Building energy efficiency – class, consumption, costs and emissions

A building’s energy efficiency is often discussed as a single letter: this house is class C, the neighbour’s is class B. The letter matters, but it is only one dimension. Energy efficiency is worth looking at from at least five directions: the calculated class on the energy certificate, other ratings, actual consumption where the building stands, running and maintenance costs, and emissions. They do not always point the same way. In this article we go through the dimensions and explain why an energy renovation is usually best timed for when the old equipment is nearing the end of its service life.

What does a building’s energy efficiency mean?

Dimension	What it describes	Where to find it	What it does not tell you
Energy certificate (E-value and energy class)	Calculated purchased energy under standardised use, weighted by energy carrier	The energy certificate	Actual consumption, the energy bill or maintenance costs
Other ratings (e.g. LEED, BREEAM, Nordic Swan Ecolabel)	Environmental and quality factors more broadly; energy is one part	The rating's certificate	Anything about buildings that have not been rated – most residential buildings have not
Actual consumption	How much energy the building really buys in its own climate and use	Energy bills and consumption monitoring	How much of the consumption is down to the building and how much to the occupants
Running and maintenance costs	The price of energy, servicing, inspections and equipment replacement	Bills, service log, maintenance plan	The building's comparable efficiency
Emissions	Emissions from energy use and the manufacturing carbon footprint of equipment	Energy companies, Motiva, emission databases	The energy bill

What does the energy certificate measure?

According to the Ministry of the Environment’s definition, the E-value on the energy certificate is “a calculated energy efficiency reference figure that allows buildings to be compared on the basis of their standardised use”. Three things make it a reference figure rather than a consumption forecast:

Standardised use. The calculation uses standard values for the building’s purpose: indoor temperature, ventilation, hot water use, and the use of appliances and lighting. The occupants’ actual lives do not affect the figure.
The same weather everywhere. The weather data used is that of Helsinki-Vantaa, whether the building is in Hanko or Sodankylä.
Energy carrier factors. Purchased energy is weighted with factors: currently 1.20 for electricity, 0.50 for district heating, 1.00 for fossil fuels and 0.50 for renewable fuels used in the building. Heat a heat pump takes from the ground or the outdoor air is not purchased energy, so it lowers the E-value.

On 8 October 2026 the Government issued separate factors for zero-emission buildings, 25 per cent lower than the current ones except for fossil fuels, which can be used from 1 January 2027. The current factors remain in force for nearly zero-energy buildings, and for now the energy certificate of an existing building is still calculated with them – more in energy carrier factors 2027.

Based on the E-value, the building is placed in an energy class from A to G on a scale specific to its purpose. A new or renovated zero-emission building may in future also use the designation A0. Because of the factors, the same E-value can mean very different amounts of purchased energy. Our own calculation for a 140 m² house with an E-value of 200: fully electrically heated, it corresponds in the calculation to about 23,000 kWh of purchased electricity a year; with district heating, to about 49,000 kWh of district heat plus the household electricity. So the energy class does not tell you how much energy or money the house uses. It tells you how the house ranks against similar buildings calculated by the same rules.

We go through the calculation step by step in the article how a house’s energy class is calculated, and you will find the class limits in building energy classes.

What do other ratings measure?

The energy certificate is the only mandatory rating. Alongside it there are voluntary environmental ratings, which according to the Ministry of the Environment’s terminology describe a building’s environmental performance “on the basis of its location, its use of water, energy, raw materials and natural resources and its other environmental impacts”. Energy is therefore only one area among several.

Rating	Run by	What it assesses	Typical buildings in Finland
LEED	U.S. Green Building Council	Energy and water use, materials, waste, indoor environment; levels Certified to Platinum	Offices and commercial premises, now also homes
BREEAM	BRE (United Kingdom)	Energy, water, materials, health and wellbeing and management, among others; BREEAM In-Use for buildings in use	Commercial premises; most certifications in Finland are for buildings in use
Rakennustieto environmental rating (formerly the RTS environmental rating)	Rakennustieto	Carbon footprint, energy and material efficiency, the construction site, indoor climate; 1–5 stars	Blocks of flats, schools, day care centres and commercial premises; in the project phase also detached and terraced houses
Nordic Swan Ecolabel	Ympäristömerkintä Suomi (Ecolabelling Finland)	Among others, energy use in operation at least 10 % below a nearly zero-energy building, moisture management, harmful substances	New detached houses and blocks of flats, public buildings; separate criteria for renovation

A rating says more about the building’s quality than the energy certificate does, but most residential buildings do not have one, and the results of different ratings cannot be compared with each other.

How do you find out a building’s real energy efficiency?

Real energy efficiency shows in actual consumption: how much energy the building buys where it stands, with the people who live in it and in the condition it is in. Climate, indoor temperature, ventilation settings, hot water use and the condition of the equipment all affect it. In a housing company’s block of flats, heating domestic hot water takes 20–30 per cent of the purchased heating energy according to Motiva, and the amount depends largely on how much water the residents use.

The energy certificate records the actual purchased energy for the previous full calendar year, but it is not corrected for the weather, and according to the certificate’s own text it cannot be compared with the calculated consumption. So it is worth monitoring your own building yourself:

Normalise the heating energy. A mild winter lowers consumption without the building getting any better. Normalisation converts the space heating energy to the level of a normal year using heating degree days: normalised consumption = actual consumption × heating degree days of the normal year / heating degree days of the actual period. Domestic hot water heating is removed first, as it does not depend on the weather. The Finnish Meteorological Institute publishes heating degree days by locality, and the normal year is the average of 1991–2020. For example, if the heating degree days were 90 per cent of normal, 15,000 kWh of actual heating energy corresponds to about 16,700 kWh in a normal year (our own calculation).
Compare years with each other. Normalised consumption tells you whether the building is improving or getting worse. Once the effect of the weather has been removed, the cause of a sudden rise lies in the building or its use, for example a fault or the settings.
Compare with similar buildings. Dividing consumption by square metres or cubic metres lets you compare it with buildings of the same age and type. In Motiva’s method, buildings in different localities are compared using a correction factor for a common reference locality.

Running costs: the energy bill is not the whole price

Energy efficiency shows in the energy bill, but the total cost of heating also includes servicing, inspections and replacing the equipment at the end of its service life. Here heating systems differ more than the energy class reveals:

Heating system	Purchased heating energy, Motiva's 2024 example house	Technical service life according to Motiva	Regular maintenance
Ground source heat pump	€910/yr	Pump about 15–20 years; a correctly sized collector circuit is long-lived, on the order of the house's service life	Strainers cleaned every year and collector circuit pressure monitored; professional servicing every 3–5 years
Air-to-water heat pump	€1,240/yr	About 15 years	Dirt separator cleaned every year, outdoor unit kept clean; professional servicing every 2–5 years
District heating	€1,840/yr	Heat distribution centre 20–25 years	Visual leak checks and checking that the controls work; according to Motiva it needs comparatively little maintenance
Water-based electric heating	€2,720/yr	No official figure	No compressor or refrigerant circuit; Motiva advises replacing a circulation pump older than 15 years
Oil heating	€3,050/yr	Boiler about 25 years, burner about 15 years	Motiva's calculation assumes maintenance costs about €200/yr higher than for ground source heat, an air-to-water heat pump or district heating

The purchased energy costs are from Motiva’s calculation for a small 1990s detached house at March 2024 prices (electricity 16 c/kWh).

A heat pump reduces purchased energy the most because it moves heat from the ground or the air. That is exactly why its design is more complex than an electric boiler or a district heating distribution centre: it has a compressor, a refrigerant circuit and control electronics, plus a collector circuit or an outdoor unit depending on the type. The complexity shows in the costs in three ways:

Servicing. Owners can carry out routine upkeep themselves, but according to Motiva’s maintenance guide the actual servicing is ordered from a company holding a refrigeration equipment business certificate from Tukes (the Finnish Safety and Chemicals Agency), and professional basic servicing is recommended every few years. For example, for servicing an air source heat pump in a detached house you can get the household expenses credit on the labour share.
Statutory leak checks. If the equipment contains at least 5 tonnes of CO₂ equivalent of fluorinated greenhouse gases, the tightness of the refrigerant circuit must be checked at least every 12 months, and more often for larger charges. Hermetically sealed equipment in residential buildings containing less than 3 kg is exempt from the checks. The charge is marked on the equipment’s rating plate. According to Motiva, the statutory requirements grow with larger heat pump systems, so in a housing company project the checks belong in the cost calculation.
A shorter service life. A heat pump is replaced roughly every 15–20 years, a heat distribution centre every 20–25 years. With ground source heat, replacement concerns the pump, not the borehole, but Motiva points out that a more efficient new pump may draw more energy from the borehole than the old one.

A heat pump can still be very profitable: in Motiva’s examples, replacing oil heating with ground source heat pays for itself well within the pump’s service life. The starting point decides. If the same example house already had district heating, the energy saving from ground source heat would be about €930 a year (our own calculation: €1,840 − €910), and it would have to cover the investment, servicing and replacing the pump. The energy certificate does not see these costs: a heat pump improves the E-value, but the figure says nothing about maintenance. So compare the options on their total costs over the full service life. We have gone through the options for an electrically heated house in energy renovation of an electrically heated house.

Emissions: energy use and the carbon footprint of new equipment

The emissions from energy use depend on how the energy is produced. According to Motiva, the average emission factor of Finnish electricity in 2022–2024 was about 45 kg CO₂/MWh and that of district heating about 115 kg CO₂/MWh (domestic production, combined heat and power allocated with the energy method). District heating emissions vary a lot between localities, however, so your own energy company’s figure tells you more than the average. The energy carrier factors are not emission factors: according to the Ministry of the Environment, they steer towards energy-efficient construction and sustainable use of natural resources. That is why electricity weighs more than district heating in the E-value, even though electricity’s average emissions per megawatt hour are currently lower. The energy class and the carbon footprint are different things. More on the factors in energy carrier emission factors.

New equipment also causes emissions before it heats the house. According to CO2data.fi, Finland’s emissions database for construction, manufacturing an air source heat pump typically causes about 14 kg CO₂e per kilogram of equipment, mainly from the refrigerant. The database takes the unit to weigh 50 kg, which puts its manufacturing emissions at about 700 kg CO₂e – the same as the emissions of about 15 MWh of average Finnish electricity (our own calculation). According to the Finnish environmental administration, the fluorinated greenhouse gases used as heat pump refrigerants are gases with a strong warming effect on the climate, and their emissions arise when equipment is manufactured, used and decommissioned. A tight refrigerant circuit is therefore also a climate matter.

Since January 2026 there have been limit values for the carbon footprint of new blocks of flats and terraced houses; they do not apply to renovations or detached houses. More in climate report.

When is it worth investing in energy efficiency?

Usually when the old equipment is nearing the end of its technical service life, or when the building is being renovated anyway. According to the Ministry of the Environment, energy-saving repairs are often not cost-effective when carried out on their own; the opportunities arise when a building is repaired for another reason – and the energy efficiency of technical systems is improved when they are replaced. Equipment service lives tell you when the moment comes: according to Motiva, an oil or gas boiler lasts about 25 years, and replacement is worth considering once it is over 20 years old. According to guidance from Finnish Energy, it is not worth renewing individual parts of a heat distribution centre that is more than 20 years old; it is renewed as a whole. There are four reasons for the timing:

Only the price difference is an energy investment. When the old equipment has to be replaced anyway, the replacement costs money anyway. Only the price difference to an ordinary replacement then counts as the investment in the more efficient option, and the payback time gets shorter.
The remaining value of working equipment is not wasted. If five-year-old equipment is replaced, its remaining service life and manufacturing emissions are thrown away, and the manufacturing emissions of the new equipment arise years early.
The work is combined. Additional insulation is cheapest during a facade or roof renovation, when the scaffolding is up and the structures are open. In renovation that needs a permit, energy efficiency must be improved where this is technically, functionally and economically feasible – more in energy report for renovation.
Planning ahead leaves time to compare. When equipment breaks down in the middle of winter, it is replaced with whatever can be installed fastest. When the replacement is planned, there is time to calculate and tender the options. In a housing company, the timing belongs in the long-term maintenance plan – see housing company energy renovation.

Fossil heating is the exception: according to Motiva, giving up oil or gas heating is one of the most important climate actions a household can take, and the increased household expenses credit for giving up oil heating is available until the end of 2027. Then it can pay to bring the switch forward – see ground source heat grants and energy renovation.

How to assess your own building’s energy efficiency

Look at the energy certificate. Check the class and whether the certificate is still valid with our energy certificate check tool. For data protection reasons, certificates of detached houses do not appear in the public search, so choose “Add your own energy certificate” in the tool.
Collect three years of consumption and normalise the heating energy for the weather.
List the equipment, its age and its servicing. The service log or maintenance plan shows what is due for replacement in the coming years.
Compare the options’ total costs: energy, servicing and replacement over the full service life, not just the energy bill.
Time the change for the end of the equipment’s service life or alongside other repairs.

We prepare energy certificates and E-value calculations that show how different options affect the energy class before you decide. Detached house owner: submit a request for a quote. Housing company: ask for an estimate.

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