Guides

Compare specs fairly: official registers before brochures, SCOP at 35 and 55 °C, sound power vs pressure, and usable not nominal battery capacity.

From SCOP and COP to MPPT, OCPP and round-trip efficiency: every technical term on VersusIndex explained, with UK notes on MCS, G98/G99 and OZEV.

Heat pump, solar panels, home battery or EV charger: what to do first and how to combine them. With UK rules on the SEG, 0% VAT, BUS and smart charging.

Where our specs come from – OZEV, ENA, EPREL, Heat Pump Keymark, BAFA and more – what each register guarantees and how we check makers' data nightly.

What SCOP, COP and ηs mean for your bills: median SCOP 4.73 at 35 °C and 3.53 at 55 °C for air-to-water heat pumps, and the BUS minimum of 2.8.

Air-to-water, ground source, air-to-air or hybrid: efficiency at 35 and 55 °C, which types get the Boiler Upgrade Scheme, and data on 1,350 heat pumps.

Permitted development needs 37 dB(A) at a neighbour’s window under MCS 020(a). Distances by sound power, barriers, and data on 996 air source heat pumps.

Size a heat pump the MCS way: room-by-room heat loss to BS EN 12831, design flow temperature and rated output at −10 °C, with data from 1,350 heat pumps.

R290, R32 or R410A: GWP, EU F-gas rules and efficiency. 56% of our air-to-water heat pumps use R290 (propane), with a higher median SCOP at 55 °C.

Boiler Upgrade Scheme 2026: £7,500 for air and ground source, £9,000 when replacing oil or LPG, £2,500 for air-to-air. Eligibility, VAT and noise rules.

How to choose a home EV charger in the UK: why 7 kW suits most single-phase homes, tethered vs socket, smart rules and the OZEV list – data on 67 models.

How UK smart charging works: default off-peak hours, a random delay of up to 600 seconds, time-of-use EV tariffs and charging from solar surplus.

How load balancing stops a 7 kW charger overloading your main fuse, why it matters for DNO notification, and what 60 of the 67 chargers in our data offer.

Home EV charger installation in the UK: the grant for renters and flat owners (75%, up to £500, until March 2027), DNO notification and smart charge rules.

Charging a company EV at home: HMRC treats reimbursed electricity as tax-free under s239 ITEPA if usage is evidenced. How AER works and when MID matters.

What OCPP 1.6, 2.0.1 and 2.1 mean for a home EV charger, how it keeps you free to switch app or tariff, and which of 67 chargers in our data support it.

Usable or nominal kWh? How depth of discharge, round-trip efficiency and standby losses compare across 39 home batteries, with HTW test results.

AC or DC-coupled? When a hybrid inverter makes sense, what backup power needs, and when a battery needs G98 notification or G99 approval from your DNO.

Plug-in solar became legal in Great Britain on 27 August 2026 – but plug-in batteries are outside the new rules. What that means, plus G98 and safety.

Charge cheap, use at peak: how a home battery works with static and dynamic time-of-use tariffs, SEG export, efficiency losses and 0% VAT to March 2027.

How safe is a home battery? LFP vs NMC, what PAS 63100 and the IET Code of Practice cover, where to site it, IP ratings and insurance – from 39 batteries.

How long does a home battery last? Typically 10–12 years, 6,000–10,000 cycles and warranties guaranteeing 60–85% capacity – and what to check.

Split, portable or through-wall monoblock air conditioning: efficiency, noise, installation and UK rules (F-gas, permitted development, MCS 020(a)).

What SEER, SCOP and A+++ mean on an air conditioner label (Regulation 626/2011): class thresholds, climate zones and running costs at the Ofgem price cap.

Air-to-air heat pumps as heating: cost per kWh of heat vs a gas boiler at the Oct 2026 price cap, where they fall short, and the £2,500 BUS grant rules.

Who can install a split air conditioner in the UK (F-gas qualifications), permitted development for air-to-air since May 2025, MCS 020(a) and DIY risks.

How many kW (or BTU) of cooling does your room need? Estimate it from sun, insulation, occupants and ceiling height, with two worked examples.

Watts, efficiency, temperature coefficient and PTC explained with data from 1,000 panels in our database (CEC list), plus TOPCon, HJT, bifacial, all-black.

Product or performance warranty: what does each cover? With measured degradation (median 0.5% a year, NREL), a 25-year worked example and a UK checklist.

How the Smart Export Guarantee works (MCS, export meter, suppliers with 150,000+ customers) and why 0% VAT on solar rises to 5% from 1 April 2027.

How much do solar panels generate in the UK? Official load factors imply about 800–970 kWh per kWp a year. Check your own roof free with the EU's PVGIS.

UK research on 80 solar PV fires found DC isolators and poor installation at the root. What IEC 61215/61730 and MCS mean, and what to ask your installer.

String, microinverter, optimisers or hybrid? What suits shade, a battery, G98 limits and 800 W plug-in solar in the UK, with data from 86 inverters.

How big should your inverter be? 68 of 72 models allow 1.5× panel power. DC/AC ratio, MPPTs, voltage window, input current and the 3.68 kW G98 limit.

Peak efficiency 98.2%, European efficiency 97.35% (medians across 86 inverters). What each figure measures, how weighting works and what it means in kWh.

G98 up to 16 A per phase (notify within 28 days), G99 approval above it, G100 export limits and the ENA Type Test Register, plus 800 W plug-in solar rules.

Inverters need replacing after about 12 years; warranties run 5 years, extendable to 15 (Energy Saving Trust). Siting, IP ratings, alerts, replacement.