Frequently Asked Questions

A typical 4kW residential solar panel system costs £6,000–£8,000 in Cornwall including installation and 0% VAT (saving you 20% on the total cost). A 6kW system costs £8,500–£12,000. Cornwall generates 3,800–4,200 kWh/year from a 4kW system — 19% above the UK average — giving a typical payback of around 8.6 years solar-only, or 7.2 years with battery storage. Annual savings are typically £700–£1,000.

Yes, solar panels generate electricity from daylight, not direct sunshine. They produce less on overcast days — typically 10–25% of peak output — but they still work. The UK gets enough sunlight for solar to be a sound investment, with average systems generating 3,500–4,500 kWh per year depending on location and roof orientation.

The number of panels depends on your electricity usage and available roof space. A typical UK household uses 3,500–4,500 kWh per year, which a 10–12 panel system (4–5kW) can offset. If you're adding an EV charger or battery, you'll want a larger system. We assess your usage and roof during the free survey to recommend the right size.

The Smart Export Guarantee (SEG) pays you for excess solar electricity you export to the grid. Best current rates (April 2026): Good Energy at 25p fixed, Octopus Intelligent Flux averaging ~25p (32p peak for battery owners), EDF Empower Export at 18p, and British Gas at 15.1p. We register you for the SEG as part of your installation. With a battery, you can store daytime solar generation and export strategically when rates are highest.

No. Solar panels are mounted on rails attached to your roof battens with hooks that slide under existing tiles. No tiles are removed or drilled through. The mounting system is weatherproof and the panels actually protect the tiles beneath from rain and UV damage. We inspect your roof structure during the survey to confirm it can take the additional weight (around 20kg per panel).

Modern solar panels are warranted for 25–30 years and will continue to produce electricity beyond that. Most panels degrade at around 0.3–0.5% per year, meaning after 25 years they still produce 87–92% of their original output. The panels we install from JA Solar carry 30-year product and performance warranties.

A battery significantly increases the value of your solar panels. Without a battery, you typically use only 30–50% of the solar energy you generate — the rest is exported to the grid at 15–25p/kWh. With a battery, self-consumption rises to 70–90%, meaning you use your own free solar energy instead of paying 24.67p/kWh from the grid. A 9.5kWh battery system costs £4,500–£7,000 installed (at 0% VAT). In Cornwall, battery storage typically pays back in 5–7 years.

Modern lithium iron phosphate (LiFePO4) home batteries — including Foxstar and Tesla Powerwall — are warranted for 10 years and designed to last 15+ years. LiFePO4 chemistry is the safest, most stable battery chemistry available, with no thermal runaway risk and excellent long-term capacity retention.

Yes, batteries can be retrofitted to any existing solar PV system. We install AC-coupled battery systems (such as the Foxstar or Tesla Powerwall) alongside your current inverter, compatible with any solar system regardless of age. A retrofit typically takes 1 day and we handle all DNO notifications. The 0% VAT rate applies to battery storage installed alongside solar.

Yes — some home batteries including the Tesla Powerwall and certain Foxstar configurations provide backup power during a grid outage, automatically switching to battery power when the grid fails. This is a particularly useful feature for rural properties in Cornwall where power cuts can occur. Not all batteries include backup as standard, so we advise on this when recommending a system.

Foxstar and Tesla Powerwall are our most frequently installed systems. Foxstar offers excellent value, strong UK customer support, and modular capacity. Tesla Powerwall has a sleeker design, excellent software, and strong backup power features. The right choice depends on your budget, whether backup power matters to you, and whether you want to expand capacity in future. We install both and provide impartial advice.

Yes — retrofit battery storage can be added to virtually any existing solar PV system. We typically install an AC-coupled battery alongside your existing inverter. For older systems with a failing inverter, we may recommend replacing it with a hybrid model. A retrofit installation typically takes 1 day and we handle all DNO notifications.

A new gas combi boiler swap typically costs £1,800–£3,000 fully installed. System boilers with a hot water cylinder cost £2,500–£4,000. Prices vary by brand and complexity — moving the boiler location or upgrading pipework adds cost. We fit Worcester Bosch and Vaillant boilers with manufacturer warranties of up to 10–12 years when installed by an accredited installer.

A straightforward combi boiler swap typically takes 1 day. If we're moving the boiler location, converting from a system boiler to combi, or upgrading pipework, it may take 2–3 days. We always confirm the timeline during the initial survey so there are no surprises.

As a general rule, if your boiler is over 10 years old and needs a repair costing more than £400, replacement is usually more cost-effective. Modern boilers are 90%+ efficient compared to 60–80% for older models, meaning lower energy bills. We can advise on the most cost-effective option during a free assessment.

A gas boiler should be serviced annually by a Gas Safe registered engineer. Annual servicing maintains your manufacturer warranty, ensures safe operation, identifies problems before they become expensive breakdowns, and keeps the boiler running at peak efficiency. Skipping a service can void your warranty and leaves safety checks undone.

A home EV charger typically costs £850–£1,300 fully installed. Popular models include the Zappi (which can divert solar energy to your car), Ohme Home Pro, and Easee One. Installation usually takes half a day. The OZEV grant (£350) is now only available for renters and flat owners — not homeowners in houses. If you have solar panels, a smart charger like the Zappi can charge your car using free solar energy during the day.

Yes — and it is one of the most cost-effective EV charging options available. A smart EV charger like the Zappi or Ohme can detect when your solar panels are generating surplus electricity and automatically divert it to charge your car. On a sunny day, this means effectively free car charging. Customers with solar and a smart EV charger typically source 50–70% of their car charging from solar throughout the year.

If you don't have solar panels, an EV-specific off-peak tariff can save significantly on charging costs. Tariffs like Octopus Intelligent and Octopus Go offer rates as low as 7–10p/kWh overnight, compared to the standard rate of 24.67p/kWh (Ofgem Q2 2026). Smart chargers like the Ohme and Zappi integrate directly with these tariffs to schedule charging automatically. If you have solar, a time-of-use tariff combined with smart charging means you can charge cheaply from the grid overnight and from free solar during the day.

Yes. Retrofit underfloor heating uses slim-profile systems (as thin as 15mm) that can be laid over existing floors. It's most practical during a renovation, extension, or kitchen/bathroom refit. We typically install wet (water-based) systems connected to your central heating, which are more efficient than electric mats.

Absolutely. Single-room underfloor heating is one of the most popular retrofits, particularly for kitchen extensions, bathrooms, and conservatories. A single zone is connected to your existing central heating system via a manifold and zone valve. The project typically takes 1–2 days including screeding or overlay installation.

Key incentives available in 2026: 0% VAT on solar and battery storage (saves 20%, guaranteed until March 2027); Smart Export Guarantee paying up to 25p/kWh for surplus solar; Boiler Upgrade Scheme (£7,500 grant for heat pump installations, runs to March 2028); Warm Homes: Local Grant (up to £30,000 for EPC D–G homeowners with income below £36,000); and ECO4 for qualifying low-income households (runs to December 2026). We help identify and apply for all available funding as part of our service.

MCS certification means the installer meets rigorous industry standards for design, installation quality, and consumer protection. It's required to access the Smart Export Guarantee for solar and is the benchmark for quality across all renewable energy installations. MCS certified installers follow strict quality management processes and their work is independently audited. Always check your installer's MCS certificate number.

Yes. We offer 0% finance options for qualifying customers, allowing you to spread the cost of solar, battery, and other installations over 24–60 months with no interest. Subject to credit approval, finance is arranged through a regulated lender. Ask us for details during your free survey or see our finance page for more information.

For most installations, the timeline is: free home survey (1–2 weeks from enquiry), design and quotation (within 1 week of survey), system order and scheduling (2–4 weeks depending on equipment availability), installation (1–3 days on site). In total, most customers go from first contact to a completed installation within 6–8 weeks.

A hot water cylinder stores domestic hot water ready for use. If you currently have a combi boiler, you do not have a cylinder. Adding a cylinder is worthwhile if you are upgrading to a solar diversion system (the Mixergy cylinder can absorb surplus solar to heat water for free) or improving hot water pressure. We advise on whether your current setup can benefit from a cylinder upgrade during the free survey.

A new unvented hot water cylinder costs £800–£1,500 for the unit, plus installation of typically £400–£700. The Mixergy smart cylinder, which includes solar diversion and AI learning, is our premium recommendation for solar panel owners. Megaflo is our standard recommendation for reliability and mains-pressure hot water.

Cylinder sizing depends on the number of people in your household and peak demand. As a guide: 150 litres for 1–2 people, 200 litres for 3–4 people, 250–300 litres for 5+ people. We calculate the right size based on your household demand as part of our survey.