What determines your energy label? The six factors explained
Your energy label is not a grade for how new your house is, but a measurement of how much fossil energy your home needs per square metre per year. Six factors together determine where you land between A and G: the glazing, the walls, the roof, the floor, the heating and your solar panels. In this blog we walk through all six, explain what weighs heaviest, and you can calculate it free for your own home right away. We arrange an official label from € 220.
How is an energy label calculated?
A certified advisor surveys the home and uses the legal NTA 8800 method to calculate how much fossil energy the home needs, expressed in kilowatt hours per square metre per year. That single number determines your letter: an efficient home sits below roughly 160 kWh/m² (label A), an inefficient one above 380 (label G).
Important to know: the calculation does not work with points or fixed percentages, but with the actual properties of your home. And anything you cannot prove is calculated with the standard value for the construction year - usually the least favourable assumption. That is why evidence pays: an installer's invoice can easily make a class of difference.
Factor 1: the glazing
Windows are the weakest spot in your envelope. Single glazing loses almost three times as much heat per square metre as HR++ glazing - and since an average home quickly has twenty per cent glazed surface, the jump from single to HR++ is often the biggest single improvement there is. From standard double glazing to HR++ the gain is smaller, but still worthwhile.
Note: double glazing with a heat-reflecting coating already counts as HR glass in the calculation. The advisor reads the type from the code on the spacer between the panes.
Factor 2: the walls and the cavity
Homes built after 1975 almost always have an insulated cavity from construction. For older homes the question is: was the cavity ever retrofilled? You can tell by rows of small, sealed drill holes in the joints of the outer wall. Filled and provable means a solid step; empty or unprovable means calculating with the low standard value of the construction year.
Pre-war homes often have no cavity at all. There are still options (internal or external insulation), but they only count when visible or provable with an invoice.
Want to see how this factor works out for your home? Our free energy label calculator retrieves your construction year and floor area from the Dutch building registry and asks exactly these six things. Within a minute you see an honest indication with a range.
Factor 3: the roof
In a ground-level home the roof is one of the largest surfaces of the entire envelope - and heat rises, so this is where you lose a lot. Roof insulation is relatively easy to prove: the advisor often simply sees the insulation material in the attic or under the roof tiles. An insulated roof combined with good glazing already lifts many post-war homes towards label C or B.
Factor 4: the floor
Floor insulation is comfortable (no cold feet) and certainly worthwhile, but for the label the floor weighs less than people think: the ground under your house provides some insulation itself. The official calculation therefore counts heat loss to the ground in a damped way. Rule of thumb: glazing, walls and roof first, then the floor.
Factor 5: the heating
How you make the heat counts just as much as how you keep it in. An old conventional or VR boiler wastes up to a quarter of the gas that a modern HR-107 boiler uses effectively. A hybrid heat pump is a solid step above that, and a full heat pump the biggest: it uses no gas at all and extracts three to five kilowatt hours of heat from every kilowatt hour of electricity.
The survey looks at the make, type and year of your unit - so have those details ready. With a heat pump the emission system also counts (underfloor heating performs better than small radiators).
Factor 6: solar panels
Here is a surprise: solar panels are the strongest single lever in the calculation. Every generated kilowatt hour counts directly as a saving on your energy use, no ifs or buts. Every panel counts, and the effect is linear: twice as many panels means twice the label gain. For reasonably insulated homes a full solar roof is regularly the difference between label B and label A - or between A and A++.
Want to dig deeper? Also read our blog on solar panels and your energy label →
What weighs heaviest?
Online you will find confident percentages ("insulation counts for 35%"). They appear nowhere in the official calculation method. The honest order depends on your home:
- 🏠 Your home type sets the proportions. A terraced house has little wall surface (the neighbours insulate with you), so glazing and roof make the difference there. A detached house loses most through its walls.
- 🔑 The starting point is your construction year. Anything you cannot prove is calculated with the standard value of the building period - which is why untouched older homes score low.
- ☀️ The biggest single jumps: from single glazing to HR++, having an empty cavity filled, and installing solar panels. Replacing the heating with a (hybrid) heat pump follows right behind.
Calculate it for your own home
Exactly these six factors are the six questions in our free energy label calculator. Enter your postcode and house number (construction year and floor area come automatically from the building registry), click through the six questions and within a minute you see an honest indication with a range on the A to G bar. Free, and you leave no data behind.
Good to know: it remains an indication. Since 2021 no valid energy label exists without an on-site survey - the advisor must be able to see or verify insulation. Need a valid label for selling or letting? We arrange it from € 220 →
For estate agents and landlords
Want a quick sense of where a home or a portfolio roughly stands, before any survey? Use the calculator as a first sieve and look up the registered label via EP-online →. For landlords the label also weighs heavily in the WWS rental points - one class of difference can noticeably shift the maximum rent.
Frequently asked questions
How is an energy label calculated?
A certified advisor surveys the home and uses the legal NTA 8800 method to calculate how much fossil energy the home needs per square metre per year (kWh/m² per year). That number determines the letter: the lower the consumption, the better the label.
Which factors count towards the energy label?
The most important are the glazing, the insulation of walls, roof and floor, the heating system and solar panels. The construction year (for anything that cannot be proven), airtightness, ventilation and the home type also weigh in.
Is it true that insulation counts for a fixed percentage?
No. You will find percentages online such as “insulation counts for 35%”, but they appear nowhere in the official calculation method. How much a measure matters differs per home: a terraced house has little wall surface, for example, so wall insulation weighs less there than in a detached house.
Can I calculate my home's energy label myself?
You can calculate a free indication with our online tool: enter your address, click through six questions and you instantly see an estimate with a range. A valid label for selling or letting does require a survey by a certified advisor since 2021.
What does an official energy label cost?
At Hollands Duurzaam from € 220 including VAT, the home survey and registration in EP-online. The price depends on the home type; an apartment starts at € 275 and a detached house at € 375.
Request an energy label?
No valid label found, or want it in black and white? At Hollands Duurzaam you arrange an official energy label from € 220 - BRL 9500-MWA-W certified, calculated under NTA 8800, and registered in EP-online, so valid again for ten years. Much cheaper than a fine and usually ready within a few working days. We work in Woerden, the Groene Hart, and across the Randstad.