Solar and heat pump jargon explained: a plain-English glossary

The short answer

Quotes for solar panels and heat pumps are full of abbreviations. This glossary explains each one in plain English, so you can read a quote with confidence and ask the right questions. Terms are grouped by topic.

Solar panels and electricity

• kW (kilowatt): a measure of power, how fast electricity is made or used at a moment in time.
• kWh (kilowatt hour): a measure of energy, the amount of electricity made or used over time. Your bill charges you per kWh.
• kWp (kilowatt peak): the most power a set of panels can make in ideal conditions. It is how system size is described: a typical home system is about 4.5kWp, roughly 12 panels. See how many panels you need.
• Inverter: the box that turns the electricity your panels make (direct current) into the kind your home uses (alternating current). It usually needs replacing once during the life of the panels.
• Hybrid inverter: an inverter that can also charge and run a battery.
• Self-consumption: the share of your solar electricity you use yourself rather than export. A battery raises it a lot.
• Battery capacity (kWh): how much electricity a battery can store. The Energy Saving Trust says a typical home battery might be 10kWh. See is a battery worth it?
• Payback period: how many years the savings take to cover the cost of the system. Try our solar savings calculator.

Getting paid and your bills

• SEG (Smart Export Guarantee): the scheme that requires larger energy suppliers to pay you for the solar electricity you send to the grid. Rates vary by supplier. See our SEG guide.
• Export meter: a smart meter that records how much electricity you send to the grid, so you can be paid for it.
• Price cap: the most suppliers can charge per kWh and per day on a standard variable tariff, set by Ofgem every three months.
• Time-of-use tariff: a tariff where electricity costs less at certain times, often overnight. Useful with a battery or heat pump.

Standards, rules and paperwork

• MCS (Microgeneration Certification Scheme): the standard for home solar, battery and heat pump installers. An MCS certificate for your system is usually needed for export payments and for government grants and loans.
• RECC and HIES: consumer codes that MCS installers belong to. They set rules on how installers sell and protect your deposit and workmanship. See our checklist for comparing quotes.
• DNO (distribution network operator): the company that runs the local electricity network. Your installer must tell them about your system.
• G98: the simple process for smaller systems (up to 3.68kW of inverter output per phase on a typical home): the installer tells the DNO within 28 days of switching on.
• G99: the process for larger systems, which need the DNO’s permission before installation.
• Permitted development: the rules that let most homes in England fit solar panels without applying for planning permission. See do you need planning permission?
• EPC (Energy Performance Certificate): a rating of your home’s energy efficiency from A to G. Some grants use it to decide who qualifies.

Grants, loans and tax

• 0% VAT: solar panels, batteries and heat pumps installed in homes are zero-rated for VAT until 31 March 2027. See what ends in March 2027.
• BUS (Boiler Upgrade Scheme): a grant of £7,500 off an air or ground source heat pump in England and Wales, or £9,000 until 31 March 2027 for homes heated by oil or LPG with no mains gas connection. See our Boiler Upgrade Scheme guide.
• Warm Homes Loan Scheme: cheaper government-backed loans for solar panels, batteries and heat pumps, available through participating lenders.
• Warm Homes: Local Grant: council-run grants in England for lower-income homes. See our guide to grants and loans.

Heat pumps

• Air source heat pump: a unit outside your home that takes heat from the air to heat your home and hot water.
• Ground source heat pump: takes heat from pipes buried in the ground, in trenches or a borehole.
• SCOP (seasonal coefficient of performance): how much heat a heat pump gives out for each unit of electricity over a year. A SCOP of 3 means three units of heat for every one of electricity.
• Hot water cylinder: a tank that stores hot water. Most heat pumps need one. See how much a heat pump costs.

What to do next

Ready to see what solar could do for your home? Get free solar quotes, or find out more about heat pumps.