Self Consumption Calculations

Our software provides three ways to calculate how much of your solar PV generation is used on-site (self-consumption) and how much of your annual demand can be covered by solar energy.

The methods are designed to be transparent and aligned with MCS Guidance Document MGD 003, where applicable.

1. Archetype Method (Within MCS Lookup Table Range)

When your PV generation and annual electricity demand are within the official MCS lookup table range (0–6,000 kWh/year), our software uses MCS-approved data from MGD 003.

You select one of the archetypes that best matches your household pattern:

Home all day – higher daytime usage.

In half day – moderate daytime usage.

Out all day – lower daytime usage.

The results returned are based directly on official MCS values for self-consumption.

You must use the MCS look-up table when the PV system falls within these defined parameters:

Parameter Limits (as of current MCS guidance)
Annual Generation from Solar PV System ≥ 0 kWh and ≤ 5999 kWh/year

Customer’s Annual Consumption ≥1500 kWh and ≤ 5999 kWh/year

Battery Energy Storage Usable Capacity ≥1.1 kWh and ≤ 15.1 kWh

2. Archetype Method (Beyond MCS Lookup Table Range)

If your PV system’s generation is above 6,000 kWh/year or otherwise outside the official MGD 003 table values, the software will still use the selected archetype but applies a conservative extrapolation method.

This approach is informed by the patterns in MGD 003 (e.g., how self-consumption changes as generation increases) but is extended to accommodate larger systems.

We take into account:

Total PV generation,

Annual household demand (you can never self-consume more than you use),

Daytime occupancy patterns (via your chosen archetype).

Important Note: These extrapolated values are clearly marked as estimates beyond the official MCS lookup tables. This is done to provide you with a realistic and useful figure while staying consistent with MCS principles.

3. Custom Percentage Installer Calculation Method

If you have detailed knowledge of your own consumption patterns—for example, if you have data from a smart meter, or you know when high-demand appliances are used—you can choose to set your own expected self-consumption percentage.

This allows you to fine-tune the calculation to reflect specific behaviours (e.g., electric vehicle charging during the day, use of immersion heaters, or other high loads).

When you select this option, the software uses your chosen percentages instead of MCS or extrapolated data.

You are ONLY ALLOWED to use the installer calculation method if:

The system size or annual consumption falls outside the defined parameters.

OR

The system involves non-standard components or site-specific complexities that require detailed modelling.

Which Method Should I Choose?

Most users should select the archetype method (Option 1) as this gives a reliable estimate based on MCS-approved data.

If your PV generation is larger than 6,000 kWh/year, the extrapolated archetype method (Option 2) will be applied automatically.

If you know your system’s behaviour and have reliable data, you can select custom percentage mode (Option 3) for a tailored calculation.

Transparency and Compliance

MGD 003 values are always used where available (0–6,000 kWh/year) to ensure compliance with MCS standards.

Extrapolated calculations are clearly identified as being beyond official MCS table values, but they remain grounded in the same principles.

Custom percentages give flexibility but are entirely Paperclip user-driven, with responsibility for accuracy resting with the user.