Solar panels, a battery or a heat pump: which should you get first?

For most UK homes the practical order is solar panels first, then a battery, then a heat pump. Solar is the only one of the three that generates its own income stream, through the electricity it displaces and through export payments, and it is the one that makes the other two cheaper to run once they arrive. Independent guidance is direct on the point: if you already have solar panels, you can save more by using the free energy they generate to power your heat pump¹.

The order is not a rule, and it is not enforced by any scheme. Official guidance confirms that heat pumps which integrate with solar photovoltaic systems are eligible under the Boiler Upgrade Scheme, so grant funding does not force a sequence². What drives the sensible order is the shape of each technology: solar produces electricity when the sun is out, a battery moves that electricity to when it is needed, and a heat pump converts electricity into heat at a rate of up to three times the energy it consumes³.

The trade-off is cost and disruption. Independent research found that high upfront costs mean combined heat pump, solar and battery systems do not always provide the strongest financial return at current technology costs, even where the bill reductions are large⁴. That is the honest framing: the sequence matters less than whether the fabric of the home, the tariff and the electrical supply can carry all three.

What each technology does for a household

The three technologies do different jobs, and confusing them is the main reason households stall on the decision.

Solar photovoltaic panels convert sunlight directly into electricity, which can be used in your building⁷. That electricity can run anything on the circuits, including a heat pump, and it reduces how much electricity is drawn from the grid⁸. Solar thermal is a separate technology: panels that heat water rather than generate electricity. Official guidance states that solar thermal equipment can generate between 55% and 70% of a home's hot water requirements, reducing a home's carbon footprint⁶, and a Northern Ireland government guide puts the figure at up to 60 per cent of a household's domestic hot water needs over a year⁹. The two figures come from different documents and different assumptions, and they are not directly comparable.

A battery stores electricity for later. Independent guidance describes combining solar panels with a home battery to store free, renewable electricity to power your heat pump, making the household less reliant on grid electricity¹⁰. A heat pump, by contrast, provides heating and hot water for the home, drawing heat from air, ground or water and using electricity to move it rather than burning a fuel¹¹.

Why solar panels usually come first

Solar comes first for three reasons: it produces something the other two consume, it is the least disruptive to install, and it starts earning from the day it is commissioned.

The generation point is the strongest. Independent guidance states that you can use solar panels to generate electricity that can help power a heat pump, and that this reduces how much electricity you buy in⁸. A heat pump without solar runs entirely on imported electricity. A heat pump with solar runs partly on self-generated electricity, and independent guidance notes that a solar battery can increase your savings even further by storing the sun's energy to power your heat pump later in the day¹.

There is also a tax treatment that favours doing solar and storage together. Official guidance sets out that where the installation is carried out at the same time, the customer perceives that it is receiving a single supply, and the battery is a better means of enjoying the principal supply of solar panels, the battery is included in the single supply of the solar installation for VAT purposes¹³. The same guidance records that it was necessary to include the cost of all materials relating to the solar panel and battery and which were left in place after the installation¹⁴. That is a condition to check with an installer, not an automatic outcome.

The practical precondition is the roof. Official guidance states plainly that your roof must be in good condition¹⁵. Building regulations will normally apply to installing solar panels on your roof¹⁶, and one of the reasons is the additional loading on the roof structure¹⁶. Building Regulations approval is likely to be needed to add a solar panel to the roof of a home¹⁷. In Northern Ireland, permitted development for roof-mounted solar PV or solar thermal equipment carries a condition that the primary purpose of the equipment would be to provide heat or energy for use within the curtilage of the dwellinghouse¹⁸.

Where a battery fits in the sequence

A battery sits between solar and a heat pump because it solves a timing problem. Solar generates in the middle of the day; heating demand peaks in the morning and evening. Independent guidance describes the battery's role as storing free, renewable electricity to power your heat pump later, making the household less reliant on grid electricity¹⁰.

The tariff is where the battery earns its place. Independent guidance recommends a dedicated solar and battery tariff, or a good export tariff matched with a dynamic import tariff or an Economy 7 tariff²¹. For a household running a heat pump, the same guidance suggests a heat pump tariff that includes a peak rate, using the battery to power the heat pump during expensive periods²¹. That is a statement about tariff design, not a recommendation of any particular product or supplier.

Storage is not only electrical. Independent reporting describes heat battery technology developed by a Scottish innovator which stores energy using a phase change material, used in properties such as flats with space constraints instead of hot water cylinders²². That matters for households without room for a cylinder or a large electrical battery.

The counterweight is cost. Independent research found that high upfront costs mean these systems do not always provide the strongest financial return at current technology costs⁴. A battery added before a heat pump is therefore a bet on future tariff shapes as much as a present saving.

When a heat pump makes sense as the first step

There are cases where the heat pump comes first, and they are usually about the heating system rather than the electricity supply.

If the existing heating is at the end of its life, replacing it with a heat pump avoids paying twice. Independent guidance notes that in all cases, replacing an existing fossil fuel heating system with a heat pump will save carbon emissions, with the amount depending on the size of your home and the type of heating system being replaced¹. Official guidance puts the carbon saving at up to 65% compared with a gas boiler⁵. Independent guidance describes heat pumps as much more energy efficient than boilers and electric heating¹¹, and official guidance states they are typically over three times more efficient than the most efficient gas boilers or electric heaters²³.

Fabric comes before either. Independent guidance states that topping up your home's wall, floor and loft insulation before installing a heat pump will help reduce its running costs¹. That is the same logic as a fabric first approach, and it applies whether the heat pump or the solar comes first.

Heat pumps also work with existing emitters more often than households expect. Independent guidance states that heat pumps can work with radiators or underfloor heating, but some types can work without either⁸. Where a heat pump is the first step, the household is buying lower-carbon heat immediately and adding self-generation later.

How the three work together: solar powering a heat pump

The combination is where the numbers get interesting, and where the evidence is strongest.

Independent research found that in some cases, energy bills were reduced by more than 80% compared with a gas-heated home on a standard tariff when a heat pump, solar panels and battery storage were operated on an appropriate tariff⁴. The same research found that the savings identified do not rely on households changing their heating patterns or actively altering their behaviour to respond to tariff signals⁴. Official guidance states that installing solar PV and battery storage, alongside a heat pump, can significantly lower bills in all cases²⁴.

The mechanism is straightforward. Solar generates electricity, the battery shifts it to the evening, and the heat pump converts it into heat at a ratio of more than one unit of heat per unit of electricity. Independent guidance describes heat pump technology as transferring energy from outside to heat your water, using electricity but delivering more heat energy than the electrical energy used²⁵. Official guidance describes heat pumps as using electricity to draw a larger amount of heat from either air, ground or water²⁶.

There is a distinct product category worth separating out. A solar assisted heat pump has a large, flat evaporator panel that absorbs heat from sunlight falling directly onto it and from the air around the panel²⁵. It heats water by absorbing heat from direct sunlight and from the air²⁵, and typical domestic installations only need one or two evaporator panels²⁵. These are generally used for heating water rather than the rooms in your home²⁵. The savings depend on how much hot water you use and what system you currently use to heat your hot water²⁵.

What a heat pump does and does not change about solar output

A heat pump does not change how much electricity a solar array produces. It changes how much of that electricity is used on site rather than exported, and it changes the household's total electricity demand.

The distinction matters because the two technologies are often described as if one boosts the other. Independent guidance states that heat pumps are much more energy efficient than boilers and electric heating¹¹, and that heat pumps provide your home with energy efficient, low carbon heating¹⁰. None of that alters the panel's output. What it alters is the value of each kilowatt hour generated, because a unit of electricity used to run a heat pump delivers more heat than the same unit used in a resistive heater.

Solar thermal is a different case again. Official guidance states that solar water heating works well with heat pumps because together they provide efficient water and space heating, at a more expensive cost¹². The cost caveat is part of the finding, not an aside.

On the planning side, Scotland's permitted development guidance confirms that no output limit is applied to air source heat pumps or solar panels²⁷. That is a Scottish position and should not be read across to the other nations.

Cost and payback: how the order affects your bills

There is no published price in the evidence for any of these three measures, and prices are installer-quoted. What the evidence does give is the structure of the bill and the direction of the savings.

Energy bills are built from wholesale costs, network costs, operating, debt and industry costs, EBIT, policy costs, VAT, the type of energy used, the type of meter installed and how you pay²⁸. That matters because solar and a battery act on the wholesale and network components by reducing imported units, while a heat pump changes the type of energy used and the meter's role in the household's costs.

The order affects payback in three ways. First, solar installed before a heat pump means the heat pump's running cost is lower from day one, because part of its electricity is self-generated. Second, a battery installed before a heat pump means the household can shift cheap or self-generated electricity into peak heating hours, which independent guidance links to a heat pump tariff with a peak rate²¹. Third, doing solar and a battery together can attract single-supply VAT treatment where the conditions are met¹³.

The honest limit is the one independent research states: high upfront costs mean these systems do not always provide the strongest financial return at current technology costs⁴. Official guidance confirms the direction of travel, that solar PV and battery storage alongside a heat pump can significantly lower bills in all cases²⁴, but the size of that reduction depends on the tariff, the fabric and the sizing.

For households weighing the sequence against other work, payback periods for home energy measures compared sets out how the measures sit against each other, and checking your electricity supply before adding a heat pump, charger or battery covers the connection question that applies to all three.