Solar & renewables glossary

20 key terms explained

Bookmark this page — you can come back whenever you encounter an unfamiliar term in your quote or grant paperwork.

01MCS (Microgeneration Certification Scheme)

An industry-led quality assurance scheme for renewable energy installations. MCS certification is required for your installer to register your system on the MCS Installation Database, which in turn is required to claim the Smart Export Guarantee and most grants. Installation is carried out by our MCS-registered partner, Home Heating Services (Scotland) Ltd.

02SEG (Smart Export Guarantee)

A UK government scheme requiring licensed energy suppliers to offer a tariff for small-scale electricity exported to the grid. You must have an MCS-certified installation and a smart meter or approved export meter. Rates vary by supplier — we help you find the best deal.

03DNO (Distribution Network Operator)

The company that owns and operates the local electricity distribution network. In Scotland, this is either SPEN (SP Energy Networks) covering the Central Belt and south, or SSEN (Scottish & Southern Electricity Networks) covering the Highlands and north-east. You must notify your DNO before connecting a generator to the grid.

04kWp (Kilowatt Peak)

The peak power output of a solar panel or array under standard test conditions (STC: 1,000 W/m² irradiance, 25°C cell temperature). A typical domestic system in Scotland is 4–8 kWp. Real-world output varies with irradiance, temperature, shading, and orientation.

05EPC (Energy Performance Certificate)

A rating of a property's energy efficiency from A (most efficient) to G (least efficient). Required for selling or renting a property. Installing solar panels, insulation, or a heat pump can improve your EPC rating. An EPC is also needed for some grant applications.

06G98

The Engineering Recommendation that covers the connection of small generators (up to 16A per phase, typically up to 3.68 kW single-phase or 11.04 kW three-phase) to the distribution network. Most domestic solar installations fall under G98, which requires only a notification to the DNO — not a full application.

07G99

The Engineering Recommendation for larger generators exceeding the G98 thresholds. G99 requires a formal application to the DNO and may involve a network study, which can take 6–12 weeks. Larger domestic systems and most commercial installations require G99.

08HES (Home Energy Scotland)

A Scottish Government-funded service providing free, impartial advice on energy efficiency and renewable energy. HES also administers grants and interest-free loans for energy efficiency improvements and renewable installations in Scotland, including solar panels and heat pumps.

09ECO4 (Energy Company Obligation)

A UK government scheme requiring larger energy suppliers to fund energy-efficiency improvements in fuel-poor and vulnerable households. ECO4 runs from 2022 to 2026. Eligible measures include insulation, heating upgrades, and in some cases solar panels. Eligibility is income- and property-based.

10SPEN (SP Energy Networks)

The Distribution Network Operator for the Central Belt, south of Scotland, and parts of England and Wales. If your property is in SPEN's area, your DNO notification or G99 application goes to them. We handle this as part of the process.

11SSEN (Scottish & Southern Electricity Networks)

The Distribution Network Operator for the Highlands, north-east Scotland, and parts of southern England. If your property is in SSEN's area, your DNO notification or G99 application goes to them. We handle this as part of the process.

12ASHP (Air Source Heat Pump)

A heating system that extracts heat from the outside air and uses it to heat your home and hot water. ASHPs work efficiently even at sub-zero temperatures. They are eligible for Home Energy Scotland grants in Scotland. Installation is carried out by our MCS-registered partner.

13RHI (Renewable Heat Incentive)

A former UK government scheme that paid homeowners and businesses for generating renewable heat. The domestic RHI closed to new applicants on 31 March 2022. It has been replaced by the Boiler Upgrade Scheme in England and Wales; Scotland has its own grant programmes through Home Energy Scotland.

14BUS (Boiler Upgrade Scheme)

An England and Wales grant providing up to £7,500 towards heat pumps. The BUS does not apply in Scotland — Scottish homeowners should apply through Home Energy Scotland instead, which offers grants of up to £7,500 plus interest-free loans.

15Gas Safe Register

The official registration body for gas engineers in the UK. Gas Safe registration (559575) is held by our installation partner, Home Heating Services (Scotland) Ltd, covering all gas and heating work.

16TrustMark

The UK government's endorsed quality scheme for tradespeople. TrustMark registration requires adherence to quality standards, financial probity checks, and participation in an alternative dispute resolution scheme. Our installation partner is TrustMark registered (No. 3559930).

17Hybrid Inverter

An inverter that manages both solar panel generation and battery storage in a single unit. It converts DC electricity from the panels and battery into AC for use in the home, and directs surplus energy to the battery or grid. Simpler and often more cost-effective than separate solar and battery inverters.

18Feed-in Tariff (FiT)

A former UK government scheme that paid homeowners for generating renewable electricity. The FiT closed to new applicants on 31 March 2019. Existing FiT recipients continue to receive payments. New installations are now eligible for the Smart Export Guarantee (SEG) instead.

19LiFePO4 (Lithium Iron Phosphate)

A lithium-ion battery chemistry known for its long cycle life, thermal stability, and safety. LiFePO4 batteries typically last 6,000+ cycles (vs. 3,000–4,000 for NMC chemistry), do not suffer thermal runaway under normal conditions, and contain no cobalt. We use Hanchu LiFePO4 batteries.

20Smart Export Tariff

Another name for the Smart Export Guarantee (SEG). Energy suppliers offer varying rates for exported electricity — some are fixed, some track wholesale prices. We help you compare tariffs and sign up after installation. A smart meter or approved export meter is required.