Self-Consumption: How Much of Your Own Generation You Actually Use

Solar panels on a roof do not automatically power the home beneath them in the way many people imagine. During the middle of a bright day a typical house generates far more electricity than it can use, and the surplus flows out to the grid. The share that the home keeps for itself is the self-consumption rate, and it is the single number that best answers the question every solar household asks: how much of this is actually cutting my bill?

The official definition is precise. Self-consumption is "the amount of solar electricity generated by a domestic solar PV system which is subsequently consumed within the property and not exported to the distribution network"¹. It can be quoted in kWh or as a percentage of total generation¹. Without storage, independent guidance puts the typical share at 30 to 50%; with a battery, official guidance reports the figure rising to 70 to 80%².

The proportion of generated solar power you use yourself

A solar PV system converts sunlight into electricity that can be used in the home¹. But generation and use do not line up. Panels produce most of their power between late morning and mid-afternoon, while household demand peaks in the evening and early morning. Whatever the home consumes at the moment of generation is self-consumed; whatever is left over is exported, and whatever the home draws when the panels are idle is imported.

The self-consumption rate is therefore a measure of fit between your generation and your life, not just a property of the equipment. Two identical houses with identical panels can have very different rates if one is occupied all day with washing machines and dishwashers running, and the other is empty from eight until six. This is why the rate matters more than raw generation figures when working out what solar actually saves: imported electricity is what you pay your supplier for, and every self-consumed kWh is a kWh you do not buy.

The concept sits alongside the self-sufficiency ratio, which measures the share of total demand met by generation. Self-consumption looks from the other end: of what the panels made, how much did the home keep? Both figures rise when generation and demand are better matched, and both are central to measuring household energy independence.

Working out your self-consumption rate

The calculation itself is simple: the solar electricity consumed within the property, divided by the total solar PV generation, expressed as a percentage¹. If a system generates 4,000 kWh in a year and the home uses 1,200 kWh of it as it is produced, the self-consumption rate is 30%.

The complication is that most homes do not meter self-consumed solar directly. The MCS method for estimating it therefore works from annual electricity consumption, annual PV generation and occupancy pattern, for domestic buildings where total annual consumption is between 1,500 kWh and 6,000 kWh per year¹. The estimate is drawn from the average self-consumption of a sample of domestic properties with similar occupancies, consumption and systems¹. Two worked examples from the MCS guidance show how occupancy drives the result:

Two things stand out. The home occupied all day consumes less overall but still self-consumes only 29%, because its generation is large relative to its use. The home occupied half the day self-consumes a larger share, 39%, because its generation is small relative to a heavy demand. The rate is capped in MCS estimates: "the self-consumption cannot exceed 95% of the total annual generation"¹.

There is a historical benchmark worth knowing. Under the old Feed-in Tariff scheme, it was simply assumed that a domestic property with PV would, on average, self-consume 50% of the electricity generated⁶. That 50% assumption was a scheme convention rather than a measurement, and real-world rates without storage often fall below it.

Information installers should provide before purchase

Because self-consumption drives the savings a household actually experiences, MCS rules require it to be estimated and disclosed. The self-consumption must be communicated in both estimated annual kWh and as a percentage of solar PV electricity consumed, in writing, and clearly stating whether the figure is with or without storage⁶. The current MCS standard for solar PV installations includes a dedicated assessment field for "Expected solar PV self-consumption (with EESS)", so a storage-equipped system has its own estimate⁷.

Installers using the MCS method must also give a specific statement with the estimate:

That wording matters to anyone comparing quotes. The estimate is a baseline figure for the home as occupied, before any extra measures. A diverter that sends surplus solar to an immersion heater, or an electric vehicle charged from the panels, would push the real rate above the written estimate, while a change in occupancy, someone retiring or starting to work from home, would change it in either direction. The occupancy tables behind the method distinguish homes that are out during the day from homes occupied half the day, so the estimate is only as good as the occupancy information given to the installer⁶.

Usual rates: roughly 30 to 50% with no battery, 70 to 80% with storage

The headline figures are consistent across official and independent guidance. A parliamentary research briefing reports Great British Energy's position that adding a battery to a solar installation increases self-consumption from 30 to 40% to 70 to 80%². Independent guidance for consumers gives a slightly wider band: without a battery a household might use only 30 to 50% of what is generated, and adding one can lift that to 80% or more³.

The gap between those two sets of figures is not a contradiction so much as a difference of framing: the official figure describes the change a battery typically makes, while the independent figure describes the range of outcomes across homes. What both agree on is the direction and the scale. A battery roughly doubles the share of generation the home keeps, because it moves surplus afternoon electricity into the evening instead of exporting it. The detail behind this is covered in how much a battery increases self-consumption.

For a household deciding whether storage is worth adding, the practical reading is this: the without-battery rate depends heavily on when the home uses electricity, and a home that is empty all day will sit at the bottom of the 30 to 50% band. The with-battery rate is far less sensitive to occupancy, because the battery absorbs surplus regardless of whether anyone is home. That is why the battery question, not the panel question, is usually the decisive one for self-consumption.

Battery control and running your home on solar after dark

A home battery stores the excess electricity the panels generate, or charges when the tariff is cheap, and the stored energy is then used at night or when prices are high⁸. Independent guidance describes the same arrangement from the household's side: store the extra energy created during the day, then use it at times when the system is generating less, like at night⁹. Installers describe it the same way, as enabling residents to store electricity generated during the day and use it at night¹⁰.

Modern battery systems do more than passively hold charge. Where a battery is paired with a time-of-use tariff, the system charges when electricity is cheap and discharges when the expensive period begins, and this happens automatically: charging stops when the battery is full, and it discharges when the next cheap tariff period ends⁸. This means the battery is working for the household on two fronts, capturing solar that would otherwise be exported, and arbitraging the tariff by buying low and using high.

Control settings shape the result. A household can reserve capacity in the battery for expected evening use, or let the system follow dynamic tariff prices. A solar battery can also increase savings further by storing the sun's energy to power a heat pump later in the day¹¹, which turns daylight into evening space heating. The trade-off is set out plainly in the comparison of a solar diverter versus a battery: a battery stores electricity itself, while a diverter can only convert surplus into heat.

Energy management systems and higher self-consumption

An energy management system (EMS) is the layer of control that decides, moment by moment, where electricity goes: to the home, to the battery, to a vehicle, or to the grid. Its purpose, as the certification body Flexi-Orb puts it for storage systems, is "a way of increasing your self-consumption and reducing your reliance on the grid"¹². The mechanism is matching: an EMS watches generation and demand and shifts flexible loads, battery charging, water heating, vehicle charging, into the hours when the panels are producing.

The regulatory backdrop is moving in the same direction. Parliament has provided for regulations requiring energy smart appliances to meet requirements on cyber security, data privacy, interoperability and grid stability¹³, with secondary legislation expected. In practice this means the appliances an EMS coordinates are being brought within a common framework, which should make it easier to combine equipment from different makers over the life of a system.

The maker myenergi, which sells such systems, claims the main benefit is that "you will be almost entirely self-sufficient"¹⁴. That is a manufacturer's statement and should be read as such: an EMS raises self-consumption by using energy better, but it cannot create energy the panels have not generated, and a home with no storage still exports its afternoon surplus. Council-backed schemes reflect the more modest reality, allowing households to register to have battery storage added to existing solar panels to maximise the benefits of the system¹⁵, which is an upgrade path rather than a transformation.

Maintenance expectations are modest but real. Guidance on solar systems states that "the maintenance of the solar system should be conducted by either a licenced electrician or the installer at least once a year"¹⁶, and an annual check is the natural moment to confirm the EMS settings still match the household's routine and tariff.

The limits of self-consumption

The limits deserve as firm a statement as the benefits. The most important one concerns power cuts. Typically, solar panels cannot power a home during a power cut, unless the home is off the grid or has additional equipment⁹. The reason is safety: solar panels automatically switch off during a power cut, because exporting electricity onto the network would endanger engineers working on the lines, and they usually restart on their own once power returns¹⁷. Plug-in solar panels behave the same way, being designed to switch off if there is a power cut¹⁸. The mechanism is explained in islanding and anti-islanding.

The equipment itself should come to no harm: guidance for low-carbon technologies states that equipment, including solar panels, heat pumps, EV chargers and batteries, "should not be damaged and will be ready to use again once power is restored"¹⁷. But a household that has invested in generation and storage still loses the lot during an outage unless it has paid for the additional equipment that allows the system to run disconnected.

The second limit is seasonal. Self-consumption is a fair-weather friend in one sense: in summer a well-matched system can run the home almost entirely on solar, but in winter generation falls while demand rises, and the home leans back on imports. The pattern is described in the winter gap between generation and demand. The third limit is the export itself: surplus generation sent to the grid is sold, not used, and export payments are a supplier matter outside the household's control, which is why the self-consumed share is the part of a solar system a household actually owns outright.

How roof type, orientation and shading affect generation

Self-consumption is a percentage, but the absolute amount it applies to depends on how much the roof can produce. Panels generate the most electricity when they face south, because they capture as much sunlight as possible through the day¹⁹. An east or west-facing roof will produce 15% less energy, and a north-facing roof around 30% less²⁰. Shading bites harder still: a roof that is more than 80% shaded can reduce output by as much as 50%²⁰.

Orientation guidance for roof-mounted systems generally looks for a southeast to southwest facing roof receiving direct sunlight for the main part of the day²¹. The number of panels a roof can carry is also constrained by practical factors: the roof shape, skylights, shading from nearby buildings or trees, local planning or conservation area requirements, and local grid capacity and export limits¹⁹.

For self-consumption specifically, orientation has a subtle effect worth noting. An east-facing array produces more in the morning, when a home's demand is rising, and a west-facing array more in the late afternoon and evening. A purely south-facing array peaks at midday, which is exactly when many homes need least. Households weighing this can look at sizing generation and storage for a self-sufficient home, where orientation is treated as part of the match between generation and demand rather than a matter of maximum output alone.

The cost of a solar PV installation

The most widely quoted figure is around £6,100 for a typical domestic installation of around 3.5 kWp, a figure given by the London Borough of Hammersmith and Fulham⁴, by Which?⁵, by Energy Saving Trust²² and by NICEIC²³. Larger systems cost more: Energy Saving Trust notes that domestic systems are generally around 4.5 kWp and cost around £7,600²⁴, and Confused.com gives a range of £6,100 to £11,000 depending on the size of the property²⁵.

At the small end, plug-in solar panel systems cost from around £450 to install¹⁸, though their output and their self-consumption contribution are correspondingly small. The Which ? costed example, a ten-panel system priced at £7,400 as of 1 June 2025, also gives a sense of the annual benefit: £460 per year in total for a London home with an east-facing, modestly shaded roof²⁷. Battery storage is an additional cost on top of the panels, and the full picture of what independence costs is set out in the cost of energy independence for a UK household.

Rooftop solar usually pays back in 10 to 13 years

Payback figures cluster tightly. Council guidance states that solar panels usually pay for themselves in 10 to 12 years⁴. Which ? gives a slightly wider band, between 10 and 13 years for a typical rooftop system to pay for itself through bill savings⁵, and its costed comparison puts rooftop break-even at 10.9 to 12.2 years²⁸. The Which ? London example works out at 16 years and 1 month on its own figures²⁷, a reminder that payback stretches when the roof is not ideal or the tariff and export terms are unfavourable.

Plug-in panels break even much faster, at 3.6 to 7.1 years²⁸, because the upfront cost is a fraction of a rooftop installation. The comparison between the two approaches is set out in plug-in solar panels versus rooftop systems, and the trade-off is capacity: a fast payback on a small system buys a small reduction in imports.

Two things move payback either way. Self-consumption is one of them: the more generation the home uses itself, the more each kWh is worth, since it displaces bought electricity rather than being exported at a lower rate. Independent guidance frames this as locking in a portion of energy costs at 0p per kWh for the next 25 years³, which is the effective cost of electricity the panels have already paid for. The other is the annual benefit itself, which varies with location, roof and tariff, as the £460 per year London example shows²⁷.

Self-consumption and your energy independence

A high self-consumption rate is the working definition of energy independence in miniature: generation the home owns, meeting demand the home controls, with the grid as a residual backstop rather than a daily necessity. The maker myenergi claims a self-consumption system leaves users "almost entirely self-sufficient"¹⁴, and while that is a manufacturer's characterisation, the direction is real. A household that self-consumes 70 to 80% of its generation² buys a correspondingly small share of its electricity from a supplier, and the self-consumed portion is, in effect, priced at 0p per kWh for the life of the system³.

What remains is worth naming plainly. The grid connection remains, both as the destination for exported surplus and as the source of the electricity the home still imports, above all in winter. The supplier relationship remains for the imported share and for any export payments. The tariff relationship deepens rather than disappears with a battery, since cheap-period charging depends on the supplier's pricing⁸. And the control layer, if it runs through a manufacturer's app and cloud, creates a dependence of its own, which is weighed in local control versus the manufacturer's cloud and in who owns your home energy data.

None of this makes self-consumption a poor goal. It makes it an honest one: the rate measures how far a household has moved from buying all of its electricity to making most of it, and every point of that rate is energy the home produced, kept and used on its own terms.