Quick Summary (TL;DR)
A home battery does not generate electricity: it moves energy between times, at a cost. To calculate its return, compare the bills for the same home and solar installation with and without the battery. Credit the battery only with the extra value it creates after conversion losses, foregone export revenue, tariffs, degradation, standby consumption and any maintenance. A solar array’s generation savings are not automatically battery savings.
For a transparent starting calculation, assume a battery supplies 7 kWh to the house on 250 days a year, with 90% round-trip efficiency, a 30p/kWh avoided import price and 10p/kWh foregone solar export payment. The illustrative extra annual saving is about £331 before degradation, operating costs or finance charges. A hypothetical £5,500 installed battery would have a simple first-year-rate payback of about 16.6 years — not a promise that it will ever recover that cost. Better tariff spreads, higher useful throughput or lower installed costs can change the conclusion; so can a high export tariff, winter underutilisation and shorter-than-expected lifespan.
The right question: how much does the battery add?
Battery marketing often combines solar production, self-consumption, bill savings and blackout protection into one reassuring number. Those are distinct outcomes. If a household already saves money by consuming rooftop solar directly, installing storage does not create those daytime savings again. Similarly, energy shifted from a cheap overnight rate to a peak period should be valued at the price difference after storage losses, not at the full peak price.
The most useful comparison is an incremental one. Run two scenarios with identical weather, household demand, solar generation, tariffs and equipment outside the battery package:
- Without storage: household uses direct solar, imports when necessary and exports the remainder.
- With storage: household still uses direct solar, but the battery can absorb suitable surplus or buy cheap electricity and discharge later, subject to its controls, power limits and reserve.
Subtract the first bill from the second. Subtract any new standing costs, battery subscription or service costs. Then compare the net incremental cash flow with the fully installed battery price. Keep blackout resilience as a separately stated benefit, unless you have a defensible financial estimate.
| Common headline | What it actually measures | Why it can mislead |
|---|---|---|
| Solar plus battery reduces import by 60% | Combined effect of photovoltaic generation and storage | Direct solar may account for most of the reduction |
| 10 kWh battery saves 10 kWh every day | Nominal or usable capacity, not proven daily discharge | Solar surplus, demand, reserve and seasonality constrain cycling |
| Peak rate is 30p/kWh | Avoided import cost in a chosen interval | Export revenue or cheap charging cost must be deducted |
| Battery is 95% efficient | Could be cell, DC or test-condition efficiency | Financial calculation needs whole-system energy in versus energy out |
| Warranty is 10 years | A limited contractual promise | Does not mean free lifetime maintenance or zero capacity loss |
| Backup is worth £1,000 per year | Subjective willingness to pay or avoided losses | Do not insert an arbitrary cash value into payback |
Start with a realistic installed cost, not the battery-module price
The purchase price in a web advert is seldom the amount that appears on the installer invoice. An existing solar inverter might be compatible with a new AC-coupled battery, require a supported hybrid-inverter replacement, or need extra metering to control charging and grid export correctly. Backup capability is frequently a separate project: isolation equipment, a gateway or changeover arrangement, an essential-loads board, commissioning and local approvals.
Include installed hardware, labour, taxes where applicable and commissioning, as well as any ongoing platform or tariff requirement. Ask whether the quote includes a dedicated energy meterAliExpress price, current transformers, communication gateway, DC disconnects, additional consumer-unit work, fire-location requirements, export-control configuration and a usable manufacturer’s warranty. Quote requirements vary by country and installation.
| Line item | Include in capital expenditure? | Typical omission to check |
|---|---|---|
| Battery modules and battery management | Yes | Is capacity nominal, usable or reserved? |
| Battery inverter or hybrid inverter | Yes if incremental | Is an existing solar inverter being replaced? |
| Meter, CTs and communications | Yes | Are the specified models inverter-approved? |
| Safety and electrical works | Yes | Enclosures, isolation, protection, earthing, design and testing |
| Backup gateway and critical-load circuits | Only if buying backup | Many grid-tied batteries cannot power the home in an outage without extra equipment |
| Installer design, labour and commissioning | Yes | Grid registration and export-limiting configuration |
| Subscription, extended warranty and servicing | Operating cost or explicit upfront item | Recurring costs must not disappear from the model |
| Future inverter/battery replacement | Scenario cost when likely | Manufacturer warranty and component lifetimes are different |
As a real-world reference rather than a shopping quotation, the UK’s Energy Saving Trust listed a roughly £4,600 cost for a 5 kWh battery system in its October 2026 guidance, with much wider costs across sizes and installations. Treat that as background context, not as the price of the device you are evaluating. Always obtain current itemised local quotes.
Four numbers determine most of the energy arbitrage
Before building a spreadsheet, collect four inputs: energy actually discharged into useful household loads; number of useful cycling days; whole-system round-trip efficiency; and the price difference between the source and destination of energy. A battery with high usable capacity but insufficient evening demand may have worse economics than a smaller one. A larger battery also need not be worse if it serves a heat pump or dynamic tariff; the crucial variable is measured useful throughput.
Use the following sign convention for a simple annual estimate. E_out is AC energy delivered from battery to household loads over the year. η is round-trip efficiency from the energy source boundary to the delivered-load boundary. The required input energy is E_in = E_out / η. Let P_avoided be the import price the discharged battery energy genuinely avoids, and P_source the cost or forgone revenue per kWh used to charge it. Then:
Gross incremental annual value = E_out × P_avoided − (E_out ÷ η) × P_source.
Net annual cash benefit = gross incremental value − added battery running costs − any charging/discharging fees.
For solar charging, P_source is normally the export payment you would otherwise receive, provided all the charged electricity really was exportable. For grid charging, it is the actual off-peak import tariff plus applicable variable charges, not zero. Import standing charges normally cancel in a before/after comparison unless storage changes the tariff or fixed fee. Model changing prices by tariff period instead of using one average when possible.
Worked example: 7 kWh delivered over 250 days
Suppose a household can discharge 7 kWh on 250 days after direct solar use, yielding E_out = 1,750 kWh/year. Assume 90% round-trip efficiency measured at the whole battery system’s AC boundary. That means 1,944.4 kWh must enter the battery, and approximately 194.4 kWh is lost to conversion and storage. Take an avoided import price of 30p/kWh and foregone solar export of 10p/kWh.
| Calculation | Expression | Illustrative value |
|---|---|---|
| Useful annual discharge | 7 × 250 | 1,750 kWh |
| Annual battery charge input | 1,750 ÷ 0.90 | 1,944.4 kWh |
| Avoided grid imports | 1,750 × £0.30 | £525.00 |
| Export revenue sacrificed | 1,944.4 × £0.10 | £194.44 |
| Gross incremental saving | £525.00 − £194.44 | £330.56/year |
| Hypothetical installed cost | Given assumption | £5,500 |
| Simple payback at unchanged first-year gross saving | £5,500 ÷ £330.56 | 16.6 years |
The numbers above are scenario inputs, not tariffs or product performance measured by esp32AliExpress price.co.uk. They assume the battery can use its planned 250 days, no lost opportunity to fill before evening, no tariff restrictions and no extra service cost. They also ignore degradation, financing and discounting. This is why the resulting 16.6 years is a starting warning signal, not an investment forecast.
Solar self-consumption versus charging from the grid
There are two potentially valuable ways to use the battery, and they are not additive unless the kWh are disjoint. A solar-charged kWh usually trades away export income to avoid a later import. A grid-charged kWh buys electricity cheaply for delivery during expensive hours. Some systems also support paid export or grid services, but those need a separate revenue model and eligibility check.
| Charging mode | Source-energy price | Discharged energy value | Additional questions |
|---|---|---|---|
| Solar surplus → evening home use | Foregone export rate | Avoided evening import rate | Would the energy otherwise be exported or curtailed? |
| Cheap overnight grid → peak home use | Actual overnight unit rate | Avoided peak import rate | Are grid charging and the chosen tariff allowed? |
| Battery → paid grid export | Charging cost plus losses | Export settlement received | Is dispatch supported, contractually allowed and reliably metered? |
| Solar surplus → EV/hot water directly | Foregone export value | Avoided energy purchase for that load | Would direct consumption be more efficient than cycling through a battery? |
| Battery kept charged for outages | Opportunity cost of energy and unavailable cycling | Resilience rather than routine bill reduction | How much state-of-charge reserve is required? |
Do not double-count the same 1,750 kWh as both solar self-consumption savings and overnight arbitrage. A seasonal or hourly model should decide which source charges the battery on each day, how much it later delivers, and the counterfactual bill without storage. Also remember that a high solar export tariff can reverse the decision to charge: exporting today may be financially preferable to storing energy for later.
Price sensitivity: the same battery can have four different returns
Keep 1,750 kWh of annual discharge, 90% efficiency and zero added running costs. These deliberately simplified cases show how sensitive the cash flow is to the difference between import value and energy source cost.
| Avoided import price | Charging energy / sacrificed export value | Gross annual incremental value | Simple payback on £5,500 |
|---|---|---|---|
| 30p/kWh | 5p/kWh | £427.78 | 12.9 years |
| 30p/kWh | 10p/kWh | £330.56 | 16.6 years |
| 30p/kWh | 15p/kWh | £233.33 | 23.6 years |
| 20p/kWh | 15p/kWh | £58.33 | 94.3 years |
The last result is not a serious prediction that a battery can run for 94 years. It simply flags an uneconomic tariff pairing at the stated cost and throughput. A lower-cost installation or a dynamic tariff may produce a radically different result. Where a UK Smart Export Guarantee is available, the supplier chooses its rate and conditions; there is no universal export rate. Ofgem’s published report also shows substantial variation between tied and untied export products. For readers in other markets, enter the applicable local settlement, self-consumption or net-billing rules.
Cycle life, calendar ageing and usable capacity
Battery degradation has two broad sources: calendar ageing, even when lightly used, and cycle ageing, influenced by energy throughput, charge/discharge rates, state-of-charge window and temperature. The battery-management system protects cells but cannot eliminate ageing. A warranty often promises minimum retained capacity under specified conditions, rather than original output for the warranty’s entire duration.
A pack advertised as 10 kWh nominal might expose less usable energy because the manufacturer reserves some capacity. Separately, the owner may maintain a 20% minimum state of charge for blackout resilience. Those numbers are not interchangeable: choose the quoted usable capacity first, then apply any user-reserved share of that usable range if the product lets you do so. Do not subtract manufacturer reserve a second time.
Illustration: a 10 kWh usable system with a user-imposed 20% reserve would have at most about 8 kWh available for routine discharge before inverter limits, discharge-efficiency adjustments and ageing. If usable capacity later declines by 20%, the corresponding upper bound becomes about 6.4 kWh for the same proportional reserve. Real results depend on the system’s definition of reserve, BMS calibration and whether the load needs more power than the inverter can supply.
| Ageing assumption | Example model input | Modelling caution |
|---|---|---|
| Year-one usable energy | 10 kWh | Must match the manufacturer’s usable AC/DC boundary |
| First-year useful discharge | 1,750 kWh | Constrained by demand, solar surplus, tariffs and reserve |
| Annual capacity decay | 2% per year, illustrative only | Not a quoted universal LFP degradation rate |
| 10-year capacity factor | 0.98^9 ≈ 0.834 in year 10 |
Actual ageing is rarely exactly linear or exponential |
| Cycle-throughput limit | Use the warranty’s documented units | MWh discharged and equivalent full cycles are not identical to calendar age |
| Replacement year and cost | Scenario-specific | Do not infer automatic free replacement at warranty expiry |
The 2025 National Laboratory of the Rockies (formerly NREL) Residential Battery Storage model uses 85% as a representative round-trip efficiency in its research scenario. That is a modelling assumption, not a test result for a particular Powerwall, Victron or Enphase product. For another reference, Victron’s Lithium Smart Battery documentation quotes 92% round-trip efficiency for the battery model and particular cycle-life figures; that is not a blanket promise for an entire inverter-plus-battery installation.
Tesla’s January 2025 European Powerwall limited warranty illustrates why region and use matter: it specifies a ten-year term and, for named European countries including the UK, an 80% ten-year capacity-retention threshold for specified self-consumption, time-based and backup applications. Other listed applications have an aggregate throughput condition. Check the exact effective warranty and your country rather than repeating an internet claim of ‘ten years, unlimited cycles’ without its qualifications.
Model the cash flow year by year, not just cost ÷ savings
Simple payback can be a useful filter, but it cannot tell whether a ten-year battery will earn back a fourteen-year first-year-rate payback. For a genuinely useful decision, create a model with one row for each year, preferably with hourly electricity and demand data beneath it. Include annual net savings, battery capacity and any required replacement or service costs. If you have a discount rate, calculate the net present value (NPV) of those future cash flows and compare competing systems at the same analysis horizon.
An accessible annual spreadsheet can start with the following fields:
| Column | Spreadsheet variable | Example calculation |
|---|---|---|
| A | Year | 1 through 15 |
| B | Retained usable capacity factor | =(1-$B$2)^(A2-1) for constant assumed annual fade in an illustrative sheet |
| C | Useful discharge (kWh) | =MIN(annual demand-shift limit, annual available charging, first-year throughput × B2) |
| D | Avoided imports (£) | =C2 × avoided import rate |
| E | Battery input (kWh) | =C2 / round_trip_efficiency |
| F | Charging opportunity cost (£) | =E2 × weighted charging source price |
| G | Added operating cost (£) | Monitoring subscription, service or other verified cost |
| H | Net annual incremental benefit (£) | =D2-E2*source_price-G2 |
| I | Discounted benefit (£) | =H2/(1+discount_rate)^A2 |
For column C, do not cap useful throughput using capacity alone: a battery can cycle more than once per day on some tariffs, or fail to complete even a fraction of a daily cycle on winter days. The final model should draw potential charging and demand from time-stamped measurements. The simplified row-level spreadsheet is an approximation for preliminary screening.
For example, retain the £330.56 first-year gross incremental benefit and assume a purely illustrative 2% annual decline in that benefit, with all prices frozen. The undiscounted 10-year sum is about £3,024, still considerably below the assumed £5,500 installed cost. Discounting, fixed operating costs or an expensive component replacement makes the case weaker; more useful cycles, cheaper installation or improved tariff spreads makes it stronger. These are not manufacturer forecasts or estimates for a particular home.
Financial metrics worth displaying together
| Metric | Meaning | When useful |
|---|---|---|
| Incremental annual cash benefit | Bill difference with minus without battery | Best first-year reality check |
| Simple payback | Installed cost ÷ first-year annual benefit | Quick screen; weak when performance changes |
| Discounted payback | First year when cumulative discounted benefits recover cost | Compares money received now versus later |
| NPV | Present value of benefits minus all incremental costs | Compare investments over a common horizon |
| Battery lifetime cash balance | Sum of realised savings minus cash expenditure | Practical lifetime check; ignores time value unless discounted |
| Effective delivered-energy cost | Incremental cost / lifetime useful delivered kWh | Helpful if defined at consistent AC load boundary |
| Outage duration supported | Critical-load energy / usable reserved energy | Resilience metric, not automatically cash return |
A nominal battery module’s advertised price per kWh is not equivalent to whole-system levelised cost of storage. The full installed cost, usable lifetime throughput, conversion losses, replacement costs and discount rate all matter. It is possible for a battery to have positive bill savings and still have a negative lifetime financial return.
Backup value: important but easy to manipulate
For some readers, the financial decision is secondary to being able to power refrigeration, networking, lights or a medical appliance during a blackout. Backup value is real to the household, but there is no single defensible £/kWh figure that turns it into universal annual income.
Assess backup separately: how often does the grid fail, for how long, and what power is genuinely available? A system rated 5 kW continuous cannot reliably support simultaneous loads requiring 8 kW just because it stores 10 kWh. A 10 kWh nominal battery might be able to supply roughly a 500 W critical load for substantially less than 20 hours after usable capacity, inverter losses, reserve and surge constraints. Proper grid isolation and approved backup equipment are essential; a normal grid-following solar inverter usually cannot run a house during an outage without a suitable backup architecture.
| Backup question | Why it matters |
|---|---|
| Does the quote include backup switchgear and compliant islanding? | Battery ownership does not guarantee blackout power |
| Which circuits stay live? | Whole-home versus essential-load wiring changes cost and duration |
| What is the inverter’s continuous and surge rating? | Motors and heat pumps may exceed power limits |
| What battery reserve will be kept? | Resilience reduces energy available for daily arbitrage |
| Can solar recharge in a prolonged outage? | Vendor- and topology-dependent; test the documented operating mode |
| How will the system be inspected and maintained? | Electrical safety and inverter firmware matter over the battery life |
If resilience is the purpose, label its value as a separate household benefit or a clearly explained estimated avoided-loss scenario. Do not quietly add £300 per year to a bill-savings column to force an attractive payback.
Choosing capacity for the household rather than the brochure
Start with measured demand. A household that regularly consumes 6 kWh after sunset has a natural reason to explore a system near that usable shift requirement, provided it can charge it. A 20 kWh battery bought for a 3 kWh evening shortfall will often remain underused. In contrast, an EV, electric heating or a heat pump can create high night-time demand and make dynamic rates more relevant — but an EV charging overnight directly at the cheapest tariff may already achieve the same saving without cycling the stationary battery.
Look at at least four weeks of representative winter data and a representative summer period, ideally a full year from half-hourly or better meter readings. Forecast solar production conservatively and note whether your panels export enough during the months you would like to charge. Grid-charging eligibility may vary by tariff and battery product; export remuneration for energy originally drawn from the grid may face special restrictions.
| Home profile | Capacity and strategy question | Main ROI risk |
|---|---|---|
| Small house, strong export tariff | Can storage beat selling solar surplus? | High opportunity cost of lost export |
| Home with heat pump | Does winter demand coincide with cheap tariff windows? | Not enough cheap energy or insufficient charge power |
| Home with solar but little evening demand | Will the battery actually discharge daily? | Oversizing and capacity underutilisation |
| Dynamic tariff household | Can vendor controls safely respond to prices? | Software, subscription and tariff changes |
| Home requiring critical backup | What capacity must remain reserved? | Less daily cycling and higher installation cost |
| Three-phase home | Does the proposed system meter and support phases as intended? | Wrong phase accounting or unsupported backup behaviour |
Compare batteries by usable delivered energy, continuous output, supported inverter and meter combinations, minimum state-of-charge policy, warranty, installer support, blackout mode and transparent running costs. For architecture choices, our companion articles cover ESP32 Modbus energy metering, Energy dashboard troubleshooting, and energy measurement methods. Those existing published guides help with capturing the data, but none independently makes a battery profitable.
Use Home Assistant to measure the actual outcome
Home Assistant can help build a defensible before-and-after record, especially if your grid meter, solar inverter and battery integration expose correctly defined energy totals. Configure distinct lifetime import, export, solar generation, battery charge and battery discharge entities where supported. The Energy dashboard helps visualise flows but should not be treated as a substitute for the electricity supplier’s settlement meter. Tariff estimation must respect actual billing windows, standing charges, export conditions and taxes.
For calculations, use cumulative kWh counters or energy statistics with appropriate units and metadata. Instantaneous W or kW measurements are not interchangeable with accumulated kWh. Check signed power conventions and whether the battery reports DC cell energy or AC output, because a spreadsheet that mixes these boundaries will produce impossible apparent efficiency. Avoid counting both the inverter’s synthetic ‘load’ sensor and an independently metered household-load sensor as separate consumption.
A practical commissioning and data-quality checklist:
- Confirm the utility meter’s cumulative import and export totals over at least one billing period.
- Verify CT directions and three-phase aggregation, including periods of simultaneous phase import/export if your meter records them.
- Make solar and battery entities consistent: input versus output and AC versus DC measurement boundaries must be documented.
- Check counter behaviour after inverter reboots or integration updates; a reset can falsely inflate energy statistics.
- Compare estimated self-consumption with meter flows on a typical sunny day and an evening discharge.
- Confirm whether cheap-grid charging is permitted and correctly allocated to purchased energy rather than ‘free solar’.
- Export monthly or half-hourly statistics for your ROI model. Record tariff changes and export settlement conditions as dated inputs.
- Re-run the calculation after three, six and twelve months; adjust useful cycles and efficiency to observed values instead of leaving optimistic assumptions unchanged.
A smart energy-management system may improve dispatch, but its control software should not bypass battery BMS limits, protective equipment, inverter export settings or approved electrical installation arrangements. Manufacturer cloud/app support, local Modbus readouts and actual write-control permissions are different capabilities.
Sensitivity analysis: what to stress-test before paying a deposit
Make a low, central and optimistic case. Change one variable at a time before combining them. The most consequential assumptions tend to be installed capex, annual useful discharge, effective round-trip efficiency, import/export price spread, lifespan and residual usable capacity. A conservative model also explores tariff-policy changes and any need to replace an inverter midway through the battery’s life.
| Input | Conservative case | Central illustration | Optimistic case |
|---|---|---|---|
| Annual useful discharge | 1,000 kWh | 1,750 kWh | 2,500 kWh |
| Whole-system efficiency | 85% | 90% | 93% |
| Avoided import price | 22p/kWh | 30p/kWh | 33p/kWh |
| Foregone export / source rate | 15p/kWh | 10p/kWh | 5p/kWh |
| Installed cost | £6,500 | £5,500 | £4,000 |
| Operating or replacement cost | Higher, explicitly modelled | Itemised | Lower, verified |
| Warranty/life | Exact country and use case | Exact product document | Never assume indefinite operation |
These numbers are illustrative sensitivity inputs, not current battery quotes or a predictive UK tariff forecast. Do not interpret the optimistic case as an expected result. For a reader outside Britain, replace pounds, export arrangements, tax and electrical regulations with locally applicable values; the underlying incremental-energy accounting remains the same.
The UK Energy Saving Trust’s July 2026 analysis of household technology and time-of-use tariff combinations reached a practical conclusion: pairing batteries, solar and low-carbon heating with a suitable tariff can reduce energy bills, but additional battery savings often do not recover the installed cost in the system’s expected lifetime, particularly where export tariffs are favourable. This is consistent with evaluating the marginal cash flow, rather than using generic claims about maximum self-consumption.
Buying recommendation: when to proceed, defer or prioritise something else
Proceed to detailed quotations when you have a documented large tariff spread or frequent exportable solar surplus, sufficient daily load at an expensive rate, measured energy flows, a supported inverter and meter pairing, and an acceptable lifetime financial model. If backup is essential, specify it as a separate project and acknowledge the resilience premium.
Wait or buy something else first when the tariff spread is small, export payments are attractive, consumption is mostly daytime, the battery would be oversized, or the installation requires costly replacement of otherwise serviceable equipment. More solar capacity, load shifting, an EV charging schedule, better insulation, a heat-pump control strategy or a compliant energy meterAliExpress price may offer better first returns. A battery is not automatically the next rational purchase after solar panels.
Get at least two or three itemised quotations, request the actual battery and inverter warranty PDFs for your region, and demand a written estimate with all assumptions shown: annual delivered battery energy, energy losses, reserve, discharge limits, tariff dates, expected solar export lost, subscriptions, backup hardware and replacement policy. If an installer cannot distinguish battery-only incremental savings from total solar-plus-battery savings, treat the quotation with caution.
Frequently asked questions
Does a home battery pay for itself in ten years?
Sometimes, but not universally. A ten-year warranty is not evidence of ten-year payback. Installed price, usable annual throughput, energy-price spread and ageing determine whether it does. In the worked example here, simple payback already exceeds ten years before modelling degradation.
Is electricity stored from solar really free?
Not necessarily. If you could sell surplus solar electricity, charging the battery sacrifices export revenue. The right calculation compares the later avoided import bill with the export income surrendered and storage losses. If solar would otherwise be curtailed with no compensation, its marginal financial source cost may be close to zero, subject to system constraints.
Is LFP always better for long-term return?
Lithium iron phosphate is widely used in stationary storage and often offers favourable thermal and cycling characteristics, but return depends on the complete supported system: usable capacity, AC efficiency, power, warranty, price, temperature management, installation and software. Chemistry alone does not determine ROI.
Should I charge my battery at night and export solar during the day?
It can make sense where the tariff differential and battery controls support it. Compare the delivered cost of grid-charged energy, including losses, with the import prices it avoids, and compare solar self-consumption with the available export payments. Confirm any supplier restrictions on battery charging and export settlement.
How much is blackout backup worth?
That depends on what an outage would cost your household and how reliable the power supplyAliExpress price is. Determine required critical loads and blackout duration first. Include the extra installed backup equipment and energy reserve; keep this benefit separate from routine energy-bill ROI unless a transparent avoided-loss estimate is justified.
Can Home Assistant prove my savings?
It can provide useful evidence if measurements are complete and calibrated against billing data. It cannot reconstruct an accurate ‘without battery’ counterfactual simply by counting battery discharge: you still need charging costs, foregone export, losses and time-of-use prices. Reconcile smart-meter and inverter boundaries first.
Official sources and further reading
- Energy Saving Trust — Battery storage (updated October 2026): home battery operation, costs, typical lifespan and sizing.
- Energy Saving Trust — Technology and tariff combinations (July 2026): household bill savings and the effect of time-of-use tariffs on financial outcomes.
- National Laboratory of the Rockies — 2025 Residential Battery Storage ATB: research-model assumptions including efficiency and lifetime costs.
- Tesla — European Powerwall warranty (January 2025): retained capacity, application and throughput conditions; confirm current revision and local region.
- Victron — Lithium Battery Smart technical data: battery-level efficiency and cycle-life test conditions.
- Ofgem — Smart Export Guarantee: why actual export compensation is tariff-specific.
- Home Assistant — Home energy management: monitored grid, solar and battery energy.
