Put our calculators on your own site

Three of our tools are free to embed on any website: the retrofit plan, heat pump costs and EPC ratings. One line of HTML each, no account, no cookies and no tracking scripts loaded on your readers. All we ask is that you keep the credit link.

Retrofit plan

Four questions about a home give an ordered list of upgrades: insulation first, cheapest payback first, then a heat pump sized for the home after it, each with its cost, the saving homes like it measurably made, and the payback. It runs the same script as our full retrofit plan, so the two cannot disagree, and nothing the reader enters leaves their browser. Suited to lenders, landlords' portals and any page about improving a home.

<iframe
  src="https://www.retrofitplanner.co.uk/embed/retrofit-plan/"
  title="Retrofit plan"
  loading="lazy"
  style="width:100%;max-width:640px;height:760px;
         border:1px solid #e5e3dc;border-radius:12px">
</iframe>
<p style="font-size:13px">Plan by
  <a href="https://www.retrofitplanner.co.uk/retrofit-plan/">
    Retrofit Planner</a>
</p>

<script>
addEventListener("message", function (e) {
  if (e.origin !== "https://www.retrofitplanner.co.uk") return;
  if (!e.data || !e.data.rpHeight) return;
  var f = document.querySelectorAll(
    'iframe[src*="retrofitplanner.co.uk/embed/"]');
  for (var i = 0; i < f.length; i++) {
    if (f[i].contentWindow === e.source) {
      f[i].style.height = e.data.rpHeight + "px";
    }
  }
});
</script>

Heat pump cost calculator

Installed cost, the Boiler Upgrade Scheme grant (£7,500, or £9,000 for oil or LPG homes off the gas grid), running costs against the reader's current heating, and payback. It runs the same cost model as our full heat pump calculator, and we test every money figure against it, so a reader who follows the link sees the same numbers. It also shows what a dedicated heat pump tariff would cost, which is where most of the saving comes from.

<iframe
  src="https://www.retrofitplanner.co.uk/embed/heat-pump-calculator/"
  title="Heat pump cost calculator"
  loading="lazy"
  style="width:100%;max-width:640px;height:560px;
         border:1px solid #e5e3dc;border-radius:12px">
</iframe>
<p style="font-size:13px">Calculator by
  <a href="https://www.retrofitplanner.co.uk/heat-pump-calculator/">
    Retrofit Planner</a>
</p>

<script>
addEventListener("message", function (e) {
  if (e.origin !== "https://www.retrofitplanner.co.uk") return;
  if (!e.data || !e.data.rpHeight) return;
  var f = document.querySelectorAll(
    'iframe[src*="retrofitplanner.co.uk/embed/"]');
  for (var i = 0; i < f.length; i++) {
    if (f[i].contentWindow === e.source) {
      f[i].style.height = e.data.rpHeight + "px";
    }
  }
});
</script>

EPC rating calculator

Estimates the band from the age, walls, loft, glazing and heating, then ranks the cheapest measures that reach the reader's target band, with points and costs after grants. It runs the same point model as our full EPC calculator, tested against it on band, points and total cost. Useful on any page about selling, letting or improving a home, and on landlord pages before the 2030 band C standard.

<iframe
  src="https://www.retrofitplanner.co.uk/embed/epc-calculator/"
  title="EPC rating calculator"
  loading="lazy"
  style="width:100%;max-width:640px;height:640px;
         border:1px solid #e5e3dc;border-radius:12px">
</iframe>
<p style="font-size:13px">Calculator by
  <a href="https://www.retrofitplanner.co.uk/epc-calculator/">
    Retrofit Planner</a>
</p>

<script>
addEventListener("message", function (e) {
  if (e.origin !== "https://www.retrofitplanner.co.uk") return;
  if (!e.data || !e.data.rpHeight) return;
  var f = document.querySelectorAll(
    'iframe[src*="retrofitplanner.co.uk/embed/"]');
  for (var i = 0; i < f.length; i++) {
    if (f[i].contentWindow === e.source) {
      f[i].style.height = e.data.rpHeight + "px";
    }
  }
});
</script>

The resize script handles every widget, so if you embed more than one on a page you only need it once.

If your CMS strips scripts

Some editors remove script tags. Drop the script block and set a taller fixed height instead: 1500px for the retrofit plan, 900px for the heat pump calculator and 1100px for the EPC calculator. The widget then scrolls inside the frame rather than resizing.

The terms, in plain English

It is free. Commercial sites included. No account, no key, no usage limit.
Keep the credit link. The line under the iframe, pointing to the calculator, is the whole price. Leave it as a normal link that search engines can follow.
Nothing tracks your readers. The widgets set no cookies, load no analytics and make no third-party requests. They need no mention in your cookie banner.
Do not present them as your own. You can wrap a widget in your own page and write your own introduction, but do not remove the attribution or claim the model.
We keep them current. When the price cap or the grant changes we update them, and your copy updates with it. If we ever retire a widget we will leave a redirect rather than break your page.

Who this suits

Installers and heating engineers use the heat pump calculator on a service page so a visitor can size the job before calling. Estate and letting agents use the EPC calculator next to listings, where the band is already on the page. Energy and money blogs use either to answer the cost question inside an article instead of sending readers away. Councils and community energy groups use them on advice pages. If you want a widget we do not offer yet, tell us on the contact page.

Technical notes

Detail	Value
Page weight	Before compression: 18 KB for the EPC calculator in one file, 25 KB for the heat pump calculator in two, 33 KB for the retrofit plan in three. All from our own domain.
Cookies and storage	None
Minimum width	300px. Below 420px each drops to a single column
Dark mode	Follows the reader's system setting automatically
Height message	postMessage with `{rpEmbed, rpHeight}` from https://www.retrofitplanner.co.uk
Accessibility	Labelled fields, keyboard operable, system font stack

Frequently asked questions

Are the calculators really free to embed?

Yes, on any site including commercial ones. There is no account, no API key and no limit on page views. The only condition is that you keep the credit link under the widget.

Will they slow my page down?

No. Each widget is 18 to 33 KB before compression, all served from our own domain with no fonts, no analytics and nothing from third parties, and the snippet sets it to load lazily so it does not download until a reader scrolls near it.

Do I need to mention them in my cookie banner?

No. The widgets set no cookies, use no storage and load nothing from third parties, so there is nothing to consent to.

Can I change the colours or the wording?

Not directly, because everyone shares one copy and that is how updates reach you automatically. You can set the width and the border in the snippet, and each follows your reader's light or dark mode. Ask us on the contact page if you need something specific.

What happens when energy prices or the rules change?

We update the models and every embed updates with them, because your page loads the current version rather than a copy. The figures use the Ofgem cap for October to December 2026, heating oil at 11.3p per kWh (the BoilerJuice UK average of 116.20p a litre on 25 September 2026), a heat pump tariff of 18.7p per kWh and the Boiler Upgrade Scheme grant of £7,500, or £9,000 for oil or LPG homes with no mains gas.

Will the numbers match your own calculators?

Yes. Before any change goes live, every money figure in the heat pump widget is checked against the full calculator for all 1,800 combinations of home, heating, insulation and bill, and the EPC widget is checked on band, points, measures and total cost against the full EPC calculator for all 435,456 combinations. A reader who follows the link sees the same numbers with more detail around them.

Try the full heat pump calculator or EPC calculator, which add the carbon saving and the detail behind every number.