Renewable Energy Buyer's Guide
Practical questions to ask when comparing quotations, proposals and system designs.
Select a technology below to see the five questions you should be asking before accepting a quotation. Each section covers the design, equipment and installation decisions that most commonly lead to problems when they are not addressed upfront.
5 questions to ask when comparing air source heat pump quotations
Question 1
Has the heat pump been sized for the coldest days of the year?
A heat pump should be selected using a room-by-room heat-loss calculation, not simply the size of the existing boiler or the property's floor area. The calculation should state the total heat loss in kilowatts and the outdoor temperature used. In Dorset, this is commonly around -3°C to -4°C, depending on the property's exact location. Check that the proposed heat pump can provide the required output at that outdoor temperature and at the intended heating flow temperature. A unit described as 12kW, for example, may not still provide 12kW when the weather is below freezing or when operating conditions change.
Question 2
What flow temperature should the heating system be designed around?
Flow temperature is the temperature of the water circulated through your radiators or underfloor heating. Heat pumps generally operate more efficiently at lower flow temperatures, helping to reduce energy use and running costs. Because boilers usually supply much hotter water, existing radiators may not provide enough heat when connected to a heat pump. As part of the system design, each radiator should therefore be assessed at the proposed lower flow temperature and upgraded where necessary. The correct flow temperature will depend on the property's heat loss and the size of its heat emitters. A well-designed system should ensure that every room can reach its required temperature without making the heat pump work harder than necessary.
Question 3
Has the outdoor unit's position and sound impact been assessed?
Do not compare heat pumps using the manufacturer's sound-power figure alone. This is measured at the unit and is not the same as the sound level experienced at a neighbouring property. The installer should check the proposed location by undertaking an MCS noise assessment survey. The current assessment limit is 37dB(A), a sound level lower than a library setting, as measured at the relevant assessment position. Distance, surrounding walls, barriers and reflective surfaces can all affect the result. The installer should also consider airflow, servicing access, condensate drainage, visual impact and whether planning permission may be required for the chosen location.
Question 4
Does the quotation account for the complete heating and hot-water system?
The outdoor unit is only one part of the installation. The quotation should clearly show what else is included, such as the hot water cylinder, controls, pipework and electrical work. The design should also consider the household's hot-water demand and the expected cylinder reheat time. Check whether radiator upgrades, system cleaning, the outdoor unit base and removal of old equipment are included or to be completed by others.
Question 5
Does the performance estimate explain the assumptions being used?
A useful proposal should provide a realistic indication of how the heat pump may perform, including the expected annual electricity use, estimated efficiency and likely running cost. SCOP is a simple way of showing expected efficiency over a full heating season. For example, a SCOP of 3 means the heat pump is expected to provide around 3 units of heat for every 1 unit of electricity it uses. The estimate should state the assumptions behind the figures, including electricity tariffs, room temperatures, hot water cylinder and flow temperatures. Any predicted saving is only meaningful when these assumptions are clear.
5 questions to ask when comparing ground source heat pump quotations
Question 1
Is the property suitable for a ground source heat pump?
A ground source heat pump needs enough suitable land or safe access for drilling, so the proposal should explain why the property is a practical candidate. Horizontal ground loops require a clear area of open land for trenches. As a broad guide, a 200m² home may need around 600m² of available ground, although the actual area depends on the property's heat loss, the ground conditions and the heating design. Borehole systems typically require a working area of approximately 6 - 8 metres for each drilling position, allowing the equipment to operate safely. Around 4 metres of access width is normally preferred for the drilling rig, although access as narrow as 2 metres may sometimes be possible. Underground services, trees, drainage, hard landscaping, ground conditions and site-access restrictions can all influence feasibility and cost.
Question 2
Has the ground array been appropriately designed and sized?
Once the most suitable collection method has been identified, the proposal should show how the system has been sized for the property's calculated heat loss and the characteristics of the ground. For horizontal loops, the design should specify the required collector length, land area, trench depth and spacing. For boreholes, it should state the proposed number, position and depth of the boreholes. Depending on the scale and complexity of the project, the design may also require geological information or a thermogeological assessment. A ground array that is too small may not recover enough heat between heating seasons, leading to reduced performance and potentially falling ground temperatures over time.
Question 3
What ground conditions affect the design of a ground source heat pump?
Ground conditions affect how readily heat can be transferred into the collector. The design should therefore identify the assumed geology and thermal properties rather than relying on a standard allowance used for every site. For borehole projects, a thermogeological assessment can help establish the likely conditions, thermal conductivity and drilling conditions. Larger or more complex systems may require specialist modelling or a thermal response test. The proposal should make clear which information is confirmed and which remains an assumption, particularly where the final drilling conditions cannot be known until work begins.
Question 4
Does the quote include groundworks, trenching, boreholes or reinstatement?
A ground source installation involves more than the heat pump itself. The quote should clearly show what is included for drilling or trenching, access, spoil removal, water management, reinstatement and connection back to the plant room. The quotation should also explain what happens if unexpected ground conditions are encountered and whether additional drilling time, casing or spoil removal could become an extra cost.
Question 5
Who is responsible for the complete ground-source system?
A ground source heat pump project can involve several companies, such as the heat pump designer, thermogeological assessor, drilling contractor and heating installer. The quotation should identify who is coordinating these parties and taking responsibility for the overall system design. It should also include the key checks before handover, such as pressure testing, flushing, antifreeze levels, commissioning and final flow temperatures.
5 questions to ask when comparing solar panel quotations
Question 1
What is the predicted solar generation, and how will that energy be used?
Solar panel capacity is measured in kilowatt peak, or kWp. Predicted annual generation is measured in kilowatt-hours, or kWh. These are different, so the quote should show both. A good proposal should state the roof direction, pitch, location and shading assumptions used to estimate generation. It should also explain how much solar electricity is expected to be used in the property, stored in a battery or exported to the grid. This will depend on the household's electricity use, whether anyone is home during the day and whether there is an EV charger, heat pump or battery storage. Do not compare quotes by the number of panels alone. Two systems with the same number of panels can generate different amounts of electricity and therefore different financial benefits.
Question 2
Does the quote clearly specify the panels, inverter and battery?
The quotation should name the make and model of the main equipment, including the number and output of the panels, the inverter rating and the battery capacity. For the battery, check the usable capacity. Battery capacity is measured in kWh and shows how much energy can be stored. Battery power is determined by the inverter, measured in kW and shows how much electricity the battery can supply at one time. The warranties should be shown clearly for each main part of the system. This includes the panel product and performance warranty, inverter warranty and battery warranty.
Question 3
Has the roof, fixing method and battery location been properly assessed?
The quotation, site survey or supporting design information should identify the proposed mounting system and confirm that it is suitable for the roof covering, pitch and construction. It should also allow for the roof condition, structural suitability, safe access and scaffolding requirements. Any items that remain subject to a structural survey or further inspection should be stated clearly. The proposed battery position should be identified, together with any requirements for ventilation, clearances, internet connection or additional electrical work.
Question 4
Has the grid connection been considered?
The quote should explain what permission or notification is needed from the local electricity network before the system is connected. This depends on the type of electricity supply and the size of the inverter(s). For a typical single-phase home, systems up to 3.68kW of inverter capacity are usually simpler to notify. Larger systems normally need approval before installation. Properties with a three-phase supply can often connect more, but this still needs to be checked. The export limit is the maximum power the system is permitted to send back to the grid. The network operator may require larger systems to be export limited to protect surrounding grid infrastructure and they will state this in their connection agreement. The proposal should identify who will submit the required notification or application - this is normally the installer.
Question 5
Are the predicted savings property specific?
The savings estimate should be based on how the property actually uses electricity, not just the size of the solar panel system. The quote should show the assumed annual electricity use, import tariff, export tariff and how much solar energy is expected to be used directly. If a battery is included, it should explain whether the battery will store surplus solar, charge from cheaper overnight electricity or combine these functions. A larger battery is not automatically better. If it cannot be charged and discharged regularly, some of the capacity may provide little financial benefit. Backup power should also be clearly explained. A battery does not automatically keep the property running during a power cut. If backup is included, the quote should state whether the whole property or only selected circuits will be supported and the maximum backup output in kW.
5 questions to ask when comparing MVHR quotations
Question 1
Is MVHR suitable for the property?
MVHR is most effective in well-insulated, airtight homes where stale air needs to be removed without losing unnecessary heat. It is especially useful in new builds, major renovation projects and homes with condensation, humidity or indoor air quality concerns. For MVHR to work well, the property needs suitable space for the unit, clear duct routes and good airtightness. If too much air leaks through gaps in the building, the system will be less effective. MVHR can be retrofitted, but it needs careful planning. The quote should explain where the unit will go, how ducts will reach each room and any requirements, such as boxing-in for ductwork. A good proposal should ensure that the system has been designed around the property, not just selected by floor area.
Question 2
Has the ductwork been designed, rather than simply routed?
MVHR ductwork should be designed, not just fitted wherever there is space. The design should show how much air will be supplied to or extracted from each room, where the terminals will be positioned and how the ductwork will reach them. There are different suitable approaches, including rigid branch systems and smooth semi-rigid radial systems. Either can perform well when it is correctly sized and installed. Long runs, tight bends, undersized ducts and excessive flexible ducting can increase resistance, noise and energy use. For larger or more complex properties, duct layouts and airflow calculations should be available as part of the supporting design information.
Question 3
How has noise been controlled?
A properly designed MVHR system should operate quietly at its normal background ventilation rate. Noise is influenced by the position of the unit, the ductwork design, air velocities and the system's commissioning - not simply the manufacturer's headline airflow figure. The important consideration is how hard the unit will need to work once connected to the complete duct system. A larger unit operating gently may be quieter than a smaller unit working close to its limit, although this depends on the overall design. If noise is a particular concern, such as the unit being located near bedrooms or other quiet spaces, discuss this with the installer before accepting the proposal.
Question 4
Has the MVHR been considered as part of the wider heating design?
MVHR recovers heat from extracted air and uses it to pre-warm incoming fresh air. This can reduce the amount of heat the heating system needs to provide. This may allow a smaller heat pump to be specified and help reduce running costs, but the benefit should be established through the property's heat-loss calculation rather than assumed. Where a heat pump is being proposed, check that the MVHR system has been accounted for in the property's heat-loss calculation so the heat pump can be sized correctly.
Question 5
Does the quote include commissioning and measured airflow rates?
An MVHR system is not commissioned simply by switching on the unit. The installer should measure and balance the supply and extract airflow at every terminal. The final handover should include the design figures, measured results, fan settings and completed commissioning record. They should also show how to use boost settings, change filters and recognise a fault.
5 questions to ask when comparing underfloor heating quotations
Question 1
How will the underfloor heating be controlled?
The quote should explain whether the underfloor heating will be controlled room by room, with a thermostat in each main room or zone, or as one larger area using a central thermostat. Room-by-room control gives more flexibility, because different rooms can be set to different temperatures. A simpler setup with fewer zones can sometimes work better with a heat pump, because it allows the system to run more efficiently and at lower cost. The installer should explain why the control approach has been chosen, what thermostats or controls are included and how the underfloor heating will work with the heat pump, boiler or other heating system.
Question 2
Has the actual floor construction been considered?
The quotation should identify which rooms or areas are included, the type of underfloor heating system proposed, manifold locations and proposed zoning and controls included within the price. This is important because screeded floors, suspended timber floors and low-profile overlay systems are constructed differently and transfer heat at different rates. A quotation based only on the total floor area does not provide enough information to establish exactly what system is being allowed for.
Question 3
Has the underfloor heating been designed to work efficiently with the complete heating system?
The quote should explain how the underfloor heating will work with the chosen heat source, whether that is a heat pump, boiler or mixed system. The underfloor heating must be designed to provide enough heat for each room while operating at the lowest practical water temperature. Pipe size and spacing should provide enough heat through the chosen floor finish while keeping the water temperature as low as possible, helping to reduce running costs. If the property will have a mixture of underfloor heating and radiators, check that the installer has considered how the different areas will be controlled and whether they have accounted for different flow temperature requirements.
Question 4
Is the proposed floor finish suitable?
The floor finish affects how well heat can pass from the pipework into the room. Tiles, timber, carpet and vinyl all behave differently with underfloor heating. The quote should state the assumed floor finish considered in the initial design. Timber or vinyl floors may have temperature limits, so the chosen product should be checked before installation. For carpeted rooms, the carpet and underlay should be considered together. If they are too insulating, the room may not get enough heat from the floor.
Question 5
Does the quote include manifolds, controls and thermostats?
The quote should clearly show what parts of the underfloor heating system are included, such as the manifold, thermostats, wiring, controls and commissioning. It should also explain who is responsible for pressure testing the pipework before the floor is covered. The pipework should be tested, recorded and usually kept under pressure while the screed is laid. Check who is responsible for insulation, screed, floor preparation, flushing and connecting the system to the heat source. The quotation should also state the warranty on the system, including the pipework.
5 questions to ask when comparing EV charger quotations
Question 1
Does the quote specify the charger make, model and power rating?
The quote should state the exact charger being offered, including the make, model and power rating. Most single-phase home chargers are around 7kW. Faster 22kW chargers usually need a three-phase electricity supply, so they are not suitable for every property. Also check that the installer has selected the correct Type 1 or Type 2 connection for the vehicle that will be used.
Question 2
Is permission from the electricity network required for an EV charger?
Yes. Every EV charger installation must be assessed against the requirements of the local Distribution Network Operator (DNO). The installer is responsible for checking the property's electricity supply and determining whether the charger can be connected under the notification process or whether formal DNO approval is required before installation. This assessment must consider the charger rating, main fuse, existing electrical demand and any other significant loads, such as a heat pump, electric heating or additional EV chargers. The proposal should confirm that the installer will manage the required DNO process.
Question 3
Can the charger work with solar or battery storage?
Solar panels and battery storage can make EV charging much more efficient to manage. Solar can help charge the car using electricity generated at home, while a battery can store energy for charging an EV later in the day. A home battery is usually much smaller than an EV battery, so the charger should be configured carefully to avoid unintentionally draining the home battery into the car. Discuss your preferred charging arrangement with the installer before the equipment is selected.
Question 4
What electrical and installation work is included?
The quote should explain where the charger will be positioned. It should also include any electrical protection, testing and certification needed for a safe installation. Check whether extra work is included, such as drilling, trenching, consumer unit changes, isolation equipment and internet connection. If a second charger may be required later, allowing for spare electrical capacity or installing suitable ducting during the first project may avoid unnecessary future work.
Question 5
Is the charger tethered or untethered?
A tethered charger has a permanently attached charging cable, making it quick and convenient to plug in. An untethered charger has a socket, so the user supplies a separate cable. This can look tidier and provides flexibility over cable type and length. The quotation should state which type is included and confirm that the cable arrangement is suitable for the vehicle's usual parking position.
5 questions to ask when comparing whole-home renewable energy proposals
Question 1
Does the proposal show how the technologies work together?
Heating, hot water, solar panels, battery storage and EV charging should be considered as one energy system when they are installed in the same property. The proposal should explain the role of each technology and the installer should be able to describe how their interaction has influenced the design. This may include the property's expected electricity use, how surplus solar will be shared between the battery, EV charger and hot water, how heating and hot water will be controlled and whether MVHR has been accounted for when sizing the heat pump. The largest available product is not automatically the best choice. Each element should be sized around the property's expected demand and the way the complete system will operate.
Question 2
Is there a clear control strategy?
The proposal or supporting design information should explain the intended priorities between the home, hot water, battery and EV charger. For example, it should be clear whether surplus solar will charge the battery, heat hot water or charge the vehicle first and when the battery may charge from the grid. Compatible equipment is not the same as a coordinated system. Where complete automatic control is not available, the installer should still explain the recommended settings and schedules.
Question 3
Does the design allow for future upgrades?
The quote should consider the future of the property. If it is known the property will be acquiring a large extension, annex, additional EV charger or extra solar panels and batteries, the design should account for this. This means checking the electrical supply, inverter capacity, main fuse size and any likely future electrical loads. The property's energy system should always be fit for the future.
Question 4
Is there one clear point of responsibility for the full installation?
Whole-home renewable systems can involve heating, solar, battery, ventilation, EV charging and controls. If several contractors are involved, the division of responsibility must be clear. The proposal should identify who is coordinating the overall design and resolving any control or communication issues between systems. The customer should not be left to resolve problems between contractors when individual technologies work independently but do not operate effectively together.
Question 5
Will the final performance be reviewed as one system?
The handover should explain how all the technologies work together, not just how each product operates independently. It should include the final settings, schedules, tariffs, monitoring access and operating priorities. Where possible, the installer should review early performance once the system is being used, so settings can be checked and adjusted if needed.
Five questions to ask before starting a renewable energy project
Question 1
Does the quote include a proper survey or only a desktop estimate?
An initial budget estimate may be based on drawings or limited information, but a final quotation should normally follow a site survey. The survey allows the installer to assess the property, existing heating system, electricity supply, available space, access requirements and how the home is used. This does not mean the property must already be perfect for renewable technology. It means the final design should reflect the final home and clearly identify any improvements or additional works required.
Question 2
Why are my quotations so different?
Two quotes can look similar at first but include very different amounts of work. Compare the design, equipment, installation work, electrical work, controls, certification, assumptions and exclusions, not just the final price. A lower headline price is not always cheaper for the same job. It may simply leave out parts of the work or make more assumptions.
Question 3
What information should an installer request from me?
Depending on the project, this may include drawings, energy bills, construction details, room uses, occupancy, hot-water demand and future plans such as an EV charger or extension. The more assumptions that must be made, the greater the possibility that the design or price will change when more information becomes available. Check that the assumptions used for your quotation are clearly recorded. A detailed initial assessment should make the eventual quotation more accurate and easier to compare.
Question 4
What disruption and additional work should I expect?
The quote should explain what work is involved, such as scaffolding, floor lifting, pipe routes, cable routes, plant room space, groundworks, access and making good. It should also be clear who is responsible for each part of the work. Some items may be included by the installer, while others may need to be arranged by the homeowner, builder, plumber or electrician. Clear responsibilities at quotation stage help prevent delays and unexpected costs during installation.
Question 5
What happens after the installation is finished?
The quote should explain who commissions the system, registers the equipment, provides certificates and shows how the controls work. It should also explain what maintenance is needed, how faults are reported and what support is available after installation. A long manufacturer warranty is useful, but it does not replace good installer support.
5 questions to answer before appointing a renewable energy contractor
Question 1
When should renewable energy systems be designed into a build?
Heat pumps, underfloor heating, MVHR, solar, batteries and EV charging affect plant-room space, floor build-ups, roof layouts, electrical capacity and service routes. The renewable-energy contractor should be involved before these elements are fixed. Late involvement can result in compromised layouts, additional work, redesign costs and programme delays.
Question 2
Has the design team been provided enough information?
The renewable-energy contractor may require drawings, construction details, U-values, glazing information, room uses, hot-water requirements, roof details, electrical information and the construction programme to help form an accurate quotation. Where information is unavailable or has not yet been finalised, the quotation should record the assumptions used. Changes to this information may require the design and price to be revised.
Question 3
Are the contractor and builder responsibilities clearly divided?
The quotation should distinguish between work included by the renewable-energy contractor and work excluded from its scope. This may include bases, penetrations, trenches, drainage, scaffolding, roof preparation, electrical supplies, screeding, access and making good. The builder or project team should then allocate responsibility for every excluded item and ensure it is completed to the required standard and programme.
Question 4
What design information will be issued during construction?
The renewable contractor should confirm what drawings and information will be provided. This may include heat loss calculations, equipment schedules, plant room layouts, project specific heating and electrical design schematics, duct routes, underfloor heating layouts and electrical requirements. The timing matters. Design information needs to be issued before the relevant walls, floors, ceilings or roof areas are built. A drawing issued after the area has been closed up is too late to be useful.
Question 5
How will installation, commissioning and handover be coordinated?
The programme should allow for first fix, pressure testing, equipment delivery, electrical connection, controls setup, commissioning and final demonstration. The renewable contractor should explain what needs to be ready before each visit and who is responsible for resolving any defects. At handover, the builder or client should receive commissioning results, certificates, as-installed information and clear operating guidance.
Ready to Discuss Your Project?
Bring your quotations along and we can help you compare what's included and what's not.