240,
  "full_load_voltage": 230
}

Example response

{
  "task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
  "type": "eng.voltage_regulation",
  "status": "queued",
  "_links": {
    "result": "/tasks/tsk_…/result"
  }
}

The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.

Pricing

Per request$0.002

Published price — no tokens, no invented credits. A failed task is never charged.

Errors

HTTP	Code	Meaning
`401`	`unauthorized`	Missing or invalid API key.
`402`	`insufficient_balance`	Your balance doesn't cover the task price.
`404`	`unknown_type`	That task type doesn't exist.
`429`	`rate_limited`	Too many requests. Use the webhook instead of polling.

Technical notes

Input contract, response fields, and validation rules

Magnitudes above one trillion absolute value are rejected to keep analytic bounds honest. POST a JSON body with two required positive finite numbers: no_load_voltage (aliases v_nl, v0, voltage_no_load, v_receiving_nl, v_no_load) and full_load_voltage (aliases v_fl, vr, voltage_full_load, v_receiving_fl, v_full_load). Each field may arrive as a JSON number or as a numeric string; missing fields, empty strings, non-finite values, zero, and negatives fail with invalid_input naming the field, and those failures are not billed. On success the body echoes both voltages rounded to twelve decimal places for stable cross-runtime goldens, plus voltage_drop equal to V_nl minus V_fl, regulation as the pure fraction (V_nl − V_fl) / V_fl, regulation_percent as that fraction times one hundred, a formula string restating %VR = ((V_nl − V_fl) / V_fl) × 100, method receiving_end_percent_voltage_regulation, and a short human-readable message. Example: no_load_voltage 240 and full_load_voltage 230 yield voltage_drop 10, regulation approximately 0.043478, and regulation_percent approximately 4.3478 percent. Another example: V_nl 0.98 pu and V_fl 1.02 pu (capacitive rise) yields a negative regulation_percent near minus 3.92 percent. Pair the response with your own impedance model if you need to predict V_fl from load current; this endpoint only converts the two measured or computed terminal voltages into the standard regulation metrics and does not solve load flow.

Where a feeder voltage regulation API earns its keep

Energy consultants summarizing field measurements for clients convert logger snapshots at light load and peak load into a single regulation_percent for reports without rebuilding spreadsheet formulas on every engagement.

Integration use cases

Field measurement reports

Turn light-load and peak-load logger readings at the same receiving bus into regulation_percent for client memos and compliance summaries.

Technical questions

How do I calculate feeder percent voltage regulation?

Send positive no_load_voltage (V_nl) and full_load_voltage (V_fl) in the same unit. The API returns %VR = ((V_nl − V_fl) / V_fl) × 100 plus the fractional regulation and voltage drop.

Can voltage regulation be negative?

Yes. When full-load receiving voltage exceeds no-load voltage (voltage rise under load, often leading PF or heavy capacitance), regulation_percent is negative and still a valid success result.

Do the voltages need to be in volts?

No. Use any consistent unit—V, kV, or per-unit—as long as both fields use the same unit and refer to the receiving end.

What does the feeder voltage regulation calculator cost?

The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.

Read the full KIT documentation →

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