CONSIDERED SOLAR TOOLKIT

Solar Annual Generation Estimator

Estimate how much electricity your solar could generate through the year, including roof direction, real-world system losses and the AC limit of your inverter.

✓ Multiple roof faces and exact compass bearings✓ Compare solar generation with your household electricity use✓ Precise location is not stored by this test tool

v1.1.6Updated 1 September 2026Live on Considered

Start estimating ↓

Need help finding your figures?Location, array size, compass direction, roof pitch and annual electricity use

Array size

Use the installed or proposed DC array size in kWp. For example, ten 440 W panels = 4.4 kWp.

Direction / bearing

Choose a compass direction, or enter an exact bearing from a phone compass: 0° north, 90° east, 180° south and 270° west.

Roof pitch

This is the angle of the panels above horizontal. Installer documents may include it; otherwise a reasonable estimate is fine for exploring scenarios.

Annual electricity use

Use the last 12 months from your supplier app, bill or annual statement. The free comparison spreads this evenly across the year, so it is indicative only.

YOUR SYSTEM

Build the scenario

1. Location

UK postcode Quick and easy; this resolves to an approximate local coordinate.

Privacy first

Precise coordinates are used for the calculation but are not stored by Considered in this test version. Browser location is requested only when you choose it.

LatitudeLongitude

Location not resolved yet.

2. Solar arrays

How much shading does the site experience? Use this as a simple overall allowance for trees, buildings or other persistent shade.

3. Inverter & system

Inverter AC output Maximum continuous AC output of the solar inverter.kW Typical system losses Wiring, mismatch, dirt, availability and other real-world losses. Most people can leave 14%.%

Panel kWp and inverter kW are different. Oversizing an array is normal, but output above the inverter limit can be clipped.

4. Your electricity use

Current annual electricity consumption Used to draw an average monthly consumption line on the graph.kWh/year Installer's annual generation estimate Optional. Useful if you want to sense-check a quote.kWh/year Known actual annual generation optionalIf you have a full year's generation data, compare it with both estimates.kWh/year

YOUR ESTIMATE

Estimated solar generation

Your results will appear here.

Set your location and arrays, then calculate. Each roof face will get its own graph series so you can see exactly what it contributes.

CONSIDERED BLENDED ESTIMATE——

All selected arrays

ARRAY CAPACITY—

INVERTER—

DC:AC RATIO—

EST. CLIPPING—

INDEPENDENT MODEL CHECK—

—

Considered combines three perspectives so you get one practical planning figure rather than being asked to choose between competing estimates.

NASA POWER model— PVGIS model— UK MCS-style benchmark—

Blend: NASA 35% · PVGIS 45% · MCS-style 20%. Nearby trees and buildings are not automatically known to these data sources.

Monthly generation

Each array is stacked into the usable total. Turn arrays on or off to recalculate the blended estimate instantly. The monthly shape combines NASA and PVGIS profiles, with the MCS-style annual reference distributed across that profile. If inverter clipping is material, a soft red cap shows the NASA-modelled energy that could not pass through the inverter.

ARRAY CONTRIBUTION

What each part of the system adds

Array	Size	Bearing	Estimated generation	Contribution

How to interpret these estimates

Considered blended estimate: the headline is a weighted planning figure combining the NASA POWER-based model (35%), PVGIS (45%) and the UK MCS-style benchmark (20%). We round the result because the source models do not justify false precision.

NASA POWER: supplies long-term location-specific solar and temperature data. Considered applies orientation, pitch, mounting temperature, entered system losses and inverter constraints.

PVGIS: provides an independent European Commission/JRC photovoltaic generation calculation for the same array size, direction, pitch, mounting and loss assumptions. PVGIS terrain horizon data can help with distant terrain, but nearby trees and buildings are not automatically known.

UK MCS-style benchmark: remains a separate standardised UK planning reference useful when comparing installer paperwork. The current embedded MCS engine is still a prototype reference rather than an official current MCS Kk implementation.

If the models differ: the range is useful information. A wider spread means local assumptions matter more. Nearby shading can reduce real output below all three generic models, which is why the result is a planning estimate rather than a promise.

Household consumption: your annual consumption is divided evenly across 12 months for the free comparison. Real electricity demand varies by season and, crucially, by time of day. A month where generation exceeds this line does not mean you will avoid importing electricity.

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