A home battery can work extremely well with a heat pump.
But the battery does not necessarily need to run the heat pump all day.
The better question is:
What part of the heat pump’s electricity use do you actually want to shift?
That might be:
- expensive evening electricity
- daytime solar into evening heating
- peak grid demand
- cheap overnight electricity
- backup heating
A home battery can support a heat pump without needing to power the entire heating system on its own.
And the battery should be sized around the job it is actually being asked to do.
Size the battery around the electricity you want to move, not the total electricity the heat pump uses all day.
Can a Home Battery Run a Heat Pump?
Yes, potentially.
A heat pump is an electrical load, so a home battery can supply some or all of that demand if:
- the battery inverter can provide enough power
- the battery contains enough stored energy
- the electrical system is configured to allow it
But that does not mean the battery needs to make the heat pump electrically independent from the grid.
A battery can still create significant value by:
- reducing expensive grid import
- supporting peak demand
- shifting solar energy
- helping during a power cut
- coordinating with a smart tariff
The battery does not need to do everything to make a meaningful difference.
An 8 kW Heat Pump Does Not Usually Draw 8 kW of Electricity
One of the biggest misunderstandings is confusing heat output with electrical input.
An 8 kW heat pump is normally rated to deliver around 8 kW of heat under defined operating conditions.
It does not necessarily consume 8 kW of electricity.
For example, at a COP of 4: 2 kW electrical input → approximately 8 kW heat output.
This is only an illustrative example because real performance changes with operating conditions.
But the principle is important:
The number on the heat pump normally describes heat output, not the electrical power the battery has to supply.
COP Changes the Relationship Between Electricity and Heat
COP stands for Coefficient of Performance.
A COP of 4 means that, in simplified terms, 1 kWh of electricity → around 4 kWh of heat.
This is why a heat pump can make much more useful heat from a stored electrical kWh than a direct resistance heater.
One electrical kWh can become several kWh of useful heat when the heat pump is operating efficiently.
A Heat Pump Is Not a Fixed Electrical Load
The electrical demand of a heat pump changes throughout the day and throughout the year.
It can be affected by:
- outdoor temperature
- required flow temperature
- compressor speed
- hot-water production
- defrost
- auxiliary heaters
So one fixed electrical input figure is not enough to design the battery around.
A heat pump is not a fixed electrical load. Its power demand changes with the conditions and the job it is doing.
Battery Design Should Follow the Real Demand Profile
It is tempting to design around the heat-pump model number, rated thermal output or one brochure COP figure.
But that can miss how the system actually behaves.
A better battery design looks at:
- normal heating demand
- cold-weather electrical input
- hot-water cycles
- auxiliary loads
- peak-tariff periods
- household loads operating at the same time
Battery design should follow the heat pump’s electrical demand profile, not its model badge.
Winter Is the Real Test
Cold weather is where the interaction between heat pump and battery becomes most demanding.
As outdoor temperature falls:
- the home loses heat faster
- the heat pump runs for longer
- electrical input may rise
- solar generation is seasonally lower
That creates a double challenge.
The battery is being asked to support more heating demand at exactly the time solar replenishment is often weakest.
The hardest time for a battery to support a heat pump is often the same time the home needs the heat pump most.
Battery Runtime Is Seasonal
A battery that feels large during summer can behave very differently during winter.
In summer, household demand may mainly include appliances, cooking, lighting and electronics.
In winter, continuous heating demand is added.
That can dramatically reduce runtime.
A battery that feels large in summer can feel much smaller once the heating season starts.
And: battery runtime is seasonal because household demand is seasonal.
A Battery Cannot Move Summer Solar Into Winter
Battery storage is very useful for moving energy over hours, overnight or part of a day.
It is not seasonal storage.
A home battery can charge from midday solar and help supply the heat pump later that evening.
But it cannot store large amounts of excess August generation for use during a cold January week.
A battery can move solar from lunchtime to evening heating. It cannot move August into January.
Battery kWh and Battery kW Are Different Problems
- Battery Capacity — kWh
- How much electrical energy is stored. It mainly affects how long the battery can help.
- Battery Power — kW
- How quickly the stored energy can be delivered. It affects how much load the battery can support at once.
When looking at a heat pump, the battery needs enough energy and enough power.
These are not the same thing.
A Full Battery Can Still Be Too Power-Limited
Example
Heat-pump electrical input 2.5 kW, other household demand 1.5 kW. Total demand 4 kW. Battery discharge limit 3 kW.
Even if the battery contains plenty of stored energy, the battery supplies 3 kW and the grid still supplies 1 kW.
A battery can have enough stored energy but still not have enough power to cover the heat pump and the rest of the home together.
Auxiliary Heaters Are the Hidden Electrical Load
The heat-pump compressor is not always the largest electrical load in the heating system.
A system may also contain:
- immersion heater
- backup heater
- DHW booster
- emergency electric heater
These can be several kilowatts each.
The compressor may not be the largest electrical load in the heat-pump system.
Worked Example: Backup Heater Changes Everything
Example
Normal operation — heat pump compressor 2.5 kW, other home demand 2 kW, battery inverter 5 kW. Total 4.5 kW. The battery can potentially cover that demand.
Now a 6 kW auxiliary heater switches on. Potential total demand becomes 10.5 kW.
The same battery behaves completely differently.
A battery designed around normal heat-pump operation may behave very differently when an auxiliary heater switches on.
Immersion Heaters Need Their Own Strategy
An immersion heater is a resistance heater.
In simple terms: 1 kWh electricity → approximately 1 kWh heat.
A heat pump operating efficiently can create several kWh of useful heat from the same electrical input.
That means stored battery energy may often have much more heating value when used through the heat pump compressor rather than directly through an immersion.
Using stored electricity through the heat pump can produce more useful heat than sending the same electricity directly to an immersion heater.
Do Not Let Cheap-Rate Immersion Heating Drain the Battery
Imagine a cheap overnight tariff begins.
The immersion is scheduled to heat the cylinder.
At the same time, the home battery sees 3 kW of new household demand and starts discharging.
Now the home is using stored battery energy while cheap grid electricity is already available.
That may be exactly the opposite of the intended strategy.
The home battery should not automatically discharge into an immersion heater when cheap grid electricity is already available.
Daily Heat-Pump Consumption Is Not Battery Size
Suppose the heat pump uses 15 kWh of electricity per day.
That does not mean the property needs 15 kWh of battery storage.
Some of that electricity may be:
- used directly from cheap grid electricity
- supplied directly by solar
- used when electricity is already inexpensive
- shifted thermally into the building
- shifted into hot water
Daily heat-pump electricity use is not the same thing as required home-battery capacity.
Size the Battery Around the Hours You Want to Shift
Example
Heat-pump electricity over 24 hours: 15 kWh.
Heat-pump electricity between 16:00 and 19:00: 3 kWh.
Other household demand during the same period: 2 kWh.
If the goal is to avoid an expensive three-hour tariff period, the relevant energy target might be closer to 5 kWh than the full 15 kWh heating day.
Size the battery around the electricity you want to move, not the total electricity the heat pump uses all day.
Different Battery Goals Need Different Battery Sizes
- Peak-Price Avoidance
- How many kWh need to be moved across the expensive tariff period?
- Solar Shifting
- How much daytime solar needs to be stored for later heating?
- Peak Shaving
- How many kW of grid demand should the battery reduce?
- Backup Heating
- Which heating loads need to operate, and for how long?
A heat pump does not create one universal battery requirement.
There is no single battery size for a heat pump because there is no single job the battery is being asked to do.
A Heat-Pump Home Has More Than One Energy Store
- Electrical Storage
- The battery stores electricity for later use.
- Building Thermal Storage
- The home stores heat in floors, walls, furniture and building fabric.
- Hot-Water Storage
- The cylinder stores thermal energy for later use.
This is one of the most useful ways to think about the system.
Energy can be stored as electricity, room heat or hot water.
A heat-pump home can store energy electrically in the battery and thermally in the building and hot-water cylinder.
The Home Itself Can Store Heat
A property does not instantly become cold when the heat pump switches off.
Heat is stored in floors, walls, furnishings and internal structure.
A well-performing building may therefore be able to use cheap electricity slightly earlier and coast through part of a more expensive period.
With a heat pump, the home itself can become part of the energy-storage strategy.
A Hot-Water Cylinder Stores Energy Too
A cylinder is a purpose-built thermal store.
The heat pump can potentially heat the cylinder during cheap electricity periods, solar generation or low household demand.
That hot water can then be used later.
A hot-water cylinder stores energy too — just in the form of heat rather than electricity.
Sometimes Cheap Electricity Is Better Used Immediately
Imagine cheap electricity is available now.
There are two possible routes.
Route A — Grid → Battery → Heat Pump Later
Route B — Grid → Heat Pump Now → Building Stores Heat
Route B avoids battery charging losses, battery discharge losses and additional battery cycling.
If the building genuinely needs heat and can store it comfortably, direct use can make more sense.
If the heat pump can use cheap electricity at the time it is available, direct use may be better than storing it electrically first.
The Cheapest kWh May Be Better Stored as Heat
This is one of the key differences between a heat-pump home and many other electrical loads.
A cheap electrical kWh could be stored in the home battery, or used immediately to create room heat or hot water.
The best option depends on what the home will need later.
The cheapest kWh may be better stored as heat than stored as electricity.
Preheating Does Not Mean Overheating
Thermal load shifting should not mean heating the house excessively.
A sensible strategy might raise room temperature modestly before an expensive tariff period.
The building then releases some of that stored heat while the heat pump reduces its demand.
Thermal shifting works by moving heat in time, not by overheating the house.
A Heat Pump Is Flexible, But It Is Not an EV Charger
An EV can often stop charging for several hours and simply catch up later.
A heat pump is different.
Its operation affects room temperature, building thermal mass, comfort, recovery demand and efficiency.
If the heat pump is stopped for too long, the house may cool significantly.
A heat pump is flexible, but it is not infinitely deferrable.
Aggressive Tariff Avoidance Can Backfire
Imagine electricity is expensive from 16:00–19:00.
Turning the heat pump off for all three hours might appear attractive.
But if the house cools too much, the heat pump may later need to run for longer, work harder, use higher flow temperatures and recover lost room temperature.
That can reduce efficiency.
Avoiding an expensive tariff period is not useful if the heat pump has to work much harder afterwards to recover.
Weather Compensation and Tariff Optimisation Must Work Together
A well-designed heat pump usually performs best with low flow temperatures, steady operation, weather compensation and minimal unnecessary stop/start cycling.
Tariff optimisation should work around this.
It should not destroy efficient heating operation simply to avoid a few expensive half-hours.
The heating system should not be made less efficient just to make the electricity schedule look clever.
Different Homes Store Heat Differently
The flexibility available from preheating depends on the building.
Important factors include insulation, airtightness, thermal mass, floor construction, heating emitters and outdoor temperature.
A well-insulated high-mass property may stay comfortable for much longer than a lightweight or poorly insulated home.
The same heat pump can be highly flexible in one house and barely flexible in another because the building stores heat differently.
Underfloor Heating Can Offer Significant Thermal Flexibility
A screeded underfloor heating system contains a large amount of thermal mass.
The screed can warm slowly, release heat gradually and retain useful heat after the heat pump reduces output.
That can make gentle preheating particularly useful.
A screeded floor can store useful thermal energy even though it is not a dedicated heat-storage device.
Radiators Behave Differently
Radiators generally have lower thermal mass, quicker response and less stored heat after heating stops.
That does not make radiators unsuitable for smart tariffs.
It simply means the available thermal shifting may be different.
The heating emitters affect how much useful heat can be shifted in time as well as how efficiently it is delivered.
Hot Water Is Often More Flexible Than Space Heating
Space heating is constrained by comfort.
Hot-water cylinders are designed specifically to store heat.
That often makes domestic hot water easier to shift around tariffs, solar generation and grid constraints.
Hot water can often be shifted more aggressively than space heating because the cylinder is designed to store it.
Heat-Pump Hot Water and Immersion Heating Are Not the Same
The heat pump can often produce hot water at a COP greater than 1.
An immersion heater converts electricity directly into heat at close to 1:1.
There are still situations where immersion heating may be required, such as high-temperature boosts, system-specific control or backup functions.
But they should not be treated as electrically equivalent.
Do not treat heat-pump hot-water production and immersion heating as the same energy path.
Cheap Electricity Can Have Three Main Destinations
- Charge the Home Battery
- Store electricity for later.
- Heat the Building
- Store thermal energy in the property.
- Heat the Hot-Water Cylinder
- Store thermal energy in water.
Imagine a cheap tariff period has started. The electricity could be used in any of these three ways.
This is where whole-home control becomes much more important than controlling each product independently.
The best controller decides whether to store the cheap kWh as electricity, room heat or hot water.
Sometimes the Smartest Battery Strategy Is Not to Use the Battery
A battery does not need to charge or discharge simply because it can.
If electricity is cheap now, the house needs heat now and battery energy is more valuable later, then Grid → Heat Pump may be the best route.
A smart battery strategy sometimes means deliberately leaving the battery alone.
Tomorrow's Weather Can Change Tonight's Decision
Imagine tomorrow is forecast to be cold and cloudy.
It may make sense to charge the battery more overnight, prepare more hot water and retain more energy.
Now imagine tomorrow is cold but very sunny.
The system may want to leave more battery capacity available for daytime solar.
Tomorrow’s weather can change where tonight’s cheap electricity should go.
Solar Forecast and Temperature Forecast Both Matter
- Solar Forecast
- How much cheap self-generated electricity might arrive tomorrow?
- Temperature Forecast
- How much heating demand is likely?
A heat-pump home needs to consider two different forecasts.
These two forecasts can produce very different battery strategies.
Battery strategy for a heat-pump home should consider both tomorrow’s sunshine and tomorrow’s temperature.
Solar Can Run the Heat Pump Directly
When solar generation and heating demand occur together, direct solar-to-heat-pump use can be very effective.
Imagine solar electricity of 1 kWh and a heat-pump COP of 4.
In a simplified example that electrical energy could create approximately 4 kWh of useful heat.
A solar kWh used by an efficient heat pump can create several kWh of useful heat.
Solar and Heating Demand Do Not Peak Together
There is an important seasonal limitation.
Solar generation is usually strongest in spring and summer.
Space-heating demand is usually strongest in autumn and winter.
So solar can contribute to shoulder-season heating, sunny winter days and hot-water production.
But it does not remove winter grid demand.
Solar can help run a heat pump, but the sun and the heating season do not peak together.
A Battery Can Shift Solar Within the Day
Imagine solar generation is strong at lunchtime. The battery charges.
That evening, solar falls but the heat pump still needs electricity. The battery can discharge into the home and reduce grid import.
That is a realistic daily storage job.
The battery can move solar across the day, not across the seasons.
Battery Efficiency and Heat-Pump COP Work Together
Example
1 kWh electricity enters the battery. Battery round-trip efficiency 90%. Energy returned later: approximately 0.9 kWh.
Heat-pump COP 4. Useful heat: 0.9 × 4 ≈ 3.6 kWh.
Compare that with direct use: 1 kWh electricity × COP 4 ≈ 4 kWh heat.
This is simplified, but it demonstrates the principle.
The battery loses some electricity before the heat pump multiplies the remainder into heat.
COP Is Not Fixed
The previous example does not mean a heat pump always operates at COP 4.
COP can change with outdoor temperature, flow temperature, hot-water temperature and operating conditions.
That means the value of battery energy can also change.
The value of a stored battery kWh depends partly on how efficiently the heat pump can use it at that moment.
Better Heat-Pump Design Makes the Battery More Useful
A well-designed heat pump can usually operate with lower flow temperatures, appropriately sized emitters, good weather compensation and lower electrical input.
That means every battery kWh lasts longer.
The better the heat pump is designed, the further each stored battery kWh can go.
This is one of the most important links between heating design and home-energy design.
A Bigger Battery Should Not Hide Poor Heating Design
If a heat-pump system is using excessive electricity because of unnecessarily high flow temperature, poor emitter sizing, poor controls or excessive resistance heating, buying a larger battery does not solve the underlying problem.
A bigger battery should not be used to hide an inefficient heating design.
Improve the heating system first.
Then decide how much of the remaining electrical demand is worth shifting.
Our sister site
For heat loss calculations, emitter sizing, flow temperatures and heat-pump system design, see Heat Loss Hub — our sister site, run by the same team.
Real Heat-Pump Operation Includes More Than Space Heating
A proper battery design should consider normal heating, domestic hot water, defrost, auxiliary heating, and pumps and controls.
A steady-state brochure figure does not tell the whole story.
Battery design should consider real heat-pump operation, not one steady-state test point.
Charging the Battery and Running the Heat Pump Can Create a Large Grid Load
Example
Battery charging 5 kW, heat pump 3 kW, immersion 3 kW, other household loads 2 kW.
Potential import: 13 kW.
That may be completely manageable on some properties. On others, it could approach the practical import limit.
Charging the battery and running the heat pump together can create a much larger grid load than either device alone.
Better Timing Can Reduce Peak Import
The solution does not always need to be a bigger supply.
The system may instead:
- keep heat pump running
- reduce battery charge power
- move hot-water heating later
- prevent immersion operation
- shift flexible household loads
The answer to a busy electrical system is often better timing before it is a bigger grid connection.
A HEMS Can Coordinate the Heat Pump and Battery
A Home Energy Management System can potentially consider:
- room temperature
- outdoor temperature
- weather forecast
- heating demand
- hot-water state
- battery SOC
- solar generation
- solar forecast
- import tariff
- export tariff
- backup reserve
- grid import limit
It can then make decisions about battery charging, battery discharge, room preheating, hot-water timing, solar export and battery reserve.
The controller should decide what the home needs, then choose the best energy path to deliver it.
A Smart Heat Pump and a Smart Battery Still Need to Agree
It is possible to have a smart heat pump, smart battery, smart tariff and smart solar inverter and still have poor overall control.
For example the heat pump says preheat now, the battery says avoid grid import and discharge, and the tariff says cheap electricity available.
Each device may be following its own rules. The total system may still be doing something inefficient.
A smart heat pump and a smart battery still need to agree on what “smart” means.
Comfort Is the Main Constraint
Energy optimisation should not mean cold rooms, no hot water or excessive temperature swings.
The system should use the flexibility that is genuinely available while preserving comfort.
Energy optimisation should work around comfort, not ask the household to work around the optimisation.
Will a Heat Pump Run From a Battery During a Power Cut?
Possibly.
But simply having a heat pump and a home battery does not mean the heating will continue during an outage.
The installation needs the correct backup architecture.
That can include a backup-capable inverter, suitable gateway, correct electrical circuits, enough inverter power and enough battery energy.
Having a battery does not mean the heat pump will keep running during a power cut.
Backup Power and Backup Energy Are Different
- Backup Power
- Can the battery inverter supply enough kW to start and run the heat pump?
- Backup Energy
- Does the battery contain enough kWh to keep it operating for the required time?
Backup power decides whether the heat pump can run. Backup energy decides how long it can run.
Auxiliary Heaters Can Change Backup Design Completely
Important
Imagine a heat-pump compressor at 2 kW with a backup inverter of 5 kW. The compressor may be manageable.
Now a 6 kW electric heater starts. The backup inverter may no longer be able to support the system.
A heat pump may be backup-compatible while its electric heaters are not.
This is why backup design may need to prevent certain auxiliary heaters, prioritise compressor operation and restrict hot-water boosts.
Backup Heating Does Not Need to Reproduce Normal Operation
During a grid outage, the objective may simply be to maintain safe room temperatures, provide frost protection, heat important areas and preserve battery energy.
The system may not need to provide every normal heating and hot-water function.
Backup heating does not have to reproduce normal operation to keep the home safe and comfortable.
The Building Already Contains Stored Heat
A warm building contains a significant amount of thermal energy.
During a power cut, the floor, walls, furnishings, water and building fabric continue releasing heat.
That means immediate comfort depends on more than battery capacity alone.
During an outage, the heat already stored in the building can be as important as the electricity stored in the battery.
Backup Reserve Has an Opportunity Cost
Imagine a 10 kWh battery keeps 20% in reserve for outages. That leaves roughly 8 kWh available for normal energy shifting.
Increasing the reserve improves resilience. But it reduces the amount available for heating import reduction, tariff shifting and self-consumption.
Every kWh held for backup is a kWh that cannot be used to reduce heating import today.
Worked Example: Avoiding an Expensive Evening Period
Example
Heat-pump electricity between 16:00 and 19:00: 3 kWh. Other household demand: 2 kWh. Total: 5 kWh.
The heat pump may consume 15 kWh over the full day.
But if the battery's job is only to bridge that expensive three-hour period, the relevant energy requirement may be closer to 5 kWh than 15 kWh.
Daily heating consumption does not define battery size. The battery's intended job does.
Worked Example: Store Electricity or Store Heat?
Example
Cheap electricity is available 02:00–05:00. The system has three possible uses for it.
Option A — charge the battery. Store electricity for later household use.
Option B — preheat the home slightly. Use the heat pump while electricity is cheap and allow the building to carry some of that heat forward.
Option C — heat the hot-water cylinder. Store thermal energy for morning hot-water demand.
The best decision depends on current room temperature, building thermal mass, outside-temperature forecast, battery SOC, solar forecast, hot-water demand and later electricity prices.
The best destination for cheap electricity depends on what the home will need later.
Worked Example: Battery Efficiency × COP
Example
Electricity entering battery 1 kWh. Battery round-trip efficiency 90%. Electricity returned 0.9 kWh. Heat-pump COP 4. Useful heat: approximately 3.6 kWh.
Direct electricity into the heat pump at the same COP: approximately 4 kWh heat.
The battery route loses some energy. That does not make the battery route bad.
The reason for using it is that the electricity may be cheaper earlier, solar-generated earlier, or more valuable later.
Battery storage creates value by moving electricity in time, not by making the energy conversion more efficient.
Worked Example: Winter Battery Runtime
Example
Usable battery capacity 10 kWh.
Mild evening — average home demand 1 kW. Simplified runtime: about 10 hours.
Cold evening — heat pump plus household demand 4 kW. Simplified runtime: about 2.5 hours.
Real operation will vary, but the principle is clear.
The same battery can deliver very different runtime in different seasons.
What Should a Good Battery and Heat-Pump Proposal Show?
A good combined design should explain more than heat-pump model + battery size.
Useful information includes:
- heat-pump electrical input
- expected winter demand
- battery usable capacity
- battery charge power
- battery discharge power
- auxiliary heater ratings
- immersion load
- tariff strategy
- expensive-period target
- thermal preheat strategy
- hot-water timing
- solar interaction
- backup reserve
- import capacity
- backup capability
- control ownership
- HEMS integration
A battery and heat pump are not fully designed together until someone has explained how they will operate together.
Common Home Battery and Heat Pump Questions
Can a home battery run a heat pump?
Yes, potentially. The battery needs sufficient discharge power, stored energy and suitable system architecture.
Does an 8 kW heat pump need an 8 kW battery inverter?
No. The 8 kW rating usually refers to heat output rather than electrical input.
How much electricity does a heat pump actually use?
It varies with heat demand, outdoor temperature, flow temperature, COP, hot-water cycles and auxiliary loads.
Should I size the battery around daily heat-pump consumption?
Not necessarily. It is usually more useful to size the battery around the electricity you actually want to shift.
Does a heat pump mean I need a larger battery?
It can make additional battery capacity useful because the home uses more electricity, but it does not automatically mean the largest possible battery is best.
Can a battery cover the heat pump during expensive tariff periods?
Potentially. The battery needs enough usable energy and discharge power to support the heating and other household demand during that window.
Does battery power matter as much as battery capacity?
Yes. Capacity determines how much energy is stored. Power determines how much load can be supplied at once.
What happens if the heat pump's backup heater turns on?
Electrical demand can rise substantially, potentially beyond the battery inverter’s output.
Can an immersion heater drain the battery?
Yes. A 3 kW immersion can consume stored energy quickly if the battery is allowed to support it.
Should the battery power the immersion during cheap-rate periods?
Usually the control strategy should consider whether direct cheap-grid electricity would be a better energy source than stored battery energy.
Is it better to charge the battery or preheat the home?
It depends on the tariff, building thermal mass, comfort, battery SOC and future heating demand.
Can the house itself store heat?
Yes. Floors, walls and other building materials store thermal energy and can allow limited heating demand to be moved in time.
Is underfloor heating useful for tariff shifting?
Screeded underfloor heating can offer useful thermal storage because the floor has significant thermal mass.
Are radiators less flexible than underfloor heating?
Radiators generally store less heat but respond faster. Both can be used with smart control, but their flexibility characteristics differ.
Can a hot-water cylinder act as energy storage?
Yes. It stores energy as heat and can allow hot-water production to be shifted to cheaper or more favourable periods.
Is direct solar-to-heat-pump use efficient?
It can be. A heat pump can convert each electrical kWh of solar into several kWh of useful heat when operating efficiently.
Can a battery store enough summer solar for winter heating?
No. Domestic batteries are designed for short-term storage rather than seasonal storage.
Does heat-pump COP affect battery runtime?
Yes. A more efficient heat pump needs less electrical energy to produce the same amount of heat, so each stored battery kWh can go further.
Does lower flow temperature make battery storage more useful?
Potentially, because lower flow temperatures can improve heat-pump efficiency and reduce electrical demand.
Can charging the battery and running the heat pump overload the supply?
They can create a significant combined load, particularly if an immersion or auxiliary heater also operates.
Can a HEMS coordinate the heat pump and battery?
Potentially. A suitable system can coordinate battery SOC, tariffs, solar, temperatures, forecasts and hot-water demand.
Will my heat pump work from the battery in a power cut?
Only if the electrical installation and battery backup system are designed to support it.
Can backup electric heaters run from the battery?
Possibly, but their high electrical demand may exceed the backup inverter’s capability. They may need to be restricted during an outage.
How much battery reserve should I keep for heating backup?
There is no universal figure. The right reserve depends on battery capacity, desired outage duration, heating demand and other backup loads.
Should a larger battery compensate for poor heat-pump efficiency?
No. Heating-system efficiency should be improved first rather than using additional battery capacity to hide unnecessary electrical demand.
Manage Heat, Electricity and Storage Together
A heat pump and home battery can work extremely well together.
But the battery should not be treated as the only place where energy can be stored.
A heat-pump home can store energy in the home battery, the building and the hot-water cylinder.
The best strategy depends on:
- when heat is needed
- when electricity is cheap
- how much solar is available
- battery state of charge
- outside temperature
- building thermal mass
- hot-water demand
- backup requirements
A home battery can support a heat pump without needing to power the entire heating system on its own.
Size the battery around the electricity you want to move, not the total electricity the heat pump uses all day.
The cheapest kWh may be better stored as heat than stored as electricity.
A heat pump is flexible, but it is not infinitely deferrable.
The heating system should not be made less efficient just to make the electricity schedule look clever.
A battery can move solar from lunchtime to evening heating. It cannot move August into January.
The better the heat pump is designed, the further each stored battery kWh can go.
The best controller decides whether to store the cheap kWh as electricity, room heat or hot water.