How many solar panels do I need?

This isn't a savings calculation. It's the method a surveyor actually works through, roof by roof.

Start with the roof, not the bill

The roof sets the ceiling on what's possible before anything else gets a look in. A pitched roof facing anywhere from south-east to south-west, with no major shading, is the easiest case: the question becomes how many panels physically fit, not whether solar makes sense at all.

A dormer, a hipped end or a chimney stack eating into the usable slope brings the panel count down before anything else is considered. That's exactly why Pro-Fit prices in four steps rather than one fixed system: a 6-panel array (2.79kWp) suits a smaller roof or a lower budget, and 8, 10 or 12 panels (3.72, 4.65 and 5.58kWp) scale up as the roof allows. The exact figure, how many panels your particular slope takes once the gaps at the edges and between rows are allowed for, is what the survey measures on site, not something a general rule of thumb can give you in advance.

Which way does it face, and is anything in the way?

South-facing is the benchmark everyone compares against, but it's not the only workable direction. East or west-facing roofs still generate well through the morning or afternoon; they just spread generation across the day rather than peaking at midday. A north-facing slope is the one case where we'd tell you plainly that panels on that face specifically aren't worth fitting, even if the rest of the roof works.

Shading is the other half of this. A chimney, a neighbour's tree or a dormer window that throws a shadow across even part of the array for a few hours a day cuts what that section produces, because panels in a string are only as productive as their most-shaded cell. Our surveyor checks this on site, at the time of year and time of day it actually matters, not just by eye on a sunny afternoon.

What does your household actually get through?

Panel count isn't only a roof question. A household that's out at work all day, running the washing machine and the oven in the evening, draws differently from one that's home through the day, charging an EV or running a heat pump on top of normal use. Neither pattern is wrong, but they point towards different places on our four-size table: a smaller array can be the right call for a lower-use household with a modest roof, while a larger one covers more of the household's daytime draw on a house that gets through more power, has an EV to charge, or wants headroom to add a battery later.

This is a conversation, not a form. Bring a recent bill to the survey if you have one, but the real answer comes from walking the roof and talking through how the house is actually used, not from a kWh figure alone.

The grid connection limit most people have never heard of

There's a ceiling that has nothing to do with your roof: how much generating capacity your electricity network operator lets you connect without applying for prior permission. This is governed by a pair of industry standards, G98 and G99, and it matters because it's the one factor in this whole decision that isn't about your house at all.

Under G98, a single-phase home can connect generation of up to 3.68kW (16 amps per phase) by notifying the network operator, which is the straightforward route almost every domestic solar install uses. Go above that, and the process moves to G99, which means applying for and getting permission before you connect, a slower and more involved step. The limit is on the inverter's output to the grid, not on the panels themselves. Only our 6-panel array (2.79kWp) sits under 3.68kW on panel capacity alone; the 8, 10 and 12-panel arrays (3.72, 4.65 and 5.58kWp) all produce more than that on paper, so whether each one still connects under G98 or needs G99 depends on how the inverter's output is set up for your supply. That's confirmed at survey, along with everything else here, and we handle the notification or application paperwork either way, so it's not something you have to manage yourself.

Pro-Fit's four sizes, and what each costs

Here's the published table, the same four builds a surveyor will size your roof against:

Every figure is a guide price, fixed in writing after a free survey. Each one includes the panels themselves (DMEGC 465W all-black), a hybrid inverter that's battery-ready from day one whether or not you take a battery now, scaffolding arranged and paid for by us, bird protection, a monitoring app set up before we leave, the grid connection paperwork covered above, and help registering for export payments. See the full pricing table for the detail behind every figure, including what's covered and what can be an extra at survey.

If a battery's part of the plan, we've written a separate guide on whether a battery's worth adding to your household and, once that's decided, how to size one.

The method in one list

1. Measure, or have us measure, the usable roof slope: south-east to south-west is the easiest case, and a surveyor will tell you plainly if a face isn't worth using.
2. Check what shades it, at the time of day and time of year it actually happens, not just a quick look on a bright afternoon.
3. Think honestly about how the house uses power: out all day, home all day, an EV, a heat pump. All of it shifts which size earns its place.
4. Match what the roof and the household point towards against Pro-Fit's four published sizes, 6, 8, 10 or 12 panels.
5. Get a free survey. That's where the roof, the shading and the grid connection all get confirmed together, and where the guide price becomes a written one.

Book a free survey and we'll work through all of this on your roof, not a generic one.