Solar and battery terms, in plain English
Quick answer: This glossary defines the solar and battery terms you will meet when retrofitting a battery in Scotland: AC-coupled, DC-coupled, DNO, G98, G99, hybrid inverter, kWp, kWh, MCS, MIS 3002, SEG, string inverter, VAT and more — in plain English without jargon.
The terms you will meet when retrofitting a battery in Scotland — defined simply, without jargon. Use this glossary alongside the compatibility checker and FAQ to understand your assessment.
Technical terms
- AC-coupled: A battery with its own built-in inverter, connecting on the AC side of your wiring. The Tesla Powerwall 3 is AC-coupled.
- DC-coupled: A battery connecting directly to a hybrid inverter, with DC power flowing from solar panels to battery without an AC conversion step. More efficient but requires a compatible hybrid inverter.
- DNO: District Network Operator. The company that owns and operates the electricity network in your area. SP Energy Networks covers central and southern Scotland; SSEN covers the north, Highlands and Islands.
- G98: The DNO notification standard for small-scale generators (up to 3.68kW per phase). Your installer notifies the DNO within 28 days of installation — no prior approval needed.
- G99: The DNO approval standard for larger generators (above 3.68kW per phase). Requires prior approval from your DNO before installation begins. Typically takes 4 to 8 weeks.
- Hybrid inverter: An inverter that manages both solar panels and a battery in one unit, allowing DC power to flow from panels to battery without a separate conversion step.
- kWp: Kilowatt peak. The rated capacity of a solar panel system under standard test conditions. A 4kWp system produces 4kW under ideal conditions.
- kWh: Kilowatt hour. A unit of energy. One kWh means using 1,000 watts for one hour. Your electricity bill is measured in kWh.
- MCS: Microgeneration Certification Scheme. The quality assurance scheme for renewable installations in the UK. We install through MCS-certified partners.
- MIS 3002: The MCS standard for calculating solar PV generation estimates. All yield figures on this site are given as ranges per MCS MIS 3002.
- SEG: Smart Export Guarantee. A government scheme requiring electricity suppliers to pay you for excess renewable energy you export to the grid. Rates vary by supplier.
- String inverter: A traditional solar inverter that converts DC power from a string of solar panels to AC power for your home. Common in systems installed before 2018.
- VAT: Value Added Tax. Solar panels, battery storage and heat pumps qualify for 0% VAT until 31 March 2027 in the UK.
Scheme terms
- EPC: Energy Performance Certificate. A rating of your home's energy efficiency from A (best) to G (worst). Required when selling or renting a property.
- Feed-in tariff (FIT): A government scheme that paid homeowners for renewable electricity generation. Closed to new applicants in March 2019, but existing recipients continue to receive payments until their tariff end date. A battery does not affect FIT payments because FIT is based on deemed generation, not actual export.
- Time-of-use tariff: An electricity tariff where the price per kWh varies by time of day. Examples include Octopus Agile, Octopus Go, and similar tariffs. A battery lets you charge off-peak and discharge at peak rates, maximising the value of stored energy.
- Off-peak charging: Using cheaper overnight electricity to charge your battery, then discharging that stored energy during the day when rates are higher. This is how a battery saves money even in winter when solar generation is low.
- Self-consumption: Using the electricity your solar panels generate directly in your home, rather than exporting it to the grid. A battery increases self-consumption by storing surplus generation for use when the panels are not producing.
- Three-phase supply: A type of electrical connection common in larger properties and commercial buildings. The 3.68kW G99 threshold applies per phase, so a three-phase connection can accommodate a larger battery without prior approval. Most Scottish homes are single-phase.
Frequently asked questions
What does DNO mean?
DNO stands for Distribution Network Operator — the company that manages the electricity grid in your area. In Scotland, SP Energy Networks covers central and southern Scotland, and SSEN covers the north, Highlands and Islands.
What is the difference between G98 and G99?
G98 is a notification for small battery systems under 3.68kW, sent to your DNO within 28 days of installation. G99 is prior approval required for larger systems over 3.68kW before installation can proceed.
What does MCS mean?
MCS is the Microgeneration Certification Scheme — a quality assurance scheme for small-scale renewable installations. We install through MCS-certified partners, ensuring installations meet recognised standards.
Related guides
Last updated: 28 October 2026
Reviewed by the Scottish Energy Efficiency team.
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