Grant Aerona3 vs LG THERMA V

Which Is Better: Grant Aerona3 or LG THERMA V?

Neither is automatically better; the right choice depends on whether you want Grant’s established R32 Aerona3 range or LG’s newer R290 retrofit positioning. According to Grant UK’s Aerona3 brochure, outputs run from 4kW to 17kW with SCOP values from 3.29 to 3.72, while LG’s THERMA V R290 literature (2026) says it can deliver up to 75°C flow temperatures. See also: BUS Grant 2026 guide.

For most homeowners, that means the real decision is not about logo strength but about property fit, installer confidence, and how much weight you put on refrigerant strategy. Read our complete guide to heat pumps in the UK, best heat pump brands guide, and heat pump running costs article. If your home is eligible, our BUS grant survey page is the route for domestic ASHP applications, subject to eligibility.

What Are the Main Technical Differences?

The main differences are refrigerant, high-temperature messaging, and how each system is positioned for retrofit. According to Grant UK’s Aerona3 brochure, Aerona3 uses R32 and quotes SCOP figures between 3.29 and 3.72, while LG Global THERMA V R290 literature (2026) says the R290 monobloc can reach 75°C and operate in outdoor temperatures as low as -28°C.

The broad technical comparison looks like this:

Prices and services correct at time of writing — always request a current quote.

Those figures are not a one-line verdict because the test conditions differ across manufacturer documents. The practical difference is that Grant reads as a more conventional R32 domestic range, while LG is clearly leaning into R290, higher flow temperatures, and stronger retrofit reassurance.

That matters most in homes where radiator suitability and hot-water expectations are near the edge of an easy low-temperature design. In more straightforward properties, installer quality will usually matter more than which brochure sounds more ambitious.

Which One Usually Fits Retrofit Better?

For retrofit, LG THERMA V often appeals more where homeowners want R290 and stronger high-temperature messaging, while Grant often appeals where a simpler mainstream R32 route feels sufficient. According to Energy Saving Trust (2026), heat pumps still work best with good insulation, suitable emitters, and low flow temperatures, so neither brand removes the need for proper room-by-room design.

Grant can make sense where the project needs a known domestic range with multiple outputs and no attempt to oversell “boiler replacement without changes”. LG can make sense where the homeowner is anxious about radiator temperatures, refrigerant choice, or winter operation and wants a system presented as being more explicitly retrofit-ready. In either case, the installer still has to prove the design rather than rely on the sales story.

Typical retrofit decision points include:

1. whether the radiators can support low-temperature heating
2. how much hot-water performance the household expects
3. whether refrigerant choice is a major decision factor
4. which installer can explain the whole system clearly

What Do Installers and Homeowners Most Often Get Wrong?

The most common mistake is treating a hotter published flow temperature as proof that the property does not need radiator or control review. According to MCS (2025), compliant heat pump performance depends on design, commissioning, and handover quality, which means brochure claims only matter if the rest of the system is sized and set up properly.

Another mistake is assuming R290 automatically means lower running costs. Refrigerant matters for product strategy and environmental profile, but electricity bills are still shaped by heat loss, emitter sizing, weather compensation, and user settings. A badly designed R290 system can still disappoint, while a well-designed R32 system can still run very well.

Typical comparison mistakes include:

• choosing based on refrigerant alone
• assuming 75°C means efficient everyday operation
• ignoring hot-water cylinder and control strategy
• comparing model names before comparing installer competence

What Does This Mean in London, Surrey, and TW Homes?

In London, Surrey, and TW homes, the better choice between Grant Aerona3 and LG THERMA V usually depends more on property constraints than on headline marketing. According to Ofgem (April 2026), electricity remains priced at 24.5p/kWh on the typical direct-debit cap, so controls, emitter sizing, and commissioning still matter materially to running costs in real homes.

For terraces, semis, and mixed-age detached houses in the South East, the useful question is whether the installer can show a credible design path. Some homes will benefit from LG’s stronger retrofit messaging and R290 positioning. Others will fit comfortably into a Grant design without needing a premium placed on high-temperature branding.

That is why the local decision should come after survey data, not before it. Our heat pump size calculator guide, heat pump installation process article, and heat pump cost UK guide help frame that decision more rigorously.

It also helps you judge whether paying more for R290 positioning is solving a real design issue. In many straightforward homes, it is the installer route that decides performance. That often improves quote discipline too.

How Electromatic Can Help

If you are comparing Grant Aerona3 vs LG THERMA V, the next step is a survey that checks heat loss, emitters, hot water, and control strategy together before the brand is chosen. According to MCS (2025), compliant system performance depends on documented design and commissioning, not just on the outdoor unit you prefer.

Electromatic can explain where each route makes practical sense in a London or Surrey retrofit and whether the wider project should also include solar panels or battery storage planning. We work under MCS certification via our accredited umbrella partner, and where the installation is eligible we can handle BUS grant applications for air source heat pumps, subject to eligibility. We can also coordinate ASHP and solar through one contractor.

That gives you a property-specific recommendation instead of a generic badge comparison. It also makes it easier to compare competing quotes on scope rather than on marketing language alone.

Book your free home survey →

Call us: 07718 059 284 | Email: admin@electromatic.uk

Frequently Asked Questions

Most follow-up questions on Grant Aerona3 vs LG THERMA V are really about whether one unit is more retrofit-friendly or whether the installer is simply presenting the product differently. According to manufacturer literature and MCS design principles, the full system design still matters more than brand preference alone.

How much does refrigerant choice matter between Grant and LG?

It matters if you care about GWP, long-term refrigerant direction, and product positioning. It still does not remove the need for proper emitter sizing, controls, and commissioning.

Can either system work with existing radiators?

Sometimes yes, but only if the radiators are suitable for low-temperature heating or can be sensibly upgraded. Neither brand makes radiator assessment optional.

Do I need to choose LG if I want higher flow temperatures?

Not necessarily. The better question is what temperatures your home actually needs in normal operation, because efficient heat pump design still favours lower flow temperatures where possible.

Is Grant Aerona3 a weaker retrofit option than LG THERMA V?

Not by default. In some homes Grant is a perfectly sensible fit, especially where the design is straightforward and the installer can prove the numbers clearly.

Which option makes more sense in Surrey and TW homes?

The better option is the one that fits the property, emitters, and hot-water demand most credibly. In South East retrofit work, survey quality usually matters more than badge debate.

The information in this article is for general guidance only and does not constitute financial, legal, or technical advice. Energy savings estimates are based on typical UK household data from the Energy Saving Trust and Ofgem (April 2026 price cap). Actual savings depend on your property type, insulation levels, energy usage patterns, and electricity tariff. The Boiler Upgrade Scheme (BUS) grant of £7,500 is subject to eligibility criteria set by Ofgem — not all properties qualify. Electromatic M&E Ltd operates under MCS certification via an accredited umbrella partner. All installations comply with Building Regulations Part L and MCS standards. E&OE.

Written by Electromatic M&E Ltd — ASHP & Solar installer, London & Surrey (electromatic.uk)

Last updated: April 2026 | Electromatic M&E Ltd, Company No. 13837345