Solar & Battery, Explained Without the Sales Pitch
Most solar quotes lead with how much electricity the panels generate. That is the wrong number. What changes your bill is how much of that generation you use yourself instead of exporting it for pennies — and that is decided by your battery and your habits, not by the panels.
Written by an MCS-certified installer • No obligation • Includes the parts that argue against buying
We are an MCS-certified installer working across Nottinghamshire, Derbyshire, Lincolnshire, Leicestershire and Yorkshire, and approved installers for Tesla Powerwall, SolaX and SolarEdge. Everything below is what we would tell you on the phone — including the parts that argue against buying.
What solar actually saves — and the number nobody quotes
A well-oriented, unshaded roof in the East Midlands generates roughly 900 kWh per kWp per year. A ten-panel array at 450 W a panel is about 4.5 kWp, so around 4,000 kWh a year. That sounds like it should wipe out a typical 3,500 kWh household bill. It does not, and here is why.
Your roof peaks at noon. Your house peaks at seven.
Solar generates in a single arc across the middle of the day. Household demand is the opposite shape — a spike at breakfast, a trough while everyone is out, and the real load in the evening once the panels have stopped. Only the shaded overlap is money saved.
The arithmeticYou avoid roughly 26p for every unit you use yourself, and earn roughly 7p for every unit you export. Same array, very different outcomes.
Generation is not the same as saving
Solar generates at midday. Most households use electricity at breakfast and in the evening. Without storage you will typically use only 25–35% of what you generate. The rest is exported.
Exported units are worth far less
You avoid roughly 26p per kWh you use yourself. You earn roughly 7p per kWh you export — under a quarter of the value. Two identical arrays can save very different amounts.
So the honest figure
Panels only, typical family home, south-facing: expect around £500 a year against an installed cost of roughly £6,000–7,000. Add storage and the saving rises sharply — that is the whole argument for a battery.
Payback on panels alone is commonly twelve to fourteen years at current rates. Add a battery and the annual saving can rise by half again, but so does the capital cost, so payback does not shorten as much as people expect — it is the resilience and the tariff flexibility that improve. Anyone quoting you a five-year payback on a domestic system is doing something to the assumptions that they have not shown you.
What a battery actually changes
A battery does not generate anything. It moves electricity through time — and that is worth more than it sounds.
The same electricity, worth nearly four times as much
Storage catches the midday surplus you would otherwise have sold at 7p and hands it back at seven in the evening, displacing units you would have bought at 26p. Nothing extra is generated. The units simply arrive when they are worth something.
Typical effectSelf-consumption rises from around 30% to around 75% on a 13.5 kWh battery in a family home.
Storage takes the midday surplus you would have exported at 7p and gives it back to you in the evening, displacing units you would have bought at 26p. A 13.5 kWh battery typically lifts self-consumption from around 30% to around 75%.
On a time-of-use tariff you can charge the battery overnight at the off-peak rate and run the house from it through the expensive part of the day — even in winter when the panels do little. This works with no panels at all.
Only with the right hardware. Backup during an outage needs a changeover device fitted at the consumer unit; a battery on its own will shut down with the grid. Ask specifically for this if it matters to you — it is an add-on, not a default.
Domestic batteries carry ten-year warranties, typically to around 70% of original capacity. Budget for a replacement somewhere beyond year twelve when you compare against a boiler or a car.
A battery larger than your daily evening demand simply sits partly empty. Beyond about 13 kWh, most households see diminishing returns unless they run an EV or a heat pump.
Tesla Powerwall, SolaX and SolarEdge — how we choose
We are approved installers for all three, which means we have no reason to push one over another. They suit different houses.
| Tesla Powerwall 3 | SolaX Triple Power | SolarEdge Home | |
|---|---|---|---|
| Usable capacity | 13.5 kWh | 5.8 kWh per module, stackable | 9.7 kWh, stackable |
| Inverter | Built in — fewer boxes on the wall | Separate hybrid inverter | Separate, with per-panel optimisers |
| Best when | High evening demand, EV, wants one clean unit and the best app | Budget matters, or you want to start small and add modules later | The roof is shaded or faces several directions |
| Watch out for | Physically large and heavy — needs a sensible wall or floor | More separate components to site | Optimiser per panel adds cost on a simple roof |
| Warranty | 10 years | 10 years | 10 years |
“We fit all three, so there is nothing in it for us either way. A shaded roof points to SolarEdge, a simple south-facing roof with heavy evening use points to Powerwall, and a tight budget points to SolaX — because you can start at 5.8 kWh and stack another module on in two years.”
ArcticNord engineering teamPut plainly: per-panel optimisation is what stops one shaded panel dragging down a whole string, which is the entire case for SolarEdge. The integrated inverter and the tariff control in the app are the case for Powerwall. Modular capacity you can add to later is the case for SolaX. The roof and the evening usage decide it, not the brochure.
Do you need planning permission?
For most houses in England, no. Solar panels on a dwelling are usually permitted development. The exceptions are specific and worth checking before you get attached to the idea.
Two measurements decide it on an ordinary house
Panels must sit no more than 200 mm proud of the roof plane, and no part of the array may stand higher than the highest part of the roof, excluding the chimney. Meet both on a standard pitched roof and you are almost always in permitted development.
Where it changesConservation areas, listed buildings, flat roofs, ground mounts and any street carrying an Article 4 direction.
Usually fine
A pitched roof on an ordinary house, where the panels sit no more than 200 mm proud of the roof plane and no higher than the highest part of the roof, excluding the chimney.
Check first
Conservation areas and World Heritage sites — panels generally must not go on a wall or roof slope that fronts a highway. Flat roofs and ground mounts have their own limits.
Consent required
Listed buildings need listed building consent regardless of where the panels go. Refusal is common on principal elevations, and much less common on a rear slope or an outbuilding.
Rules differ in Scotland, Wales and Northern Ireland, and individual councils apply Article 4 directions that can remove permitted development rights street by street. We check this as part of the survey rather than leaving it with you — but if you are in a conservation area it is worth a call to your planning department before you go far.
The DNO application — G98 and G99
Every grid-connected system has to be notified to the Distribution Network Operator. Which form, and whether you can install first, depends on inverter size.
One threshold decides whether you wait
Under 3.68 kW per phase you fit first and notify within 28 days. Over it, approval has to be granted before anyone starts, and the DNO can take up to 45 working days to give it. Batteries with their own inverter count towards the total.
In practiceA larger array plus a Powerwall will usually put you into G99 territory. Build the wait into your plans rather than discovering it in week three.
Fit first, notify within 28 days. Straightforward, and covers a large share of domestic installs. No waiting.
Approval must be granted before installation, and the DNO can take up to 45 working days. Plan for it. Batteries with their own inverter count towards this.
This is the single most common cause of a delayed solar install, and the one homeowners are least warned about. We file the application either way and it is included in our pricing — but if a quote you are comparing does not mention DNO at all, ask why.
MCS certification and getting paid for export
This is the paperwork that decides whether you can sell your surplus.
The Smart Export Guarantee obliges larger suppliers to pay for exported electricity, but they will only sign you up with an MCS certificate for the installation. An uncertified install can still power your house — it just cannot be paid for its surplus.
SEG tariffs range from a few pence to the high teens per kWh depending on supplier and whether you take their import tariff too. It is worth shopping around; you do not have to export to your import supplier.
Qualifying energy-saving materials, including panels and batteries, currently carry no VAT on supply and installation. The relief is scheduled to end on 31 March 2027, after which the rate is expected to return to 5%.
Ask for the MCS certification number and check it on the MCS register. Ask whether the workmanship guarantee is insurance-backed. Both take two minutes and both are frequently glossed over.
The MCS certificate, DNO notification and electrical certificate are what a buyer’s solicitor will ask for when you sell the house. Losing them is expensive to fix later.
Solar, heat pump or air conditioning — which first?
We install all three, so this is not a pitch for one of them. They solve different problems and the order matters.
Solar & battery
Reduces the cost of electricity you already use. Best first move if your bills are high and your roof is decent. Does nothing for heating on its own.
Air source heat pump
Replaces gas heating with electric. Increases your electricity demand substantially — which is exactly why it pairs well with solar and storage fitted at the same time.
Air conditioning
A modern heat-pump air conditioner both cools in summer and heats efficiently in shoulder seasons. Its summer cooling load lines up almost perfectly with peak solar generation.
If you are considering more than one, get them designed together. A heat pump fitted after a solar array is often sized against the wrong assumptions, and a battery specified before you knew a heat pump was coming is usually too small.
Questions we get asked
How many solar panels do I need?+
It is set by roof space and usage rather than a rule of thumb. Smaller homes typically take six to ten panels, larger homes ten to fourteen, and homes with an EV or heat pump often more. At 450 W a panel, ten panels is about 4.5 kWp and roughly 4,000 kWh a year on a good roof.
Do solar panels work in winter, or when it is cloudy?+
Yes, but much less. Panels respond to daylight rather than heat, so they produce on overcast days — typically 10–25% of a bright day. December output is roughly a fifth of June output in the UK. Any annual figure you are quoted already averages this in.
Will panels damage my roof?+
Not if the roof was sound to begin with and the mounting is done properly. Panels are fixed to rails bolted to the rafters, with the tile or slate cut and weatherproofed around the bracket. If your roof is near the end of its life, replace it first — taking an array off and refitting it later costs more than the difference.
Can I add a battery to solar panels I already have?+
Usually yes. If your existing inverter is not a hybrid, an AC-coupled battery is fitted alongside it, which works with almost any array. It costs a little more than doing both at once and may need a fresh DNO notification.
Is a battery worth it without solar panels?+
It can be, if you are on a time-of-use tariff. You charge overnight at the off-peak rate and run the house from it during the expensive hours. The saving is smaller than a full solar and battery system but the capital cost is lower and it works all year, including December.
What happens when the power cuts out?+
By default the system shuts down — grid-tied inverters must disconnect so they cannot backfeed a network engineers may be working on. Backup during an outage needs additional switching hardware. Tell us at survey if this matters and we will specify for it.
Do I have to clean them?+
Rarely, on a pitched roof in the UK — rain does most of it. Shallow pitches, heavy tree cover or a lot of bird traffic are the exceptions. We fit bird protection to the panel edges as standard, because nesting underneath an array is the most common cause of lost output we see.
How long does an installation take?+
Two days for most domestic systems, occasionally three for a complex roof or a larger battery. Scaffolding goes up the day before and comes down within about 48 hours afterwards.
What if my roof faces the wrong way?+
East-west arrays lose only around 13% against due south and spread generation across morning and evening, which often suits a working household better. A mostly north-facing roof is a genuine problem and we will tell you that rather than sell you a compromised system.
Still not sure? Ask us the awkward question
Send your annual kWh figure and a rough description of the roof. We’ll tell you what’s realistic — including when the answer is “not yet” or “not this roof”.
What happens next
You’ll get an indicative system size, yield and saving based on your actual usage. If the numbers don’t stack up we say so in that reply, rather than booking a survey to tell you in person.