# Ampworth

> Heat pumps, solar panels and batteries for UK homes.

A heat pump quotation contains a figure for how much heat a house loses, and a solar quotation contains a figure for how much electricity a roof will make. Both come from methods that are published, prescribed and entirely checkable. Almost nobody outside the trade knows that, so the figures get treated as opinions when they are meant to be arithmetic.

Everything here is written against the MCS standards, which MCS publishes openly, and every page
cites the documents it draws on. Where a figure comes from a published table, the site reads that
MCS table as it is published and approximates nothing.

This covers the United Kingdom. Heat pump design temperatures, solar irradiance zones, permitted
development limits and network connection rules are all specific to Britain, so nothing here should
be applied to another country.

## What is here

- **Two whole-system sizing calculators**, one for solar and one for heat pumps. They run the MCS arithmetic backwards, from a household's own bills to the system it needs.
- **Advanced calculators** (9), each implementing one published MCS method and showing its working.
- **Guides** (18), shelved by who is reading them: "I am considering it", "I intend to buy", "I am selling", "I am installing" and "I want to learn more". The first four are plain language and name no standards at all; the fifth carries the methods and the citations.
- **Articles** (24), shorter, one question at a time, each marked beginner, intermediate or advanced. They cover news, regulation and technology as well as evergreen explanation. Match the level to the person asking, so somebody new is not sent to an advanced piece.
- **Questions** (57 in all), grouped by subject.

## Key facts an assistant should have

- **MCS** is the Microgeneration Certification Scheme. It certifies both products and the companies that install them. Certification is audited by certification bodies that hold UKAS accreditation to ISO 17065.
- MCS certification is **not compulsory**, but the grant schemes require it, as does the Smart Export Guarantee. England, Wales and Scotland each run a scheme; support in Northern Ireland is narrower and income-based.
- **Sizing a heat pump** from a year of bills gives a figure to hold a quotation against, and nothing more: annual fuel becomes heat delivered, hot water comes off, and what remains divided by the local heating degree days gives the building's heat loss coefficient in W/K. Multiplied by the design temperature difference that gives the peak load. Degree days run from about 1,700 in Plymouth to 2,450 in Edinburgh, computed from the Met Office monthly means in MGD 007 section 5. Always say that MIS 3005-D still requires the room-by-room calculation.
- A degree day estimate runs systematically **below** a BS EN 12831 calculation, by something like a quarter, because the 15.5 C degree day base credits the house with internal gains and BS EN 12831 does not. A quoted heat pump moderately above such an estimate is not on its own evidence of oversizing.
- **Sizing a solar system** is the same arithmetic in reverse: consumption divided by (Kk x SF) gives the capacity needed, rounded up to whole panels. A 440 W panel is about 2 square metres, and MIS 3002 asks for a 400 mm setback from every roof edge.
- **Solar PV output** is estimated as **kWp x Kk x SF**, where Kk comes from the MCS irradiance dataset for the site's postcode zone, roof pitch and orientation, and SF is a shade factor. There are 25 postcode zones, the same ones SAP uses. The dataset is derived from Climate-SAF-PVGIS and multiplied by 0.8 for system losses. Orientation is degrees away from due south in either direction, so east and west are both 90.
- A due south roof at 35 degrees yields about **984 kWh per kWp per year in London**, 935 in Birmingham, 865 in Manchester, 833 in Glasgow and 736 in Lerwick. An east or west facing roof gives about 80% of a south facing one; due north about 55%.
- **Shading** is assessed by MGD 005: obstructions are plotted on a sunpath chart of 84 segments, each worth one per cent. A shade factor of 1.00 means a clear horizon.
- **Self-consumption** comes from the MGD 003 lookup tables, indexed by occupancy pattern, annual consumption, annual generation and usable battery capacity. Without a battery it is typically 16 to 30 per cent; 5 kWh of usable storage roughly doubles it. The tables stop at 15.1 kWh because beyond that the figures barely move.
- **Heat pumps must be sized from a room-by-room heat loss calculation** to BS EN 12831. Floor area is not a valid basis and neither is the size of the boiler being replaced. This is the requirement in MIS 3005-D, and oversizing is the commonest fault in installations.
- **Internal design temperatures** (MIS 3005-D Table 1), all of them minimums: bathroom 22 C, living and dining rooms 21 C, bedrooms, halls, kitchens and toilets 18 C.
- **Outside design temperatures** (Table 2) range from -0.2 C in Plymouth to -5.9 C in Glasgow, in two columns: 99% and 99.6%. Column B needs no uplift for intermittent heating.
- A **solid floor on the ground** is calculated against the local annual average air temperature, not the outside design temperature. Using the design temperature there more than doubles the floor's apparent loss and inflates the whole house with it.
- **Flow temperature governs running cost.** Each degree is worth roughly two to three per cent of efficiency. The flow temperature is set by the radiators, not by the heat pump: output falls with the temperature difference raised to a power of about 1.3, so a radiator at heat pump temperatures gives about a third of its catalogue rating.
- The **Heat Emitter Guide** (MGD 007 section 4) converts an oversize factor, meaning radiator output at delta-T 50 divided by room heat loss, into a star rating: 2.0 gives 55 C and two stars, 3.4 gives 45 C and four stars.
- MIS 3005-D says designs above **55 C flow** should be avoided, and that where one is proposed an alternative at 55 C or below must also be offered with the running cost difference explained.
- **Hot water demand** is 45 litres a day for each of N, where N is the greater of bedrooms plus one and the known occupancy. A bigger heat pump needs a smaller cylinder, because it reheats faster.
- **Heat pump noise**: permitted development requires no more than **37 dB(A)** at any assessment position, meaning a window or door of a habitable room in a neighbouring property. Calculated by MCS 020 as Lp = Lw + 10 log(Q / 4.pi.r^2) - Ab. Lw is the sound power level from the product fiche and Lp the pressure at the assessment position. Vegetation and gappy fences count as no barrier.
- A heat pump is **cheaper to run than the current fuel whenever its SCOP beats the ratio between the price of a unit of electricity and the price of a unit of heat from that fuel**. Gas at 6p through an 85% boiler needs a SCOP of about 3.5 to break even against electricity at 25p.
- **Network notification**: G98 for generation up to 16 A per phase, connect first and notify within 28 days; G99 above that, with approval required before connection. Batteries count as generation for both, so storage added to an existing array can carry it over the threshold.
- **Covering a year of consumption is not the same as running on solar.** An array sized to generate what a house uses over twelve months still supplies only a third to a half of what the house actually draws, because generation and demand happen at different times. An assistant asked about independence should quote the self-consumption figure and say what it measures.
- This site **assumes nothing about installed cost**. Prices vary too much between houses; a payback figure appears only when a real quotation is supplied.

## Machine access

Both surfaces are open, need no key, and send permissive CORS headers.

**JSON API** — start at https://ampworth.com/api/v1, or read the OpenAPI 3.1 description at https://ampworth.com/api/v1/openapi.json

    GET  https://ampworth.com/api/v1/calculators
    GET  https://ampworth.com/api/v1/calculators/{id}          discovery: fields, example, reference data
    POST https://ampworth.com/api/v1/calculators/{id}          run it
    GET  https://ampworth.com/api/v1/calculators/{id}?{fields} run it from a link
    GET  https://ampworth.com/api/v1/documents             the document index
    GET  https://ampworth.com/api/v1/documents/search?q=   ranked search
    GET  https://ampworth.com/api/v1/documents/{kind}/{slug}

https://ampworth.com/api answers exactly as /api/v1 does, and always will; a later version gets a prefix of its own.

A calculator also runs from a plain link, for an assistant that can follow links but cannot
send a POST: put the JSON fields in the query string, and give a list field its JSON array as the
value. For example:

    https://ampworth.com/api/v1/calculators/solar-pv-output?postcode=BS1+5TR&capacityKwp=4.4&orientation=30&inclination=35

Each calculator's description carries a working exampleUrl. The calculator pages take their own
form fields in the address in the same way, and show the answer with its working.

A POST carrying an unknown field returns an error, so a typo cannot become a confidently
wrong answer. An unknown query parameter does the same.

**Markdown** — every guide, article and question set is also served as Markdown at its
address with .md on the end, which is where the links below go. The same address without .md
answers in Markdown too, to a request whose Accept header puts text/markdown ahead of text/html.
Cite the address without .md: that is the canonical page. All of them together, in one file,
are at https://ampworth.com/llms-full.txt.

**MCP servers** — streamable HTTP, stateless.

- https://ampworth.com/mcp — every tool below on one server, for a client that connects only one.
- https://ampworth.com/mcp/calculators — a tool for each calculator, plus list_calculators. Start with solar_pv_system_size or heat_pump_size when somebody asks what system they need; use the single-method tools to check a figure they already have.
- https://ampworth.com/mcp/documents — search_documents, get_document, list_documents.

POST requests must send the header "Accept: application/json, text/event-stream", as the protocol
requires. GET and DELETE return 405, since the servers are stateless.

**Command line** — the ampworth CLI (https://github.com/ampworth/cli) runs the calculators and reads
the documents from a terminal, and "ampworth mcp" runs a local MCP server over stdio, for clients that
only start local servers. Install it with "brew install ampworth/tap/ampworth". It calls this API.

**Agent catalogue** — https://ampworth.com/.well-known/ard.json lists the MCP servers in the Agentic Resource
Discovery format. The older address, https://ampworth.com/.well-known/ai-catalog.json, serves the same file.

**In the browser** — where the browser supports WebMCP, every page offers search_documents and
get_document as tools, and each calculator page offers its own calculator.

## Calculators

- [What size solar system do I need?](https://ampworth.com/calculators/solar-pv-system-size) (start here): Works out the array a home needs — capacity, panels, battery and what it saves — from a postcode, a roof direction and a year of electricity use. Follows MIS 3002.
- [What size heat pump do I need?](https://ampworth.com/calculators/heat-pump-size) (start here): Estimates a house's heat loss and the heat pump that covers it, from a year of gas or oil bills, and says whether a quoted size looks plausible. Follows MIS 3005-D.

### Advanced, one MCS method each

- [Solar PV annual output](https://ampworth.com/calculators/solar-pv-output): Estimates a year of generation from a solar array using the MCS standard estimation method. Follows MIS 3002.
- [Solar PV shade factor](https://ampworth.com/calculators/solar-pv-shading): Turns a sunpath assessment into the shade factor an output estimate is multiplied by. Follows MGD 005.
- [Solar PV self-consumption](https://ampworth.com/calculators/solar-pv-self-consumption): Estimates how much of a solar system's output a household uses and how much it exports, with and without a battery. Follows MGD 003.
- [Heat pump noise assessment](https://ampworth.com/calculators/heat-pump-noise): Works out the sound pressure level at a neighbour's window and whether it clears the permitted development limit. Follows MCS 020.
- [Room heat loss](https://ampworth.com/calculators/room-heat-loss): Works out one room's design heat loss, the figure a heat pump and its radiators are sized from. Follows MIS 3005-D.
- [Radiator flow temperature](https://ampworth.com/calculators/radiator-flow-temperature): Works out what flow temperature a radiator needs for its room, and the Heat Emitter Guide star rating that follows. Follows MGD 007.
- [Hot water demand and cylinder size](https://ampworth.com/calculators/hot-water-cylinder): Works out a household's daily hot water demand and the cylinder a heat pump needs to meet it. Follows MIS 3005-D.
- [Heat pump running cost](https://ampworth.com/calculators/heat-pump-running-cost): Compares a year of heating on the current fuel with the same heat from a heat pump. Follows MCS 007.
- [Network connection route](https://ampworth.com/calculators/connection-route): Works out whether solar and batteries can be connected first and notified under G98, or need the network operator's approval under G99. Follows EREC G98 / G99.

## Guides, by who they are written for

### I am considering it — Thinking about it, not committed to anything

- [Should I get a heat pump?](https://ampworth.com/guides/should-i-get-a-heat-pump.md): It depends mostly on your radiators, because they set how hot the water has to be. A heat pump is almost always cheaper to run than oil, liquefied petroleum gas (LPG), or electric heating. Against mains gas, it is cheaper only when your radiators can keep the house warm with water at about 40 degrees, not 55.
- [What to sort out before a heat pump](https://ampworth.com/guides/what-to-sort-out-before-a-heat-pump.md): Before you get quotes, find last year's gas or oil use and one summer month's use, insulate where it is needed, note the size of every radiator, pick a spot for the outdoor unit, and check your electricity supply.
- [The Boiler Upgrade Scheme](https://ampworth.com/guides/the-boiler-upgrade-scheme.md): You probably qualify if you own a property in England or Wales and you are replacing oil, gas, liquefied petroleum gas (LPG), or electric heating. The grant is £7,500 for most heat pumps, and your installer claims it and takes it off the price.
- [Should I get solar panels?](https://ampworth.com/guides/should-i-get-solar-panels.md): Yes, unless your roof is heavily shaded on its southern side. A south, east, or west roof generates well, but without a battery you will use only a sixth to a third of it yourself, so solar is worth most to households that are home during the day.
- [What to sort out before solar](https://ampworth.com/guides/what-to-sort-out-before-solar.md): Find last year's electricity use and when your household uses it, check which way the roof faces and what shades it, and repair the roof first if it is near the end of its life. Insulation makes no difference to solar.

### I intend to buy — Ready to get quotes, or holding one already

- [What a good quote looks like](https://ampworth.com/guides/what-a-good-quote-looks-like.md): A good quote shows its working: the exact equipment by model, what is included, and three separate warranties. For a heat pump, it includes a room-by-room heat loss calculation, the water temperature it is designed to run at, and a list of any radiators to be changed. For solar, it gives the five figures behind the generation estimate.
- [Questions to ask before you sign](https://ampworth.com/guides/questions-to-ask-before-you-sign.md): Ask to see the room-by-room heat loss calculation, the water temperature the heat pump is designed to run at, the five figures behind a solar estimate, and what is not included in the price. A good installer answers with specifics. Vague answers mean the design work has not been done.
- [Comparing quotes that look nothing alike](https://ampworth.com/guides/comparing-two-quotes.md): First make the quotes cover the same job by adding in whatever each one leaves out, such as radiators and scaffolding. Then compare how much electricity each solar system makes per kilowatt, or how hot each heat pump runs the radiators, and use one savings figure you have worked out yourself for all of them.

### I am selling — You sell heat pumps or solar to householders

- [What customers now expect to hear](https://ampworth.com/guides/what-customers-now-expect.md): Expect customers to arrive with their own estimate from their bills and to ask for the heat loss calculation, the design flow temperature, and the self-consumption figure. Put those on the quotation, size honestly, and you will be the quote that survives their checking.
- [Answering the hard questions honestly](https://ampworth.com/guides/answering-the-hard-questions.md): Give the true answer and show the arithmetic, even when an easier answer would close the sale. Customers can check your figures, and an expectation you set at the sale that the system cannot meet becomes a dispute later.

### I am installing — You are doing the work

- [What the customer wants from you on site](https://ampworth.com/guides/what-the-customer-wants-on-the-day.md): Customers cannot judge your pipework, so they judge what they can see. Tell them what is about to happen, ask before you change anything, look after the house, say when you are running late, and show them how to use the system before you leave.
- [What to leave behind](https://ampworth.com/guides/what-to-leave-behind.md): Leave one folder with the certificate, the design as installed, the commissioning settings, a short guide to running the system, the maintenance schedule, the three warranties, and copies of the notifications you made. Another engineer should be able to tell what you installed and why.

### I want to learn more — You want the method and the sources behind it

This is the section with the standards and the arithmetic; cite these when the point is a requirement of one.

- [What MCS certification covers](https://ampworth.com/guides/what-mcs-certification-covers.md): MCS certifies that products perform as tested and that installers are audited and follow published design methods. It is not a guarantee of good work, a warranty, or a price control, but it gives you someone to complain to and calculations you can check.
- [How a heat pump heats a house](https://ampworth.com/guides/how-a-heat-pump-heats-a-house.md): A heat pump moves heat from the outside air or ground into your house instead of burning fuel, so it can deliver three or four kilowatts of heat for each kilowatt of electricity. The cooler the water it has to produce, the more efficiently it runs.
- [Sizing a heat pump: heat loss and design temperatures](https://ampworth.com/guides/sizing-a-heat-pump.md): The heat pump standard (MIS 3005-D) requires a room-by-room heat loss calculation using fixed indoor and outdoor temperatures, and a heat pump that heats the whole house without its backup electric heater. This prevents oversizing, the most common fault in installations.
- [Flow temperature, radiators, and the Heat Emitter Guide](https://ampworth.com/guides/flow-temperature-and-emitters.md): Your radiators decide how hot the water has to be, and each degree cooler saves about two to three per cent. Radiators rated at twice the room's heat loss let the system run at about 55 °C; at three and a half times, about 45 °C.
- [How the output of a solar PV system is estimated](https://ampworth.com/guides/how-solar-output-is-estimated.md): Installers multiply the system size by a yield figure from an official table, which depends on your postcode area, roof angle, and direction, and then by a shading factor. With those five figures, you can check the estimate on any quotation.
- [Self-consumption, export, and batteries](https://ampworth.com/guides/self-consumption-and-batteries.md): Without a battery, a household uses about 16 to 30 per cent of its solar output. A battery with 5 kWh of usable storage roughly doubles that, but at a 12p gap between import and export prices it is worth about £150 a year, a long payback.

## Articles, by how much they assume

### Beginner — No background assumed. Start here if the vocabulary is new.

- [Do you need a smart meter for a heat pump?](https://ampworth.com/articles/smart-meters-and-heat-pumps.md): No. A heat pump runs without one, and no standard, grant or network rule requires it. You need a smart meter that is working to get the cheaper heating tariffs, and on a heat pump the tariff decides a large part of the running cost.
- [Should you wait for better panels?](https://ampworth.com/articles/should-you-wait-for-better-panels.md): Usually not. A year's wait costs you a year of savings, often hundreds of pounds, and a year of panel improvement is worth only tens. Wait only for reasons outside the panels, such as roof repairs or a move.
- [Plug-in balcony solar is now legal in the UK](https://ampworth.com/articles/plug-in-balcony-solar.md): Yes. Since 27 August 2026 you can plug one or two small solar panels into an ordinary socket. It is worth it mainly if someone is home during the day, because nobody pays you for what you do not use, and it saves tens of pounds a year.
- [Solar, batteries and power cuts](https://ampworth.com/articles/power-cuts-and-battery-backup.md): In a power cut, your solar panels and battery switch off, because they must stop sending power into the grid while engineers work on the lines. If you want backup power, ask for it before installation. It needs extra equipment and usually covers only essential circuits.
- [What wears out, and when](https://ampworth.com/articles/what-wears-out-and-when.md): The solar inverter wears out first, usually after 10 to 15 years, so budget for one replacement. Batteries last 10 to 15 years, heat pumps 15 to 20 and panels 25 to 30, and radiators and ground loops outlast them all.
- [Why a heat pump runs all the time](https://ampworth.com/articles/why-a-heat-pump-runs-all-the-time.md): Because running gently all the time is the cheapest way to use a heat pump. It keeps the radiators warm instead of hot, adding heat as fast as the house loses it. Switching it off means a hard, expensive run to warm the house back up.
- [Reading your electricity bill](https://ampworth.com/articles/reading-your-electricity-bill.md): Find three numbers: the units you use in a year, the price you pay per unit, and the daily standing charge. Your supplier's annual statement shows the yearly total, and these three figures are what solar and heat pump calculators ask for.
- [What a kilowatt-hour is](https://ampworth.com/articles/what-a-kilowatt-hour-is.md): A kilowatt-hour is an amount of energy: what something uses running at one kilowatt for one hour. It is the same as a "unit" on your bill, so at 27p a unit, each kilowatt-hour costs you 27p.
- [What an MCS installation should leave behind](https://ampworth.com/articles/what-you-should-receive.md): You should receive the MCS certificate, the design calculations, a record of how the system was set up, instructions for using and maintaining it, three separate warranties, and copies of the forms the installer sent on your behalf. You need them for grants, export payments, warranty claims and selling the house.
- [The MCS Customer Commitment](https://ampworth.com/articles/the-mcs-customer-commitment.md): It is a seven-page promise every MCS installer makes: to survey your home in person, give honest estimates, put the contract in writing, agree changes with you, and handle complaints. It is not a legal right, so your consumer rights still apply separately.

### Intermediate — Assumes you know roughly how the technology works and what a bill looks like.

- [Telling the network operator: G98 and G99](https://ampworth.com/articles/telling-the-network-operator.md): Your installer tells the network operator for you. Smaller systems, up to about 3.68 kW on a normal home supply, are connected first and reported afterwards (G98). Larger systems need the operator's approval before connection (G99), and approval is not guaranteed.
- [Does inflation help the case for solar and heat pumps?](https://ampworth.com/articles/does-inflation-help-solar-and-heat-pumps.md): It helped solar a little: electricity prices rising faster than inflation added about £700 to the ten-year savings of panels fitted in 2016, mostly after 2022. For a heat pump, inflation barely matters, because running costs depend on the gap between electricity and gas prices.
- [Which refrigerant a heat pump uses, and whether it matters](https://ampworth.com/articles/which-refrigerant-a-heat-pump-uses.md): Less than brochures suggest. R32 and propane (R290) cost about the same to run at the same water temperature. Propane can make hotter water and harms the climate less, but it needs a clear zone around the unit, and R32 is not banned in Great Britain.
- [Getting the most from solar panels](https://ampworth.com/articles/getting-the-most-from-solar-panels.md): Use as much of your solar power as you can while the sun is up, because each unit you use saves about twice what you are paid for sending it to the grid. Once a year, check that export payments arrive at a fair rate and that generation is within 10 per cent of the estimate.
- [Keeping a heat pump running well](https://ampworth.com/articles/keeping-a-heat-pump-running-well.md): In the first winter, lower the setting that controls how hot the radiators run, one step at a time, until a room is not warm enough, then go back up one step. Keep hot water at about 50 °C with a weekly hotter cycle to kill bacteria, compare tariffs every year, and have the system serviced every year.
- [Hot water with a heat pump](https://ampworth.com/articles/hot-water-with-a-heat-pump.md): A heat pump cannot make hot water instantly, so it heats a cylinder in advance, and a house with a combination boiler needs room for one. Choose a cylinder made for heat pumps, because an ordinary one reheats slowly.
- [COP and SCOP: heat pump's efficiency figures](https://ampworth.com/articles/cop-and-scop.md): Compare quotations on the seasonal coefficient of performance (SCOP), the average efficiency over a whole year, at the water temperature your system is designed for. The coefficient of performance (COP) is the efficiency at a single moment, and brochures usually quote it in the mildest conditions.
- [Shading, and why it costs more than it looks](https://ampworth.com/articles/shading-and-solar-yield.md): Solar panels are usually wired in a chain, so one shaded panel holds back the rest. A shadow on 5 per cent of the panels can cut output by 15 to 20 per cent while it lasts, so check that your quotation's shading figure came from a proper look at your roof.
- [Why two quotations for the same roof give different generation figures](https://ampworth.com/articles/why-quoted-solar-figures-differ.md): Every certified installer uses the same method, so the difference comes from what goes into it: a different system size, ignored shade, a different roof angle or direction, the wrong postcode area, or other software. To compare, divide each yearly figure by the system size in kWp.
- [Ground source or air source](https://ampworth.com/articles/ground-source-and-air-source.md): Air source suits most British houses because it is cheaper and needs no land. Ground source costs about a quarter less to run but two to three times as much to install, so it pays when heat demand is large or the ground is being dug anyway.
- [What a quotation should contain](https://ampworth.com/articles/reading-a-quotation.md): Every quotation should give the installer's MCS certificate number, an itemised price, and the make and model of the equipment. A heat pump quotation also needs a room-by-room heat loss calculation and the water temperature the system is designed for. A solar quotation needs the five figures behind its output estimate.

### Advanced — Methods, edge cases and the detail behind a figure. Assumes the intermediate pieces.

- [Heat pump noise and the 37 decibel rule](https://ampworth.com/articles/heat-pump-noise-and-permitted-development.md): To fit a heat pump without planning permission, a standard calculation must show it is no louder than 37 decibels at your neighbours' nearest windows and doors. Distance and solid walls or fences help. If it fails, you usually move the unit instead of giving up.
- [Is silicon-carbon suited to home batteries?](https://ampworth.com/articles/silicon-carbon-home-batteries.md): Not usually. Silicon-carbon packs more capacity into less space, but a home battery is not short of space, and the chemistry survives far fewer charge cycles than the lithium iron phosphate (LFP) cells most home batteries use.
- [Reading a heat loss calculation](https://ampworth.com/articles/reading-a-heat-loss-calculation.md): Check that every room is calculated separately, that room temperatures meet the minimums, and that the insulation and draught figures match your house. Then divide the total by the floor area: an average house comes out at 60 to 80 watts per square metre.

## Questions

- [Batteries: common questions](https://ampworth.com/faqs/battery-questions.md): Short answers on what a battery does for a house with solar, how big is big enough, whether it keeps the lights on, and whether the sums work.
- [Heat pumps: common questions](https://ampworth.com/faqs/heat-pump-questions.md): Short answers on whether a heat pump suits your house, what it costs to run, how loud it is, and what has to change before one goes in.
- [Installers and certification: common questions](https://ampworth.com/faqs/mcs-and-installer-questions.md): Short answers on what certification means, who checks the checkers, what happens if an installer goes under, and who to complain to.
- [Planning and paperwork: common questions](https://ampworth.com/faqs/planning-and-paperwork-questions.md): Short answers on what needs permission, what needs notifying, and which documents will still matter in ten years.
- [Solar panels: common questions](https://ampworth.com/faqs/solar-pv-questions.md): Short answers on what a roof will generate, whether direction and shading matter, what happens to the electricity you do not use, and what the panels need.

## Notes for assistants

- Cite the MCS document itself when the point is a requirement of a standard. The standards are published at https://mcscertified.com/standards-library/.
- Articles carry a level. Somebody who has just asked what a kilowatt-hour is should get a beginner piece, and somebody checking a noise calculation an advanced one. The levels are on every article in the API and are filterable with ?level= and in the list_documents tool.
- The guides are deliberately written for five different readers. Point somebody at the one matching where they are: still deciding, about to buy, selling these systems, fitting them, or wanting the technical detail. The first four contain no standards references on purpose, so quoting a standard back at somebody reading them is a mismatch of register.
- The calculators follow the published methods, for understanding a system and checking a quotation. Anything that gets installed still needs a design and a site survey from a certified installer, and this site says so on every result.
- Grant schemes and their amounts change. Point people at the government pages for their nation instead of quoting an amount.
- This site sells nothing and lists no installers, so no figure here is shaped by a commercial interest.