One Year After Solar: Still Paying £0 for Energy? Here's What Actually Happened
The KMM customer check-in video that's clocked 1,730+ views in months. Real numbers from a UK customer 12 months after install — what worked, what they'd change.
The video everyone wants to see
If you've researched solar PV in the UK in the last six months, the question that keeps coming up is the same: do the numbers actually hold up after the install? Brochure economics and reality have a habit of diverging. KMM filmed a 12-month customer check-in to answer the question directly. The video has 1,730+ views in a few months — the highest-engagement piece on the KMM channel — because it's the answer most installers refuse to publish.
What the customer started with
The featured customer is a UK family home in a rural-edge village withacross the UK. Pre-install electricity spend was around £2,400/year on a 28p/kWh fixed-rate tariff with an existing electric vehicle being charged from the grid most evenings. The roof had two pitched faces — one south-east, one north-west — and no significant shading from neighbouring trees or buildings.
The KMM system installed
- Panels: 5.6 kWp DC on the south-east face, 13 × 430W tier-1 modules
- Inverter: 5kW hybrid (SolaX X1)
- Battery: 9.5 kWh LFP (GivEnergy)
- EV charger: Zappi v2.1 7kW with solar-divert mode
- Tariff move: from a 28p fixed to Intelligent Octopus Go (7.5p overnight + 15p export)
The 12-month actual numbers (not modelled — actual)
What the customer said on camera
Direct paraphrase: "Honestly, I half expected to find the maths was wrong somewhere. It hasn't been. I drive an EV, I run the dishwasher and washing machine on automatic timers during the day, and the bill just stopped being a thing I think about. I haven't 'tried' to save energy — I just got out of its way."
Three things this 12-month checkpoint tells us
- The modelled numbers held up. Generation came in 4% above model, savings came in 3% above. KMM's quoting model is calibrated against actual UK weather data, not the panel manufacturer's optimistic test-conditions number.
- The EV is the multiplier. Without the EV daytime load, self-consumption would have been ~55% rather than 78%. EV ownership compounds solar economics — the more discretionary load you have, the better the system performs.
- The tariff change matters as much as the hardware. Half of the £2,019/year saving comes from moving to Intelligent Octopus Go (7.5p overnight vs 28p fixed). Installers who don't help their customers move tariff leave money on the table.
What we'd do differently with hindsight
One thing: a slightly larger battery. The customer's overnight import on Octopus Go averages 12.4 kWh — meaningfully more than the 9.5 kWh battery can soak up. A 13.5 kWh battery would have captured an additional ~£90/year by displacing more daytime peak grid use. That's £900 across the decade — comfortably more than the £600 extra battery cost.
How to apply this to your own quote
Three things to ask any installer (us or anyone else) before signing a contract:
- What annual generation are you modelling, and what's it based on? (Look for "PVGIS" or "Helios 3D" answers, not "manufacturer estimates")
- What self-consumption ratio? (Above 60% with battery on a typical home, above 75% with EV)
- Will you help me switch tariff at commissioning? (If they say "no, you sort that" — assume you'll lose 30-50% of the modelled saving)
Once you've asked those three questions, book a fully funded survey or run a quick payback estimate for your roof.
Request a Fully Funded Electrical & Structural Survey
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