United States version
How it works
Calculate the connected load and a scheduled-use energy scenario for electric resistance floor heating.
This is the United States planning view, with monetary inputs and outputs in USD. A currency label does not establish that a tax rate, construction price, coverage rule or legal limit has been verified locally. The inputs and limitations below describe the actual scope.
Input query strings and outputs
Use an input name in this page’s URL as ?name=value, and join additional inputs with &. Portable shared links may instead use the compact ?ac= state parameter.
Input query strings
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?unitSystem=Measurement systemChoice · Optional · Default: imperial · Accepted values: imperial, metric
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?area=Heated floor areaNumber · Required · Default: 129.166925000517
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?wattsPerSqm=Installed electric output, W/m²Number · Required · Default: 150
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?hours=Heating hours per dayNumber · Required · Default: 4
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?days=Heating days per yearNumber · Required · Default: 180
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?dutyCycle=Average on-time within scheduled hoursPercentage · Required · Default: 50
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?electricityRate=Electricity price per kWhMoney · Required · Default: 0.2
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?unitRate=Material price per area unitMoney · Required · Default: 0
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?laborCost=Total labor allowanceMoney · Required · Default: 0
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?deliveryCost=Delivery allowanceMoney · Required · Default: 0
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?otherCost=Other fixed costsMoney · Required · Default: 0
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?costMultiplier=Material/labor multiplierNumber · Required · Default: 1
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?spreadPercent=Low/high sensitivity around the entered totalPercentage · Required · Default: 15
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?taxRate=Explicit tax allowancePercentage · Required · Default: 0
Outputs
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installedKwInstalled electrical load, kWNumber
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annualKwhModeled annual electricity, kWhNumber
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annualEnergyCostAnnual energy costCurrency · Currency: USD
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materialCostMaterial costCurrency · Currency: USD
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laborCostLabor allowanceCurrency · Currency: USD
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deliveryCostDelivery allowanceCurrency · Currency: USD
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otherCostOther specified costsCurrency · Currency: USD
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taxEntered tax allowanceCurrency · Currency: USD
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lowLow cost scenarioCurrency · Currency: USD
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midMiddle cost scenarioCurrency · Primary output · Currency: USD
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highHigh cost scenarioCurrency · Currency: USD
Formula
annual kWh = area × watts per square metre ÷ 1,000 × hours × days × duty fraction.
Calculations retain numeric precision internally. Displayed values are rounded for readability. Quantities that must be purchased as whole units are rounded up only where the formula explicitly requires it.
Read the inputs before calculating
- Heated floor area: Enter the quantity described by the label. The measurement selector converts this physical quantity; it does not change the underlying scenario.
- Installed electric output, W/m²: Enter the quantity described by the label.
- Heating hours per day: Enter the quantity described by the label.
- Heating days per year: Enter the quantity described by the label.
- Average on-time within scheduled hours: Enter the quantity described by the label.
- Electricity price per kWh: Enter the quantity described by the label.
- Material price per area unit: Zero means unpriced, not free. Enter a current, scoped supplier quote. This is a price per displayed unit, so the price converts inversely to the physical quantity.
- Total labor allowance: Enter the quantity described by the label.
- Delivery allowance: Enter the quantity described by the label.
- Other fixed costs: Enter the quantity described by the label.
- Material/labor multiplier: Use a verified regional index only when supplied. 1 is an unadjusted scenario, not a researched index.
- Low/high sensitivity around the entered total: Enter the quantity described by the label.
- Explicit tax allowance: Enter the quantity described by the label.
Reproducible worked example
The following is a fictional arithmetic example, not a local quote, a verified claimant or a market forecast. Its values are included so the formula can be checked. The form does not automatically confirm any verification checkbox.
| Input | Example value |
|---|---|
| Heated floor area (ft²) | 129.1669 |
| Installed electric output, W/m² | 150 |
| Heating hours per day | 4 |
| Heating days per year | 180 |
| Average on-time within scheduled hours | 50 |
| Electricity price per kWh | 0.2 |
| Material price per area unit (/ft²) | 0 |
| Total labor allowance | 0 |
| Delivery allowance | 0 |
| Other fixed costs | 0 |
| Material/labor multiplier | 1 |
| Low/high sensitivity around the entered total | 15 |
| Explicit tax allowance | 0 |
| Output | Calculated result |
|---|---|
| Installed electrical load, kW | 1.8 |
| Modeled annual electricity, kWh | 648 |
| Annual energy cost | USD 129.6 |
| Material cost | USD 0 |
| Labor allowance | USD 0 |
| Delivery allowance | USD 0 |
| Other specified costs | USD 0 |
| Entered tax allowance | USD 0 |
| Low cost scenario | USD 0 |
| Middle cost scenario | USD 0 |
| High cost scenario | USD 0 |
Interpreting a changed assumption
Start with one complete scenario and change only one input when diagnosing a difference. Recheck units, the period of every rate, whether an amount is recurring or one-off, and whether a cost is already included elsewhere. A larger calculated benefit is not evidence that an assumption is more likely to occur.
Limitations
- Material is unpriced. A zero material price is not evidence that the material is free.
- Prices and the tax allowance are user-entered planning assumptions, not a verified local quote. Low/high outputs are sensitivity scenarios, not market confidence limits.
- The multiplier applies only to material and labor; delivery and fixed costs are not multiplied.
- This model is for electric resistance mats/cables, not a hydronic floor or a room heat-loss design. Manufacturer output is entered in W/m² in both unit systems.
Frequently asked questions
What does this Electric Radiant Floor result represent?
Calculate the connected load and a scheduled-use energy scenario for electric resistance floor heating. It applies the displayed formula to your inputs; it does not infer omitted facts.
Are the starting amounts verified United States prices or legal rules?
No. Numeric defaults are illustrative unless an input or dated reference explicitly identifies a researched component. Currency is USD; local quotes, eligibility and unsupported rules must be entered and verified separately.
What must I check before relying on the result?
Check the input units, supplier or authority evidence, the stated model exclusions and the period used for costs. This arithmetic does not supply missing site-specific design or local legal rules.
Can I compare or share different assumptions?
Change one assumption at a time and use the browser-local project or share controls. A shared URL contains the encoded input values; do not include information you do not wish to disclose.
Sources and reference scope
- DOE energy-use arithmetic — retrieved 2026-09-24. Energy consumption versus power; not a local tariff or an approval of this implementation.
- PVWatts: site-specific solar estimation — retrieved 2026-09-24. External site-yield model. AskCalculators uses your entered yield; it does not call or reproduce PVWatts.
- DOE insulation overview — retrieved 2026-09-24. Insulation and thermal resistance concepts; not structural or code approval.
These references support only their stated scope. They are not evidence that every local rule or price needed by the master expansion has been loaded.