Reference

Disclaimer

Where each type of result on this site can deviate from reality, and by roughly how much, area by area.

How accurate are SnapEnergyLab results?

They are as accurate as the inputs and assumptions behind them, and no more. A cost figure using your own tariff and a measured wattage is arithmetic you can rely on. A heat pump saving based on an assumed seasonal performance figure, or a solar yield based on regional irradiance without your roof’s shading, is a scenario — useful for deciding what to investigate, not a prediction of your bill or your generation.

Last updated: 23 August 2026 · Version 1.0

1.What this document covers

1.1

The Terms of Use set out the legal framework for using this site. This disclaimer does something narrower and more practical: it explains, for each calculation area, the specific physical and commercial reasons a real-world outcome can differ from a calculated estimate.

1.2

Every calculator on this site runs in your browser from inputs and defaults you can see and change. Nothing here is a measurement of your home, a quotation, or a performance guarantee.

1.3

Two error sources apply to every area below and are not repeated in each one: the accuracy of the values you enter, and the fact that equipment prices, installation, maintenance, financing, incentives and rebates are deliberately not modelled because credible values for them are local and time-sensitive.

2.Not professional advice

2.1

Nothing on this site is engineering, electrical, financial, tax or legal advice.

2.2

Battery systems, inverters, EV charging equipment, heat pumps and solar arrays involve electrical work, structural load, permitting and safety requirements that must be assessed on site by a qualified professional who is accountable for that assessment.

2.3

Use these calculators to arrive at informed questions, not to replace the answers.

3.Electricity cost and tariffs

3.1

Single-rate simplification. Cost results multiply energy by one rate per kilowatt-hour. Real bills often add standing or fixed charges, time-of-use bands, seasonal rates, demand charges, capacity steps, grid fees and taxes.

3.2

Ranking can flip. Because of that, two options that are close on a flat rate can rank differently on your actual tariff — particularly anything that shifts load into or out of peak hours.

3.3

Prices move. Any rate you enter is a snapshot. Spot-linked and variable contracts can change hourly, and an annual figure derived from today’s rate is a scenario, not a forecast.

3.4

Currency and units. Results are expressed in the currency and units you select; the site does not convert between currencies or apply local rounding and billing conventions.

4.Appliance consumption

4.1

Nameplate is not average use. A nameplate or rated wattage does not necessarily represent an appliance's average real-world power consumption. For most appliances the average is materially lower.

4.2

Duty cycles are assumptions. Refrigerators, freezers, heaters and air conditioners cycle. The site applies a stated typical duty cycle; yours depends on ambient temperature, insulation, door openings, thermostat setpoint, household behaviour and equipment condition. A freezer in a hot garage runs far more than the same freezer in a cool basement.

4.3

Standby and cycles. Standby draw, defrost cycles, compressor start-up surge and inverter-driven modulation are not modelled individually.

4.4

Unit variation. Two products with identical ratings can consume noticeably different amounts of energy, and efficiency generally degrades with age.

4.5

Measurement beats estimation. A plug-in energy meter over a full week will beat any wattage table on this site, and is the recommended step before spending money on a decision.

5.Battery runtime

5.1

Usable is not nameplate. Runtime is calculated from usable energy after depth-of-discharge and round-trip or inverter efficiency, not from the printed capacity. The gap is real and typically substantial.

5.2

Constant-load assumption. Runtime assumes a steady load. Real loads vary, and cycling equipment draws far more during start-up than while running.

5.3

Temperature and age. Available capacity falls in cold conditions and declines over the life of the cells. A battery several years into service will not deliver its first-year runtime.

5.4

Chemistry and discharge rate. High discharge rates reduce deliverable energy, and different chemistries tolerate depth of discharge differently. A single efficiency assumption cannot capture that.

5.5

Conversions. Conversions between mAh, Ah, Wh and kWh depend on the nominal voltage you supply. An incorrect voltage produces a confidently wrong result.

6.Backup sizing

6.1

Energy and power are separate limits. A backup system must supply both enough energy (kWh) for the duration and enough continuous and surge power (W) for the loads at any instant. A system can pass one test and fail the other.

6.2

Surge is not modelled per device. Motors in pumps, compressors and power tools can draw several times their running wattage for a short period. Inverter surge tolerance varies by product and is not evaluated here.

6.3

Your load list is the model. Results reflect the devices and run hours you selected. Outages tend to change behaviour — more lighting, more heating or cooling, more phone and device charging than planned.

6.4

Not a wiring design. Transfer switching, circuit selection, grounding, generator interlocks and code compliance are outside the scope of any figure produced here.

7.Solar yield

7.1

Regional irradiance, not your roof. Yield starts from a regional irradiance value. It does not know your latitude-specific horizon, roof pitch, azimuth, or local microclimate unless you adjust the inputs.

7.2

Shading is the largest unmodelled factor. Trees, chimneys, dormers and neighbouring buildings can reduce output far more than any other variable, and partial shading affects strings disproportionately. The site does not model shading.

7.3

System losses are a single coefficient. Inverter losses, wiring, mismatch, soiling, snow cover and temperature derating are grouped into one system-loss factor rather than modelled individually.

7.4

Year-to-year variability. Annual irradiance varies between years. A single-year figure is a central estimate, not a floor or a guarantee.

7.5

Self-consumption and export. The financial value of generation depends on how much you use on site versus export, and on export tariffs that are local, capped and subject to change.

7.6

Panel count is indicative. Panel-count results assume uniform modules and usable roof area, and ignore setbacks, fire access paths, structural capacity and mounting constraints.

8.EV charging cost and time

8.1

Charging losses. Energy drawn from the wall exceeds energy stored in the battery. Onboard charger, cable and thermal management losses are represented by an assumed efficiency, not by your vehicle’s measured behaviour.

8.2

Charging is not linear. DC fast charging tapers substantially as state of charge rises, so time to 80 percent and time to 100 percent are very different. Simple time results assume an average power that a real session may not sustain.

8.3

Power is limited by the weakest link. Actual power is the minimum of charger output, vehicle acceptance, cable rating, circuit capacity and any site or utility limit — and is further reduced in cold weather or when the battery is hot.

8.4

Public charging pricing. Public networks may price per minute, add session or idle fees, and vary by membership. A per-kWh calculation will not reproduce those bills.

8.5

Range and consumption. Consumption in kWh per 100 km or 100 miles depends on speed, temperature, terrain, tyres, load and climate control. Real-world consumption can be substantially higher than official ratings in cold-weather driving.

9.Heat pump savings

9.1

SCOP is a seasonal average. Savings use a seasonal performance figure, not an instantaneous one. Efficiency falls as outdoor temperature drops, and the coldest days — when heat demand peaks — are the least efficient.

9.2

Emitter and flow temperature. Real performance depends heavily on the required flow temperature. Existing radiators sized for a boiler can push a heat pump well below its rated seasonal figure.

9.3

Backup and defrost. Resistance backup heating, defrost cycles and cycling losses are not modelled separately, and can erode a meaningful share of the calculated saving.

9.4

Fuel comparison. Comparisons against gas, oil or resistance heating depend on the efficiency assumed for the existing system and on the price ratio between electricity and that fuel. Both change, and the ratio decides the outcome more than the heat pump itself.

9.5

Installation quality. Sizing, commissioning and control configuration routinely move real heat pump performance beyond the spread of any assumption on this site.

9.6

Comfort changes behaviour. Households often heat more rooms, for longer, after switching. Consumption then rises even when efficiency improved.

10.Life-safety loads

10.1 Life-safety loads

If medical equipment, sump pumps, well pumps or heating in freezing conditions depend on a backup system, do not size that system from a web calculator alone. Confirm the design with a professional and build in margin — a runtime estimate assumes the equipment behaves as specified, and an outage is exactly when it might not.

11.Contact

11.1

For questions about the estimates, calculations or methodology on this site, contact snapenergylab@gmail.com.