Octopus Zero Bills is the simpler choice when you are buying an eligible home and want predictable home-energy costs. DIY solar is the better fit when you want to choose the equipment, keep control of the battery and accept the work and risk involved. They are not like-for-like purchases: one is a conditional energy tariff attached to an approved whole-home system, while the other is equipment you specify and own.
That distinction matters more than a headline payback figure. Octopus does not publish the portion of a new home’s price attributable to its Zero Bills equipment, and a retrofit depends on the house, specification, installer quote and finance. Any table claiming an immediate payback for Zero Bills, or one universal payback for DIY, would pretend those missing inputs do not exist.
| Decision | Octopus Zero Bills | DIY solar and battery |
|---|---|---|
| What you buy | An eligible home or approved upgrade, plus a conditional 5 or 10-year tariff | Equipment and installation that you specify |
| Energy bill | £0 for covered home energy while you meet the applicable terms: the 5-year tariff has a 10,000kWh consumption allowance and a 4,000kWh net-import threshold; the 10-year tariff has a 4,000kWh net-import allowance | Reduced, not guaranteed; the result follows generation, consumption and tariff rates |
| Battery control | Octopus programmes approved equipment and receives demand-response rights | You choose the settings, subject to equipment, electrical and grid constraints |
| EV charging | Charged separately through an approved charger on Intelligent Octopus Go | Paid from your tariff or supplied by your solar and battery |
| Main financial unknown | Equipment cost within the home price, or the retrofit quote and finance | Your parts, labour, compliance, maintenance and changing tariff value |
Which option is better for you?
Choose Zero Bills if the property has already been approved, you are comfortable with Octopus managing the equipment, and you value a defined period without covered home-energy charges. Before you attach a value to that benefit, ask the developer what comparable homes without the package cost and read the tariff terms that will apply to your property.
Choose DIY if you want to decide the system size, component brands and battery schedule. The possible saving comes partly from doing work and procurement yourself. You also take responsibility for design, safe installation, DNO requirements, commissioning, warranties, maintenance and finding a suitable import or export tariff.
There is a third option that is more relevant to many homeowners: buy a conventional professionally installed solar, battery and heat-pump system. That keeps equipment ownership separate from the Zero Bills tariff and avoids pretending that the only alternatives are a new-build package or hands-on DIY.
What does Octopus Zero Bills actually cover?
As checked on 10 July 2026, Octopus publishes separate 5-year and 10-year Zero Bills terms. Both cover electricity import and export with no standing charge, provided the home and its equipment remain eligible. Their allowances are not identical. The 5-year terms provide a maximum 10,000kWh electricity-consumption Fair Use Allowance in each 12-month period, but charge electricity above 4,000kWh net import at the Flexible Octopus rate. The 10-year terms define the Fair Use Allowance as a maximum 4,000kWh net import in each 12-month period. Net import means grid electricity imported minus electricity exported, while consumption is the electricity the home uses.
For both tariffs, Octopus can charge net import above 4,000kWh at the Flexible Octopus rate and reserves the right to remove a household after it exceeds that net-import threshold for two years or more. On the 5-year tariff, this is separate from the 10,000kWh consumption allowance. This is why I would call Zero Bills a conditional £0 home-energy tariff, not unlimited free energy.
EV electricity is outside the 4,000kWh net-import level and is billed separately at Intelligent Octopus Go rates. The terms require an approved charger connected to Intelligent Octopus Go. A household can therefore have a £0 bill for covered home energy and still pay to charge its car.
The home must keep its approved heat pump, solar PV, battery, smart meters, Octopus Home Mini and internet-connected equipment working. The published terms also require the home to have no gas meter, or for the customer to agree to remove it. Check the exact contract offered with the property because eligibility and equipment specifications belong to the approved home, not to this article.
How should you compare the real costs?
Start with the amount you must pay, not the value of the tariff in isolation. For a new build, ask for the complete property price, mortgage terms, service or maintenance obligations, equipment warranties and the price of a genuinely comparable home. I cannot call the Zero Bills equipment free or calculate its payback when its contribution to the purchase price is not disclosed.
Retrofit is even more property-specific. Octopus announced a Suffolk upgrade trial in February 2025 for suitable existing homes, initially aimed at customers in newer homes who already had a heat pump. The associated Suffolk loan offered up to £15,000 over seven years at 0% interest, but Suffolk County Council now says the available loan funding is fully allocated. Do not build a 2026 retrofit calculation on that finance unless the council confirms a new application round and you qualify.
A heat-pump quote also needs the grant treated correctly. In England and Wales, the Boiler Upgrade Scheme currently provides £7,500 towards an eligible air-to-water or ground-source heat pump and £2,500 towards an eligible residential air-to-air system. From 21 July 2026, qualifying off-gas-grid properties replacing oil or LPG can receive £9,000 for an eligible air-to-water or ground-source system. The scheme is installer-led and does not make every property or installation eligible.
For DIY, build a household model from your own quote and energy data. Include parts, scaffolding or access equipment, electrician and testing costs, DNO work, expected solar generation, battery losses, maintenance, finance and the tariff rates you can actually obtain. Keep import savings, export income and battery tariff arbitrage as separate lines. Each can change independently.
What control do you give Octopus?
The current terms require you to leave the heat pump, inverter and battery settings as Octopus remotely programmes them. You can set heating preferences, but the equipment must remain connected and you must not alter the advanced settings. In exchange, Octopus manages the system so it can deliver the tariff.
The contract also gives Octopus exclusive rights to enter demand-response contracts using the home’s low-carbon technology while you remain on Zero Bills. You cannot join another export tariff at the same time. That is a commercial exchange: Octopus gets control and flexibility from the equipment, while you receive the covered energy tariff.
With your own system, you can schedule the battery around your consumption, solar forecast and tariff. That freedom is useful, but it is not automatically profitable. Import and export rates change, battery cycling has losses, and an automation error can buy or sell electricity at the wrong time. Control has value only if you are willing to operate the system carefully.
What has my DIY system actually delivered?
My 7.15kWp solar array, 15kWh Fogstar battery and 3.6kW Sunsynk inverter cost about £9,000. Over the first three years I measured about £4,000 of savings. That is my household result from a budget-focused system I installed and operate, not an estimate for your house and not a like-for-like price for an Octopus-approved package.
The result came with work that a Zero Bills buyer avoids. I researched and sourced the components, mounted and wired the solar equipment, configured the inverter and battery, built automations and arranged the regulated electrical work and grid process. A professional quote should not be marked down simply because it costs more than my parts-heavy DIY route. It includes labour, business overhead, system responsibility and a different support arrangement.
I prefer direct control of my battery, so DIY still suits me. Someone who wants predictable bills and no interest in operating an energy system can rationally prefer Zero Bills. The comparison turns on what each household is buying, not on proving that one route wins for everyone.
What should you ask before committing?
- Is this exact property approved? Ask for the applicable 5 or 10-year tariff terms and the approved equipment schedule.
- Which annual limits apply? Confirm the consumption allowance, net-import threshold and how any excess charge will appear on the bill.
- What happens when the fixed term ends? Price the home on the assumption that an ordinary tariff will apply afterwards.
- Who pays for maintenance and replacement? Read the heat pump, battery, inverter and solar warranties rather than assuming the tariff covers every failure.
- How is EV charging treated? Include the separate charger, eligibility and Intelligent Octopus Go costs if you have or expect to buy an EV.
- What finance is actually available? Compare the total amount repayable, not only the monthly payment or interest rate.
- What would the conventional alternative cost? Obtain a professional solar, battery and heat-pump quote as well as any DIY parts list.
The bottom line
Zero Bills offers something DIY cannot guarantee: covered home energy at £0 for a defined term when an approved home stays within the contract. DIY offers something Zero Bills deliberately takes over: component choice and operating control.
If you are comparing homes, value Zero Bills using the exact property price and contract. If you are upgrading an existing home, get a current eligibility decision, an itemised installation quote and confirmed finance before counting any savings. If you are considering DIY, model your own consumption and accept that the result depends on safe execution and changing tariffs. Those checks produce a useful decision; a generic payback table does not.
