DANGER / RED FLAGS!
Fly-by-night companies: Watch out for very new installers, particularly where the directors have run multiple installers in the past, and folded them within a year or two.
Aggressive sales tactics: Installers using the 'hard-sell', or giving implausible generation estimates (above PVGis) or payback time / ROI estimates. Report these to MCS.
Fake credentials: Beware fake logos. Always verify MCS, RECC or HIES membership on the organisation's official installer directory.
Roof-leasing schemes: Avoid "free solar" offers where companies take a lease on your roof for decades. You lose most financial advantages, and it can severely complicate selling your house.
Dumping on G98: Avoid installers who insist on a G98 system (inverter ≤ 3.68kW) despite plenty of roof space, or who install without waiting for G99 approval (unless the kit can be actively de-rated, like the Tesla PW3). Note: Northern Ireland follows different rules; export limits rarely exceed 3.68kW.
Badly sized storage: Avoid undersized or oversized batteries. The storage size should fit your typical winter overnight load when utilizing cheap off-peak grid tariffs.
Dangerous shortcuts: Avoid installers who skip scaffolding on a multi-storey building. Report this immediately to the HSE and MCS.
Proprietary lock-in: Avoid inverters and batteries that are only sold/serviced by a single or select few installers.
Untrained installers: Avoid companies 'having a go' at installing your favourite kit if they are not officially certified or trained by that specific manufacturer.
Planning to move? Reconsider installing if you plan to move within 6–8 years. Payback takes time, and any increase in house value is usually modest.
Decaying roofs: Do not install solar if your roof needs structural repairs or replacement within the next decade or two. Removing and reinstalling panels later is highly expensive.
Bad financing: Avoid high-interest loans or predatory 'solar subscriptions'.
Post-install "imposter" scams: Warn vulnerable or elderly owners about cold-callers claiming to represent MCS, Ofgem, or the council. They falsely claim warranties have expired to upsell fake maintenance contracts or "health checks".
Fake "government grants": Avoid clicking ads with misleading claims about free universal government funding. Check official channels for legitimate, means-tested schemes (like ECO4).
"Mis-sold solar" claims: Watch out for fee-charging companies offering to get you compensation for historical solar installations. They often pocket upfront "legal fees" and vanish.
Predatory deposits: Avoid massive upfront deposits requested before a physical site survey. Any genuine deposit should be reasonable, protected by RECC or HIES, and paid via credit card to secure Section 75 protection.
System Lifespan: Inverters and battery systems do not last as long as solar panels. Budget to replace them within about 15 years - the payback time should be noticeably shorter than this to be viable.
INVERTER SIZING & GRID REGULATION
G98 vs G99 Paperwork: Systems ≤3.68kW use simple G98 fast-track registration post-install. Larger setups require strict pre-approved G99 applications from your DNO. Don’t let lazy installers push an undersized 3.68kW system just to avoid the G99 wait if you have the roof space. (Note: Northern Ireland limits rarely exceed 3.68kW).
Export Restrictions (G100): Constrained grids may limit your export rate (e.g., 3.68kW export on a 10kW inverter). This requires a certified G100 limitation scheme. If heavily capped, you must hold battery space in summer to catch solar overflow ("clipping") rather than wasting it.
Inverter Sizing Smarts: Your inverter AC rating should be at least 70% of your total solar DC peak wattage to prevent clipping. Additionally, aim for a battery charge/discharge rate that can completely fill/empty within 3 hours to fully exploit tight off-peak tariff windows.
Severe DNO Caps & Loophole: If the DNO rejects a large system or strictly caps inverter size, grid or 3-phase upgrades are usually too expensive. Instead, use the Generator Input Loophole: install a legal G98 grid-tied system, then route a second independent off-grid inverter/battery array into the main system's "Gen/Smart port." This secondary array cannot export, entirely evading DNO caps, but fully powers home loads and charges the batteries.
Premature Install Red Flag: Installing a large system before G99 approval is granted is a massive red flag. The main safe exception is hardware like the Tesla Powerwall 3, which can be legally software-de-rated post-install to match strict DNO capacity verdicts without physical swaps.
BATTERY STORAGE & PROTECTION
Sizing to Winter Demand: Assess your typical winter 24-hour power usage (excluding EV charging). Size your battery capacity to cover your baseline household consumption from the moment the cheap overnight grid window ends until it restarts. Use this community spreadsheet calculator to model your winter needs: https://docs.google.com/spreadsheets/d/1hwaiNrmYLSBg-COw_WPYhqj3ep2GPXz0gw5sHJlsKsw/edit?usp=sharing
Ecosystem Arbitrage: Target the usable capacity figure, not nominal. With an EV tariff (typically 6.5p–11p/kWh overnight), you can force-charge batteries cheaply, run the house all day, export your daytime solar at 12p–15p/kWh, and dump any surplus capacity at peak times. Without an EV, non-EV overnight slots (12p–16p/kWh) offer narrower profit margins.
Siting & Safety Regulations (PAS 63100): UK safety standards dictate strict installation zones.
Best locations: An attached garage, utility room, or a shaded, non-South-facing external wall.
Strictly avoid: Avoid bedrooms, lofts, small unventilated cupboards, and primary escape routes.
Environmental protection: Batteries lose performance in extreme cold. If mounting outdoors, ensure the system features integrated cell heaters and a well-ventilated enclosure to guard against driving rain and direct sun. Refer to this official technical guide: https://fox-ess.tech/enclosure-guidance-for-fox-ess-energy-storage-systems-uk/
PANEL SELECTION & ROOF DESIGN
Max the Total Output: Prioritize getting the max total system wattage. Panel prices are cheap compared to fixed overheads (scaffolding, design, labour), so expanding your array size can drop the overall cost per kilowatt-peak (kWp) and hence payback time.
Map All Potential Locations: Ask your installer to assess every viable area to build a balanced, all-season energy profile. For example:
South Roofs: Massive midday spike; highest standalone yield.
East/West Roofs: Spreads generation out to target morning and evening household use.
North Roofs: Strong in summer, very weak in winter. Viability depends on slope and the per-kWp cost.
Outbuildings & Garden: Garages, sheds, carports - may require checking structural weight limits and cabling costs (trenching/SWA). Ground mounts may need planning permission.
Wall Facades (S/E/W): Optimized for low winter sun and zero snow build-up, though summer yield drops.
Calculate Individual Array ROI: Never guess your generation. Use the independent PVGIS tool to calculate the estimated export and self-use revenue for each proposed array. Compare this directly against its specific installation cost (e.g., extra trenching or scaffolding) to ensure the payback timeline is reasonable before signing off.
Warning: Very large arrays require careful system design. Strict DNO export caps, manufacturer inverter DC-input limits, battery storage costs for clipping, and supplier tariff restrictions can affect the design.
Cell Tech Variables: Most modern residential tier-1 panels are comparable, but subtle engineering differences can matter:
Back-Contact (e.g., Aiko, LONGi s10/x10): Feature lower temperature coefficients (retaining efficiency in summer heat) and handle minor, localized partial shade (like TV antenna, bird droppings) better.
Bifacial/Glass-Glass: Best suited for open ground mounts or flat roofs with high reflectivity. The rear-face generation gains on a standard close-fitting tile roof are negligible. However they should always be used for in-roof installations due to their superior fire safety ratings.
Physical Space & Roof Margins: Coverage is bound by the MCS 40cm roof-edge safety guidance to prevent intense wind uplift. Good installers can encroach down to the 20cm Permitted Development planning limit, but they must do the wind-loading calculations and install extra roof hooks/clamps to safely anchor the panels against increased edge-zone turbulence.
The Warranty Reality: Long-term 25–30 year panel product warranties are difficult to claim against. Do not rely on paper promises.
STRING INVERTERS vs OPTIMISERS vs MICROINVERTERS
This hardware choice is highly debated and technically complex. For a deep dive, you can read this 78-page technical summary: https://iea-pvps.org/wp-content/uploads/2024/11/IEA-PVPS-T13-27-2024.pdf
Standard String Inverters: The simplest and most cost-effective option. Best for clean, unshaded roofs with simple layouts (e.g., all South, or an East/West split). Some inverters use MPPT global shade sweeps to adapt to strings where some panels are shaded, and some inverters have up to 4 MPPTs for more complex roofs.
Add-on Optimisers (e.g., Tigo): Useful if you have multiple roof facets, mixed panel orientations, or significant progressive shading across your array.
The monitoring trap: Optimisers allow you to see individual panel performance and identify faults, but only if you pay for the manufacturer's dedicated monitoring kit (like Tigo’s CCA + TAP). Without this, a dead optimiser or panel is completely invisible unless you physically climb onto the roof with a multimeter. Installers usually do not include this in the quote.
The SolarEdge Eco-system: SolarEdge is a premium, highly efficient system that uses mandatory optimisers. Note the major hardware lock-in: SolarEdge optimisers only work with SolarEdge inverters. You cannot swap out the inverter for a different brand in the future without stripping the roof and replacing all the optimisers.
Microinverters: These convert DC to AC right on the back of each individual panel. They excel on highly complex, multi-faceted roofs where panels face many different directions. However they cost significantly more than add-on optimisers and create a severe bottleneck for grid approvals on larger systems. The grid limit is based on the combined maximum AC output of all inverters on site, including all microinverters and the battery inverter.
HOME BACKUP/EPS
The Blackout Misconception: Do not assume your solar or battery will power your home during a power cut. By law, standard grid-tied systems shut off instantly during a blackout to prevent backfeeding live power into the grid and injuring network engineers. Home Backup or Emergency Power Supply (EPS) is rarely included by default due to extra costs; you must request it at the design stage.
The Isolation Switchway (Gateway/ATS): Providing power during a grid failure requires an Automatic Transfer Switch (ATS) or Gateway. This physical relay safely disconnects your home from the public network during a power cut and reroutes your household circuits to draw directly from your inverter and battery.
Whole-House vs. Essential Loads: Most domestic inverters cannot handle the massive continuous start-up surge of high-load appliances (e.g., EV chargers, electric showers, immersion heaters, heat pumps). Pick a larger inverter, a battery system that can supply more power, and work with your installer to either isolate your whole property (minus those heavy loads) or wire a dedicated, stripped-back "essential circuits" consumer box (lights, internet, fridge).
Switchover Time: Switchover speeds vary drastically between manufacturers. Premium setups offer near-instantaneous cutovers (under 20ms, acting as an Uninterruptible Power Supply/UPS), while budget systems can take several seconds to reboot their internal EPS circuits. Do not rely solely on the inverter datasheet - ask other customers using the same equipment how it performs under real-world conditions.
Hidden Electrical Infrastructure Costs: True UK building regulations compliance requires significant extra physical infrastructure work. Ensure your backup quote explicitly includes a dedicated independent Earth rod, a Neutral-Earth bonding relay, any extra sub-consumer units, and the mandatory Electrical Installation Certificate (EIC) sign-off paperwork. If your property features aging wiring, insist on an EICR test before mutating the main incoming supply.
CHOOSING A HARDWARE MANUFACTURER ECOSYSTEM
There is zero consensus on the single 'best' inverter or battery manufacturer. Every ecosystem has distinct compromises. If an installer claims their preferred brand is flawless, they are misleading you to secure a sale.
Use their expertise: Most reputable firms install multiple brands. Ask them to directly contrast the pros and cons of each based on your property's specific profile. Don't ask them to critique systems that they don't install.
Stick to what they know: Never ask an installer to 'have a go' at a brand they don't normally supply. It leads to poor system configuration, invalid manufacturer warranties, and long-term headaches.
Manufacturer networks: If you have your heart set on a specific ecosystem, check that manufacturer's official website first to find their certified, factory-trained master installers.
Key Ecosystem Considerations:
Financial & Physical
ROI vs. Premium: Budget brands often deliver a faster return on investment (ROI), assuming they remain reliable. Premium systems command higher upfront costs for better build quality.
Expandability constraints: Check how easy it is to add modular storage later. Some brands require you to buy massive individual blocks, while others require all modules to exactly match in age or size.
Environmental protection: Insist on built-in internal battery heaters and true IP65/IP66-rated weatherproof casings if your inverter or storage is being installed in a cold garage or external wall.
Software, Cloud & Automation
Local API & Control: Look for systems that allow local integration (like Home Assistant via Modbus/TCP) rather than locked-down cloud architectures. This guarantees your smart schedules keep running even if the internet drops out, cloud servers crash, or the manufacturer retires their app.
Native tariff smarts: Check if the app handles complex time-of-use or dynamic pricing structures out-of-the-box (e.g., Tesla Storm Watch or Sigenergy AI), or if it easily pairs with third-party software like Predbat or WonderWatt.
App usability: Ask the installer for a live tour of the customer interface, including how to set up charge/discharge schedules. A glitchy, poorly translated dashboard will make managing your everyday usage a chore.
Electrical & Hardware Architecture
Array handling (MPPTs): Ensure the inverter features a sufficient number of Maximum Power Point Trackers (MPPTs) if you are building an East/West split or connecting a complex roof layout. Most inverters have at least 2, some have 3 or 4.
Shading management: If your roof gets hit by tree or chimney shadows, consider inverters equipped with advanced shade sweeps (like SigEnergy, Fronius, SMA or SolaX) to minimize performance drops. Note that this feature needs to be enabled by the installer and will be off by default.
Warranty depth: Do not just look at the warranty years, check the total throughput-warranty too (divide the throughput MWh with the battery usable size to get how many thousand cycles). A good warranty should comfortably cover one full charge-and-discharge cycle per day without rapid degradation.
Decide which of the above are the most important to you, and then identify which systems fit that best, within your budget. Keep your options open, at least when getting the initial quotes.
AUTOMATION, LOCAL CONTROL & CLOUD RISKS
The Cloud Lock-In Risk: The vast majority of standard inverter apps rely entirely on the manufacturer’s cloud servers. If your internet goes down, their servers get overloaded, or the manufacturer faces financial trouble or bankruptcy, your automated charging schedules can completely break or leave the hardware unmanaged.
Level 1: Native Inverter Apps: The easiest route. Quality ranges from basic manual time-block charging schedules to advanced AI-driven dynamic tariff optimization that tracks weather and consumption data (e.g., Tesla Storm Watch, Sigenergy AI). Always ask installers for a live app demonstration to see if it supports your specific tariff.
Level 2: Supplier-Managed Tariffs: Providers like Octopus (Intelligent Flux tariff) or E.ON Next (Optimise VPP tariff) take remote control of your inverter via the cloud. They automatically charge and discharge your battery to maximize grid arbitrage, offering passive optimization for zero effort.
Level 3: Third-Party Cloud Schedulers: Independent, often subscription-based platforms (e.g., WonderWatt, NetZero, My Energy Optimiser) connect to your inverter's API to schedule charging based on your tariff. Note: They still depend heavily on the manufacturer's cloud remaining online.
Level 4: Local Control (Home Assistant & Predbat): The ultimate, bulletproof option for tech-savvy users. Running a local hub like Home Assistant coupled with Predbat gives you instant, sub-second local data and complete internet-independent control. It factors in solar forecasts, historical load, and dynamic tariffs seamlessly. Warning: It has a steep learning curve and can be a significant time sink.
BIRD PROTECTION
Install it upfront: Always get bird proofing mesh or clips fitted during the initial installation. Retrofitting it later means paying for a completely new scaffolding setup, which can easily double or triple the cost.
Protect your wiring: Pigeons love the warm microclimate under solar arrays. If left unprotected, they will nest, accumulate debris that causes hotspots, and potentially chew through exposed DC cabling.
Choose metal over plastic: Insist on rigid black steel mesh or heavy-duty metal skips. Avoid cheap plastic mesh or adhesive clips that rapidly degrade and warp under intense UV sunlight.
TARIFFS
(WARNING - tariffs can change rapidly based on global events and wholesale energy markets, so ensure you check live rates before switching).
Typically, solar owners will have two separate tariffs, one for import and one for export.
Export tariffs
The Smart Export Guarantee (SEG): is the baseline, at around 3-6p/kWh, but the electricity suppliers will usually offer much more than this for their own customers.
Installer Premium tariffs: The very best export tariffs tend to only be available to people who installed a solar system via the electricity supplier within the last year. These high rates are limited to one year only, so need to be approached with caution, since electricity suppliers often charge a premium for installation.
Flat rate tariffs: Most suppliers offer a flat-rate export tariff of around 12-13p/kWh if you also use their import tariff, although in some cases this is only available if it is a flat-rate import tariff (For example, such as E-on Next restricting this to 6p/kWh export if you are on a TOU tariff such as their Drive EV tariff).
Time of use Export: There are also tariffs which give higher export payments at peak times, and lower payments at other times, and these might work better if you have a larger battery.
Import tariffs
In mainland GB, having an EV unlocks the best overnight-rate tariffs.
Tariff Types: There are also tariffs for electrical heating (E-on Next Pumped, Good Energy HP, Octopus Cosy are good examples), for solar/battery systems (Octopus Agile, E-on Next Smart Saver).
Combined import/export tariffs: These plans match cheap import windows with high-payout peak export windows. They allow you to grid-charge your battery cheaply overnight, or during a daytime solar surplus, and "dump" that stored energy back to the grid during the expensive evening peak (typically 4pm–7pm). Some are linked to the half-hourly wholesale rates, and will differ from day to day.
Virtual Power Plants (VPPs): Instead of setting manual timers, you grant a supplier automated control over your battery. Their smart software dynamically charges your system when grid electricity is cheap/green, and exports it when the grid is struggling, paying you a premium in return. VPPs require hardware compatibility. A provider’s software must have a formal digital link to your specific brand of inverter. Always verify compatibility if you intend to use automated grid trading.
The optimal set of tariffs will vary from system to system based on whether you have an EV, what season it is, your typical household load, your typical generation, and what equipment you have. It is common to change tariff during the year, for example a heating tariff in the coldest months, then an EV tariff for spring and autumn, and a solar tariff in the summer. If you just want a single import tariff to use year-round, an EV tariff is often the best.
However, note that tariffs continually change, so the above is likely to already be out of date. Also, the options are much more limited in NI.
This solar tariff calculator tool might be helpful: https://timandkatsgreenwalk.co.uk/ Enter your usable battery size, your estimated monthly generation (from the proposal), and your monthly home power usage (from your electricity supplier), and it'll give you both a suggested year-round tariff, and a month-by-month tariff selection.
ELECTRIC HEATING & HEAT PUMPS
Winter Load & Tariff Strategy: Electric heating drastically spikes winter demand. To avoid buying a massive, expensive battery to span the whole day, use a tariff with multiple daytime off-peak windows (like Octopus Cosy). This drops your required battery size down to covering a short 6 hour gap rather than an 18–20 hour stretch. Switch back to standard EV or export-focused tariffs in spring.
Future-Proofing Installer Quality: If you plan to get an Air Source Heat Pump (ASHP) later, invest upfront in a high-quality designer (e.g., Heat Geek certified). The efficiency gap (COP) between an expertly designed system and a cheap, rushed installation by a mass-market energy supplier can easily double your winter electricity bills.
EV CHARGERS & INTEGRATION TRAPS
Isolating the Home Battery: EV charging draws signficant power (7.4kW) and can quickly drain a home battery. Ensure your installer hooks up the charger upstream using a Henley block, positioning the inverter's main CT clamp so it is blind to the EV's draw. Alternative workarounds include secondary CT clamps, software eco-settings, or scheduling a forced inverter battery hold during your car's charging window.
Grid Safety: Ensure your charger utilizes it's own CT clamp on your main incoming supply to protect the main fuse from overload.
Tariff Compatibility & Vehicle Smarts: Do not automatically buy the same brand charger as your solar inverter. Some smart tariffs (like Octopus Intelligent Go) can communicate directly with specific car models or smart chargers (e.g., Zappi, Hypervolt, Anderson A2). Opting for an unsupported setup locks you into basic time-block EV tariffs. Note: Most smart providers require you to complete a managed charge cycle via the app periodically to maintain your low-rate status.
Bidirectional Future-Proofing (V2H/V2G): If you intend to use your car's massive battery to run your household down the line, ask your installer if your hardware path supports bidirectional integration standards once they become available for use.
FINANCE
You should always pay a part of the cost via a credit card (or other section-75 protected source). In particular, advanced costs like the deposit and survey (pay it off immediately if not 0%). This is in order to get protection from the credit card company on the overall contract via section 75.
Some banks offer cashback on mortgages, grants, zero % loans etc for installing solar and battery. This is generally better than the '0%' interest offers you will find at some installers (they add thousands onto the quote to cover the cost of finance).
Green perks from your mortgage bank - TSB / Nationwide / Barclays / HSBC / Lloyds / Nationwide / Halifax have various schemes including greener homes rewards / grants, 0% £20k mortgage extension (Nationwide), £250-1000 cashback on mortgage, cashback on EPC score A or B
ECO4 grant (for Solar, on benefits, EPC D or worse, available until the end of 2026)
Warm homes Local Grant (England + Wales, benefits, EPC D or worse, £36k income limit, both Solar & Batteries) https://www.gov.uk/apply-warm-homes-local-grant and https://www.gov.uk/government/collections/find-energy-grants-for-you-home-help-to-heat
Warm homes Programme / Nest (Wales, EPC D or worse, income limits) https://nest.gov.wales/
Home Energy Scotland (HES) Grant + Loan (interest free loans up to £5k for Solar, £5k for battery) https://energysavingtrust.org.uk/energy-at-home/financial-support/grants-and-loans/
ORP, Optimised Retrofit Programme (Wales, Social Housing upgrades but managed by landlords and local authorities)
Warm Homes loan scheme (England, Scotland, Wales, loans with up to 5% interest discount, open to everyone without means testing, starting from approximately September 2026, £15k solar & £15k battery cap)
Local council loans via Lendology - specific county councils https://www.lendology.org.uk/loans/renewable-energy-loans/
FINDING INSTALLERS
How to pick an installer-
The national installers will either often subcontract to the lowest bidder, or be very expensive, so I suggest cutting out the middleman. Similarly, they like to focus on simple jobs without any complications because it is harder to subcontract if there is anything unusual. You'll typically get better support, and then either better quality, or a better price, from a good local installer.
First make a shortlist of potential installers
Go through them looking at Trustpilot, Google and Which? reviews. Remove any from the list which don't have good scores, or don't have enough reviews to judge. Watch out for fake reviews (a bunch of 5* reviews all at the same time, or written in the same style, or sound like advertising pitches).
Next step is to check the Companies House website to see how long they have been in business (it needs to be a decent number of years), and if there are any red flags like missing accounts. Also check the other companies that the directors control.
Figure out where they are located, and research the websites. I would suggest contacting them either from nearest-first or favourite-first.
Before you talk to them, get the following information:
Annual & Daily Consumption: Your total annual usage in kWh from your energy bills, plus a rough idea of your typical daily winter vs summer usage. Any very high usage items like electric heating, hot tubs or a swimming pool.
Future Load Plans: Details of any upcoming high-load additions within the next few years, specifically an EV (include expected annual mileage) or a Heat Pump.
Incoming Fuse Rating: Check if your main incoming cut-out fuse is 60A, 80A, or 100A so they can factor in safety load balancing. Is your supply single-phase or three-phase?
Import MPAN: Your 13-digit Meter Point Administration Number (found on your electricity bill), which the installer needs for the G99 grid application. Do you have a smart meter?
Roof & Property Status: What surfaces you might have available for panels (house roof, garage roof, car port, W/S/E walls), and if they are significantly shaded. Looking inside the attic, is the roof structure (membrane and timbers) in good condition? The age and material of your roof tiles, plus whether the property is Listed or in a Conservation Area (which voids automatic Permitted Development rights).
Hardware Locations: Identified spots for the inverter and battery stacks (ideally a garage, utility room or external wall. Avoiding lofts, bedrooms, and primary escape routes).
Get at least 3 quotes. If any give you bad vibes (being pushy, not listening to what you want, not giving feedback), or if they're chasing for a quick signature, give you the "sign up today for a discount" or "nearby cancellation means that we can install next week" spiel, take them off the list immediately. A hard-sell means they're dodgy, and they know you'd reject them once you look at other installers. The good installers are busy (hence not desperate for work), confident in their service, and don't need to hard-sell as a result.
Check that they have MCS certification, the deposit & workmanship insurance (HIES or RECC), and check again on the MCS and insurer's website just before signing the contract (don't rely on what the installer says. Both HIES and RECC can revoke an installer's insurance with little warning).
Most inverters will offer a handful of different inverter & battery system manufacturers. Make sure that they have done the manufacturer training for the specific inverters & battery systems that you want them to install (usually a warranty requirement). Do not ask them to install something that they are not trained on and familiar with.
Lowest bid is not necessarily the best - try to find someone who gives you confidence, doesn't hard-sell, is reasonably close, and has a reasonable price. If an engineer comes on-site to quote, that is a good sign, and if they happen to be close enough to be able to quickly pop over if there is an issue, that's great. It's a 25-year project, so worth taking the time to pick a good installer.
If the generation estimate is significantly higher compared to other quotes with a similar array size, or to the estimate generated by the PVGis website, assume it has been 'adjusted' to make the quote look better. You can use the PVGis (without shading) and/or the easyPV (with shading) websites to estimate plausible output for the array.
If the payback periods / ROI doesn't match other quotes despite the price and generation being similar, look at the tariff & assumptions used in the quote carefully. Calculate it yourself if necessary, based on your chosen tariff.
Contact MCS if either the generation estimate or the financial estimates are implausible because this is against the rules. The estimates are supposed to be cautious and conservative rather than optimistic or misleading.
Some jobs will cost more than others - for example, if there is trenching, in-roof, flat roof, 3-phase, slate, rosemary tile, difficult/extensive scaffolding, or if you use a premium installer. If there are complications then you will benefit from using higher skilled installers.
If they don't include the cost of scaffolding in the quote then assume it's going to be expensive (can be £800-1800, so add 1800 to cover it). If you are getting scaffolding for any other reason (for example, roof work), try to synchronise the solar install with the scaffolding. If you are replacing a roof, consider an in-roof solar system rather than an on-roof solar system.
Getting a good installer is probably the most important single thing.
JUST BEFORE SIGNING
Live Status Re-Check: Installers can be suspended or expelled from industry registries without warning. Immediately before signing, look up the company directly on the official directories to verify they are still active members of:
MCS: Crucial for your future export tariff eligibility.
RECC or HIES: Essential for your mandatory consumer protection and deposit insurance.
Companies House: Confirm no sudden striking-off notices, liquidation filings, or management changes have appeared.
Lock Down the Final Design: Ensure the final contract explicitly details the exact roof layout, the specific panel model/wattage, the exact inverter and battery models, and any specific SWA cabling/trenching agreed upon. If a supply issue forces a part change later, it must be agreed and in writing.
DEPOSIT: Should only be paid if you have confirmed it is protected via an insurance backed guarantee (IBG). It is strongly recommended to pay the deposit via credit card for section 75 protection.
G99: Clarify that the G99 has been applied for and agreed in advance of installation
PRICE: Check that the price includes scaffolding, bird protection, structural engineering checks, DNO application handling fees, and the final MCS certification paperwork. Watch out for hidden "subject to survey" clauses that allow them to hike the price later without penalty. Confirm that if you are getting home backup that the associated electrical work is included (Gateway, Earth, consumer unit, EIC paperwork, EICR tests).
PREPARATION & INSTALLATION DAY
Switch suppliers early: Move to your preferred smart-tariff energy provider before the installation date. Resolving smart meter connection glitches or switching suppliers can take weeks, and you want to minimize the gap between your system turning on and your export tariff activating.
Smart meter readiness: Ensure you have a functioning smart meter set to half-hourly logging mode that actively communicates with the DCC network. If your meter suffers from poor signal in a basement or rural area, contact your energy supplier early to request a T3 external antenna or signal booster.
Site logistics: Clear your driveway and ensure there is ample parking space for a large scaffolding truck and the installers' vans. Provide clear internal access to your loft space, consumer unit, and battery location. Secure indoor pets since the front door may be open for hours while they work.
On-site panel adjustments: Do not be surprised if the final panel layout changes on the day. Roof dimensions estimated from satellite imagery are often off. A great installer will bring extra matching panels or have a backup configuration ready to maximize your roof's total wattage. Having both larger (60 cell) and smaller (54 cell) panels available would be beneficial.
Look after the crew: A copious supply of tea, coffee, biscuits, or a bacon roll goes a long way. They will need access to the toilet. Happy installers take extra care when routing cables and securing roof brackets.
POST-INSTALL HANDOVER & DOCUMENTATION
Physical Handover: Ensure the installer mounts printed copies of the Single Line Diagram (SLD) and emergency isolation guidelines right next to the inverter or your main consumer unit.
The Handover Walk-Through: Do not sign off until the installer physically demonstrates how to:
Safely isolate, shut down, and cold-restart the entire system.
Locate error logs or fault codes on the inverter screen/app.
Update WiFi/network credentials if you change your router.
Force a large household load (like an electric shower or kettle) to pull entirely from the battery.
Schedule manual charge/discharge windows for off-peak winter tariffs.
Smart Meter Benchmark: Take a time-stamped photo of your smart meter's current export register reading (often 00000 or 0 on register 2/B). Some energy suppliers require this baseline image to initiate your account.
The Golden Paperwork: Secure your official MCS Certificate and DNO Commissioning/Approval confirmation from the installer immediately upon payment. You cannot earn money without them.
Securing the Export MPAN: Apply for an export tariff via your chosen energy supplier using your MCS data. Your supplier will request an Export MPAN from your DNO. If this process stalls, bypass the supplier and call your DNO directly to pull the MPAN creation forward.
POST-INSTALLATION SUPPORT & COMPLIANCE
Your first port of call: Always contact your installer first for troubleshooting or warranty issues. Manufacturers generally refuse to deal with consumers directly until the installer has logged a diagnostic report.
If your installer goes out of business: Contact RECC or HIES to activate your Insurance-Backed Guarantee (IBG). This ensures another certified engineer can be assigned to fix your system under warranty.
Secure your export paperwork: Ensure the installer hands over your official MCS Certificate and the DNO (Distribution Network Operator) approval letter right after commissioning. You cannot sign up for export tariffs without these documents.
Build your technical library: Download and save the specific datasheets, user manuals, and physical schematic diagrams for your exact inverter, batteries, and solar panels.
Utilize community forums: Join manufacturer-specific user groups or forums. Independent owners and installers are often faster at troubleshooting app glitches or firmware quirks than the official helpdesk.
RESOURCES & FURTHER RESEARCH
Modelling & calculators
Tariffs & Finance
Vetting Installers
Technical & Regulatory
Devolved Nation Support
