Methodology

General estimating principles

1. Inputs and stored data produce a result. The calculation functions receive their data explicitly. Interactive calculations do not obtain live contractor bids.
2. Published data and assumptions have different evidence. Energy datasets can support an energy price without validating construction rates beside it. Installed-price bands, regional factors and optional-work allowances remain model inputs unless their exact provenance is documented.
3. Comparable inputs matter. Worked examples and interactive tools must use the same size, scope and settings before their results can be compared. Shared components now align pool state baselines and the reviewed heating tables; other text-only guide ranges can have different scope and require separate review.
4. A range is not a confidence interval. Low and high estimates come from configured rate bands or a model uncertainty allowance. They are not a statistical guarantee that a future quote will fall inside the range.
5. Regional factors are not measured wages. Their point of application differs by engine. A state factor does not capture every city’s labor market, site access or contractor.

See data provenance for the remaining source-to-value gaps. We do not invent local samples, contractor quotes or expert endorsements to fill those gaps.

Solar methodology

1. Usage and sizing. A bill-based estimate converts spending to electricity use using the selected energy price. Target offset, sun-resource assumptions and performance ratio lead to a system size rounded to whole panels.
2. Production. Free estimates use the stored solar-resource and production assumptions. Roof analysis can use modeled geometry and output from the Google Solar API. Neither path is a measurement of future generation.
3. Gross price. The cost model uses system watts, a configured installed price per watt, roof adjustments, an optional battery and a fixed soft-cost allowance. Local quoted scope can differ.
4. Finance and incentives. Model credit, loan and lease/PPA inputs are shown below. They are not lender offers or confirmation of eligibility. Verify applicable dates and conditions through the policy sources before making a financial commitment.
5. Savings and payback. Modeled production, export treatment, degradation and assumed energy-price escalation drive the savings projection. Changing those assumptions changes payback; this is not an investment-return guarantee.

Estimate for pre-qualification, not a final engineering design.

Pool methodology

The free construction calculator is an additive budget model. Its reference is distinct from any detailed paid-report scope; a drawn outline or satellite image is not a site survey.

1. Surface area. Length × width supplies the rectangular footprint; supplied polygon area and perimeter can be used by the calculation interface where available.
2. Base shell. Fixed base for the pool type + area × variable square-foot rate × regional factor × (average depth / reference depth). The regional factor applies to this variable portion, not the fixed base or every feature.
3. Sitework. The excavation adjustment multiplies the base shell. It is a simplified scenario, not a separate soil investigation or measured excavation quote.
4. Features. Selected heating, decking, saltwater, automation, lighting, spa, water features, cover and fencing add the configured allowances. An unselected feature is excluded.
5. Range. The reference construction result uses a modeled ±15% band around the calculated total. That is not a survey-derived confidence interval.

Pool state examples and their calculators start from a 20 × 20 ft, 5 ft deep gunite pool, flat excavation and no add-ons. The national tool keeps its separate 32 × 16 ft default. Compare like-for-like settings rather than treating those initial outputs as contradictory prices for one project.

Estimate for pre-qualification, not a quote; price varies by contractor, location, and season.

Pool heating assumptions

Heating installation allowances are fixed by type. Operating allowances scale by surface area and energy price; heated months are capped by the model’s regional season. Natural gas and electricity are scaled separately. The tool does not calculate propane prices, heater capacity or hours to a target temperature.

The maintenance calculator uses a separate heating allowance. Remove that allowance before adding a standalone heating estimate, or the same cost can be counted twice.

Fence methodology

1. Run and material. Entered linear feet, chosen material and height determine the base run at stored installed rates.
2. Site assumptions. Terrain, soil and regional adjustments affect the estimate. Stored depth and spacing assumptions drive post and concrete quantities; they are not a survey of your fence line or approval of the installation.
3. Additional work. Selected gates, removal and permit allowances add scope. Project-size adjustments can alter the effective per-foot cost.

Verify boundaries, actual ground conditions, utilities and local requirements separately. A configured frost-depth or permit value is not an official determination for an address.

Ballpark estimate for planning, not a bid. Post counts assume a rectangular run; a contractor will confirm corners, gates, and local code. Get 3 local quotes before signing.

Driveway methodology

1. Area and material. Square footage is priced using the configured installed rate for asphalt, concrete, pavers or gravel.
2. Section and site. Depth changes the material portion relative to its reference section; load, slope/drainage, access and regional factors adjust the budget.
3. Extras and takeoff. Selected tear-out, disposal and permit allowances are shown separately. Material quantities are planning takeoffs, not an engineered pavement specification.

Confirm drainage, subgrade, public-right-of-way work and any curb-cut scope before comparing bids.

Ballpark estimate for planning, not a bid. Assumes a rectangular pad on a standard base; soft soils, drainage work, and curb-cut/apron rules are the usual extras. Get 3 local quotes before signing.

Siding methodology

1. Gross wall area. Footprint perimeter × wall height, plus gable triangles estimated from the assumed aspect ratio, roof style and pitch.
2. Net and order area. Subtract the selected share of window and door areas, then apply the waste factor. One siding square is 100 square feet; it is not indoor floor area.
3. Installed line. Order area in square feet × the configured installed dollars per square foot. Do not multiply a count of squares by a square-foot rate without converting units.
4. Removal and permit. Optional tear-off uses net area and the removal rate. A generic permit allowance is added; it is not the municipality’s actual fee.
5. Subtotal adjustments. Complexity, story count, small-project and regional factors multiply the assembled subtotal. The regional factor is not an independently measured hourly wage.

Starter strip, housewrap, corner posts and material quantities are takeoff outputs. Hidden repairs and hazardous-material work are outside the standard removal allowance. The Maine planning page separates those questions from the modeled price comparison.

Ballpark estimate for planning, not a bid. Wall area is estimated from your footprint — a contractor will measure each wall. Excludes hidden rot, sheathing replacement, and structural repairs found at tear-off. Get 3 local quotes before signing.

HVAC methodology

1. Two screening loads. Entered floor area and stored climate factors provide separate cooling and heating starting points.
2. Envelope adjustments. Configured age, insulation, window, ceiling-height and sun-exposure factors adjust the screening model. They do not replace room-by-room measurements.
3. Equipment and scope. Modeled capacity and selected system type lead to equipment allowances. Ductwork, removal, electrical work and permits add or change scope; regional factors adjust the budget.
4. Not a Manual J. A qualified contractor must perform the appropriate load calculation and equipment selection before installation. A cost-estimator output is not a compliant HVAC design.

Ballpark estimate for planning, not a bid. Sizing is a screening calculation from your square footage and climate — a contractor must run an ACCA Manual J load calculation before install. Excludes gas-line work, flue relining, asbestos abatement, and structural chases for new ducts. Get 3 local quotes before signing.

Energy-price snapshots

Stored energy data currently extends through April 2026. Refresh scripts obtain residential electricity and natural-gas data and construct trailing averages. A state average is not the same as a household’s utility tariff; fixed charges, time-of-use rates and service conditions can differ.

The typed data layer supplies these values to the relevant calculations. Missing local values can fall back to configured national/default values. Roof-report tariff lookups are a separate integration, not proof that every free estimate uses a property-specific bill.

Data freshness and review

A refresh script or planned cadence does not prove that data was refreshed. Dataset dates and editorial review dates describe different changes. An article wording update must not be presented as a new contractor survey or a current price observation.

Known limitations

These estimates cannot inspect hidden damage, soil, drainage, utilities, roof condition or access. They do not establish permit approval, incentive eligibility or insurance coverage. A selected default is a model assumption, not a verified characteristic of the user’s property.

State comparisons and CSV reports are modeled scenarios. Until a complete source-to-value record is available, construction rates and regional factors must not be described as representative local bid statistics. Obtain comparable written quotes and the appropriate professional assessment before committing to work.