I got two quotes for my solar installation on the South Coast. One was from Octopus Energy — smaller system, more conservative panel count, clearly a templated design rather than something thought through for my specific roof. The other was from a local company called AllSolarWorks in Worthing, recommended by a neighbour who had used them the previous year. AllSolarWorks came out, walked the roof, used OpenSolar to model the shading from our chimney stack at different times of year, and came back with a more detailed proposal.
The price difference between the two quotes was not enormous. But what I learned comparing them — and what I have since learned looking at hundreds of real UK quotes in our database — is that comparing solar quotes on headline price alone is essentially meaningless. The one number that cuts through everything else is cost per kWp. Everything else flows from there.
The one number that matters most — cost per kWp
Take the total installed price. Divide by the system size in kilowatt-peak. That is your cost per kWp.
An £11,990 quote for a 4.65 kWp system is £2,578/kWp. A £9,200 quote for a 6.0 kWp system is £1,533/kWp. The second system costs less per unit of generating capacity despite a higher number of panels and a larger total output. You cannot compare the headline prices directly — you can only compare the cost per kWp.
Based on real UK installation quotes from verified buyers in 2026, the typical range runs from around £1,250/kWp at the competitive end to £1,900/kWp at the premium end. Systems with battery storage will naturally show a higher combined cost per kWp. Where possible, ask your installer to separate the solar and battery costs so you can benchmark each independently.
The panels — what the spec sheet is actually telling you
Solar panels are specified by their wattage (how much power they produce under standard test conditions) and their efficiency (what percentage of sunlight hitting the panel is converted to electricity). A 450W panel that is 22% efficient produces the same output as a 450W panel that is 20% efficient — but the more efficient one does it with a smaller physical footprint, which matters on a constrained roof.
The brands appearing most frequently in UK installations right now are Aiko, JA Solar, Jinko, DMEGC, and LONGi. All of these are reputable Chinese manufacturers producing competent panels. The premium tier — REC, SunPower — costs meaningfully more and offers marginal efficiency gains that only really matter if your roof is small or oddly shaped.
The more important question than brand is panel count relative to system size. If a quote specifies 10 panels for a 4.5 kWp system, the implied wattage is 450W per panel. If it specifies 12 panels for the same output, the implied wattage is 375W — older or lower-efficiency panels. Neither is necessarily wrong but it tells you something about the equipment being proposed.
One thing worth knowing: the OpenSolar platform, used by many UK installers, allows them to model your specific roof in 3D and produce a detailed shading analysis showing exactly which panels are affected by chimneys, dormers, or nearby trees at different times of year. An installer who has done this work will show you the annual yield estimate with proper shading applied. One who gives you a generic kWh output without any site-specific modelling has done less work — and their estimate will be less accurate.
Inverters — string, hybrid, and microinverters
The inverter converts the DC electricity your panels produce into AC electricity your home can use. There are three main types in residential installations:
- String inverter — the most common and lowest cost. All panels feed into a single inverter. The limitation is that shading on one panel can reduce the output of the whole string. Fine for unshaded, simple roofs.
- Hybrid inverter — designed to work with a battery from day one. Manages the flow of electricity between panels, battery, and grid. If you are installing solar and battery together, this is usually the right choice — it is cleaner than AC-coupling a battery to a string inverter later.
- Microinverters — small inverters attached to each panel individually, so shading on one panel does not affect the others. Useful for complex roofs with multiple orientations or significant shading. More expensive and more components to potentially fail, but genuinely better performance in difficult conditions.
- Optimisers with string inverter — a middle ground. Panel-level power optimisers (from SolarEdge or Tigo, for example) are added to each panel while retaining a central string inverter. Better shading performance than pure string, cheaper than microinverters.
For most UK homes with a straightforward roof and no significant shading, a hybrid inverter — or a string inverter if no battery is planned — is the right specification. Microinverters on a simple south-facing roof with no obstructions are an unnecessary cost.
What legitimately inflates a quote
Two quotes for the same system size can differ by £1,500–£2,000 for entirely legitimate reasons. Understanding what those reasons are prevents you from dismissing a higher quote unfairly or accepting a cheaper one that has cut corners.
Scaffolding
A simple detached house with good access is straightforward to scaffold. A mid-terrace with a conservatory at the back and a narrow side passage is genuinely more difficult and takes longer. If your quote separates scaffolding as a line item, check whether the figure reflects your actual access situation.
Roof complexity
Multiple roof planes, dormers, hips, and valleys all add installation time. A simple rectangular south-facing pitch takes a fraction of the time that a complex hipped roof with three orientations requires.
Electrical work
If your consumer unit needs upgrading, or the cable run from the roof to the battery location is long or complex, expect additional cost. Some quotes include a line item for "electrical upgrades" that is vague — ask exactly what it covers.
Bird netting
Pigeons nesting under solar panels cause real damage — fouling, nest material blocking drainage, and chewing cables. Netting prevents all of this. It typically adds £200–£600 to a quote and is worth including from day one rather than retrofitting after the problem has already developed. When comparing quotes, strip out the netting cost before calculating cost per kWp — it is a genuine extra, not part of the core system.
G98/G99 grid application
Any system over 3.68 kWp requires a G98 or G99 application to your Distribution Network Operator. This is administrative work that a good installer handles on your behalf. It should be included in the quote — if it is not mentioned, ask.
The warranty picture — what to actually check
Most solar quotes list warranties. Here is what they mean in practice:
- Panel performance warranty — typically 25–30 years, guaranteeing that the panel produces at least 80–90% of its rated output after that period. The catch: this warranty is with the panel manufacturer, not your installer, and only worth something if that manufacturer still exists.
- Inverter warranty — typically 5–12 years depending on brand. Inverters are the component most likely to need replacing during the life of a solar system. Check what the process is if it fails outside the standard warranty period.
- Workmanship warranty — this is from your installer and covers the quality of the installation itself. Typically 5–10 years. This is the warranty that protects you against installation errors, and it is only worth something if your installer is still in business.
- MCS certification — this is not a warranty but it is non-negotiable. MCS is the Microgeneration Certification Scheme, and any grid-connected solar installation in Great Britain must be done by an MCS-certified installer. It is what qualifies you for the Smart Export Guarantee and provides the regulatory framework for your consumer rights. Check the MCS register before signing.
"The GivEnergy administration is a reminder that a warranty is only as good as the company backing it. Ask your installer what support they provide if the manufacturer ceases trading — a good one will have an answer."
How to actually choose between installers
Price is a factor but it is rarely the most important one. The questions worth asking are:
- How long have you been operating, and how many residential installations have you done in my area?
- Can you show me a system design specific to my roof — not just a generic yield estimate?
- What is your process if something goes wrong after installation?
- Are you MCS certified and can I verify that on the register?
- What monitoring system comes with the installation, and how do I access my generation data?
The most reliable route to a good installer remains personal recommendation. My own installer, AllSolarWorks in Worthing, came via a neighbour's recommendation — and two years later they are still responsive when I have questions about system performance. That kind of ongoing relationship is worth more than saving a few hundred pounds on the initial quote. Someone who has had a system installed by a company and is happy two years later is more useful evidence than any review platform. Asking neighbours, local Facebook groups, or the r/solaruk community for recommendations in your area will typically surface the two or three installers who have a genuine track record locally.