Why Is My Electric Bill So High With Solar Panels?
If your bill still feels high with solar, it’s almost always one of seven things: the system is underproducing, you use most electricity after sunset, your export tariff pays peanuts compared with your import rate, your household consumption has grown since the install, it’s simply winter, your standing charges have gone up, or the system was always undersized for what you actually use. The fix is rarely “more panels” — it’s usually shifting usage into daylight, adding a battery, or switching to a tariff that rewards solar properly.
You spent the money on solar expecting the bill to drop. Most months it has — but you still get a four-figure-or-near-it annual bill and you can’t quite work out why. After fitting, servicing and diagnosing hundreds of UK systems we see the same handful of causes over and over. This guide walks through all seven, in the order we’d check them on a real site visit.
In this guide
Some bill is normal — here’s why
Unless you’re fully off-grid (rare in the UK), some electricity bill is always going to exist. Three pieces won’t go away no matter how good your panels are:
- Standing charge. A daily fixed fee for the grid connection, typically 50–65p/day — that’s £180–240 a year before you use a single unit.
- Evening and night import. Panels generate in daylight; you use lights, cooking, EV charging and heat pumps after sunset.
- Winter import. December to February output is a fraction of summer, and heating demand peaks in the same months — a double squeeze.
The job isn’t to get the bill to zero. It’s to get the variable part — the imported units — as low as your kit and usage pattern realistically allow. Below are the seven things that prevent that.
1. The system is producing less than it should
This is the first thing to rule out. Open your inverter app or monitoring portal and compare this month against the same month last year. If kWh has dropped 15%+ with no obvious explanation, something has changed on the roof.
- Dirt and bird mess. A solid year of UK weather plus pigeons living under your panels can drop output 5–25%. An annual clean usually pays for itself.
- New shading. Trees grow; neighbours build extensions. A shadow on one cell can knock out a whole string — we’ve seen 30%+ losses from a single aerial cable.
- Inverter fault. Inverters are the most common failure point. A failing inverter rarely dies cleanly — it limps along at 60–80% output for months before anyone notices.
- Panel degradation. Quality modern panels degrade at under 0.5%/year. If you’re losing 2–3%/year there’s a real fault, not just age.
2. You use most of your electricity after the sun goes down
This is the single biggest reason we hear “my bill is still high.” Your panels are working perfectly — but at 7pm, when the family’s home, the oven’s on, the EV’s charging and the heat pump’s running, your panels are doing nothing. You pay full import rate (often 25–30p/kWh) for every unit, while the surplus you exported earlier got paid 5–15p.
- Shift usage into daylight. Run the dishwasher and washing machine on timers between 11am and 3pm. Set the EV to charge during the day if it’s home, or on a cheap overnight window if it isn’t.
- Add battery storage. Stores the daytime surplus and discharges it across the 4–7pm peak. For most UK family homes a 16kWh Fogstar or equivalent pays back in 6–8 years and keeps paying off long after.
3. Your export tariff is paying you less than your import costs
The UK doesn’t do net metering. Every kWh you export earns the export rate; every kWh you import costs the import rate — and they’re wildly different numbers.
| Tariff scenario | Typical import | Typical export | Spread you lose |
|---|---|---|---|
| Default supplier, basic SEG | 27p/kWh | 5p/kWh | 22p/kWh |
| Octopus Flux | peak ~38p, off-peak ~14p | peak ~28p, off-peak ~5p | varies |
| Octopus Agile + Predbat | half-hourly, often 2–15p | Outgoing Agile 12–25p | often inverted (export > import) |
If you’re on a 5p SEG and you exported 2,000 kWh last summer, that’s £100. The same 2,000 kWh used in your home would have been worth £540 at 27p import. Either use more of what you generate, or switch to a smarter tariff — our Octopus Agile + solar guide covers what Agile + Predbat actually returns.
4. Your household uses more electricity than when the system was sized
Solar systems are sized against your historical consumption at survey time. Three things commonly push consumption up after install:
- An EV. Adds 1,500–4,000 kWh/year depending on mileage. A 4kWp system sized for a no-EV home is visibly undersized 18 months after an EV joins the household.
- A heat pump. Air-source heat pumps roughly triple winter electric load. A system sized for gas-heating consumption won’t cover it.
- Working from home. A permanent home office — laptop, monitors and heating in one room all day — adds 500–1,200 kWh/year.
If your daytime consumption has genuinely grown, you may need more panels — not more battery. See our battery sizing guide for how to tell the difference.
5. It’s winter (or you’re comparing the wrong months)
A 4kWp UK system might generate 600 kWh in May and 80 kWh in December — an 8× ratio. If you’re looking at a January bill and despairing, compare it against last January, not against the £30 bill you got in June.
| Period | Share of annual yield | Typical kWh (3,600 kWh/yr system) |
|---|---|---|
| Dec – Feb | 10–15% | 360–540 kWh total |
| Mar – May | 25–30% | 900–1,080 kWh |
| Jun – Aug | 35–40% | 1,260–1,440 kWh |
| Sep – Nov | 20–25% | 720–900 kWh |
6. Standing charges and rising unit rates have moved against you
Even with the same import volume, your bill in 2026 is higher than it was in 2022. UK standing charges have risen sharply and unit rates have followed. If you’re comparing a current bill to a pre-solar bill from three or four years ago, the rate change alone can hide a real consumption reduction.
The honest comparison is in kWh, not pounds. If your imported units are clearly down year-on-year, solar is doing its job — the rate environment is what’s pulling the headline number back up.
7. The system was just too small from day one
This is the hardest conversation, and one we sometimes have with customers another installer originally fitted. The symptoms:
- You export almost nothing — the panels are flat-out, the home eats every kWh, and there’s nothing left for a battery to absorb.
- Daytime imports remain meaningful even on sunny days.
- Your consumption has clearly grown since install (EV, heat pump, family change) and no upgrade was added at the time.
Adding panels is more involved than retrofitting a battery — a new DNO notification, a possible inverter swap, scaffolding — but if the issue is “not enough generation,” a battery alone won’t solve it.
Not sure which of the seven it is for you?
Spectrum can pull your last 12 months of monitoring and bills and tell you within 24 hours which fix actually moves your numbers. The assessment is free.
Speak to Our TeamShould you add a battery or more panels?
This is the decision most “still high” bills come down to. A 10-minute monitoring pull usually settles it:
✓ A battery is the answer if…
- You generate more in the day than you use, and export a healthy surplus
- Most of your consumption is after 5pm
- You’re on (or can switch to) a peak/off-peak tariff
- Daytime imports are already low on sunny days
✗ You need more panels first if…
- You export almost nothing — the home eats every kWh
- Daytime imports stay high even when it’s sunny
- You’ve added an EV or heat pump since the install
- A battery would simply sit empty
The 8-step diagnostic we use on a site visit
Step 1: Compare generation year-on-year
Pull the last 12 months of inverter generation against the year prior. Flag any month with a 15%+ drop.
Step 2: Check for faults
Open the inverter app for active error codes or fault history.
Step 3: Inspect for shading
Trees, new aerials, bird mess. Time of day matters — midday shadows are the killers.
Step 4: Confirm the panels are clean
Pollen, lichen and pigeon traffic add up over a year.
Step 5: Split day vs evening usage
Pull a 7-day half-hourly smart-meter export. If more than 60% of usage is after 5pm, you have a timing problem, not a generation problem.
Step 6: Check the tariff spread
Standing charge, import rate, export rate — calculate the gap you’re losing on every exported unit.
Step 7: Tally anything added since install
EV, heat pump, hot tub, home office — add up the new kWh load.
Step 8: Benchmark the yield
Compare actual annual yield against system size × the UK rule-of-thumb (typically 850–1,100 kWh per kWp). Below 800/kWp means there’s a fault to find.
FAQs
Why do I still pay an electricity bill if I have solar panels?
Unless you’re fully off-grid with a large battery, you’ll always have some import. Panels generate in daylight; you use power overnight and on dull winter days. Plus every UK supplier charges a daily standing charge for the grid connection itself — that part of the bill solar can’t touch.
Why are my solar panels not saving me money?
In our experience the four most common reasons are: the system is underproducing (shading, dirt, an inverter fault); you use most electricity after sunset so you’re still importing peak-rate power; your export tariff pays much less than your import rate; or your household consumption has grown (EV, heat pump, working from home) since the system was sized.
Can solar panels stop working without me noticing?
Yes. Inverter faults, partial shading and slow degradation can knock 20–40% off output with no visible damage. Always check your monitoring app’s daily kWh against the same month last year. If you don’t have monitoring, that’s the first thing to fix.
Will a battery actually lower my bill?
If you generate enough in the day but use most of your power in the evening, yes — a battery shifts that solar into the peak-rate window where it offsets the most expensive imports. If your panels barely cover the daytime, a battery alone won’t help; you’d need to add panels too.
Is it normal for my winter electricity bill to be higher with solar?
Completely normal. A UK domestic system typically produces only 10–20% of its annual yield across December, January and February combined — and heating demand is highest in the same months. Compare your winter import this year against last year, not against your sunny May bill.
Should I add more panels or install a battery?
If your panels already generate more than you can use during the day, you need a battery — the surplus is being exported cheap and bought back expensive. If your panels rarely cover even your daytime load, you need more panels first; a battery would just stay empty. A monitoring pull tells you which in about 10 minutes.
Related reading
- Octopus Agile + solar: 2026 guide to maximum savings
- Best solar battery for Octopus Agile in 2026
- How much solar battery storage do I need?
- What is Predbat? Solar battery optimisation explained
For service and inspection support see our domestic solar overview.
Get a real diagnosis, not a guess
Spectrum has been fitting and servicing solar across the East Midlands since 2011. We’ll review your monitoring data and bills and tell you exactly which of the seven causes is dragging your savings down — and whether the fix is free, £100, or worth a battery quote.
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