Estimate heating and hot-water demand (MIS 3005)

Before you size a UK heat pump you need a defensible demand figure, and MCS wants it worked to MIS 3005. Reonic works it out from the heat loss you have already built for the building and the answers you give in the estimate form.

Before you start

• The job is a UK heat-pump design with an air-source heat pump. The estimate supports air source only.
• Build a heat-loss basis for the building. The estimate saves only when the building has one of these: an EPC check, building from properties on the Building card, or a room-by-room heat load calculation.
• Have the form answers to hand: the main heating fuel and its energy price (p/kWh), the number of bedrooms and residents, the emitter type, the system purpose, the design flow temperature, the pasteurisation strategy and, for immersion pasteurisation, the proposed cylinder size.

Produce the estimate

1. Open the offer in the Reonic Portal.
2. Go to Planning and open the Building card.
3. Find Generate heat pump performance estimates (MCS MIS 3005).
4. Click Start. If an estimate already exists, the button reads Edit and the card shows a Completed tag.
5. In MCS Heatpump Performance Estimate, check the two fixed fields. Heat pump type is set to air source and Is the system type hybrid? is set to "No".
6. Select the Main fuel of heating (Coal, Electricity, Gas, Lpg or Oil). The field carries the hint "Given by MCS based on your address".
7. Enter the Energy price (p/kWh).
8. Enter the Number of bedrooms.
9. Enter the Number of residents.
10. Select the Emitter type. Unless you choose existing or mostly upgraded radiators, also select the Type of underfloor heating.
11. Select the System purpose.
12. Select the Design flow temperature, from "Up to 35 °C" to "61-65 °C".
13. Select the System pasteurisation strategy. For an immersion strategy, also enter the Proposed cylinder size (L).
14. Save the form.
15. Use the figures when you choose the heat pump.

The results show:

• Energy required for space heating and energy required for hot water, each with the demand to be supplied by the heat pump, and the calculated daily hot water demand.
• Your postcode prefix, the total property floor space and the average watts per square metre.
• The heat pump capacity, the heat pump type, what your system is proposed to provide, the proposed heating system, the proposed flow temperature and the Seasonal Performance Factor.
• The high/low energy consumption estimate of the heat pump.
• The "Important Note" and any "Applicable warning notes".

Read the calculation

The estimate starts from EPC data and is refined once the room-by-room heat load (BS EN 12831) is complete.

• Peak heat loss comes from the room-by-room or building-from-properties heat loss when one exists. Otherwise Reonic derives it from the EPC's annual space-heating demand, using the location's heating degree days and a 21 °C design temperature. Heat pump capacity is that peak heat loss divided by 1,000. The info popover on the capacity says the figure is indicative unless a full heat loss calculation was done.
• Average watts per square metre has an info popover to help you read it: 0–30 W/m² is very low heat loss and 120–150 W/m² is very high.
• Daily hot water is 45 L multiplied by whichever is higher: bedrooms + 1, or the number of residents (MIS 3005-D V3.0 §5.6.2).
• Annual hot-water energy comes from the EPC when there is one. Without an EPC, Reonic calculates it with the SAP 10.3 energy-content formula and monthly cold-water temperatures, and an info popover tells you so.
• The Seasonal Performance Factor is set by the design flow temperature band, not by the heat pump's catalogue data.
• ≤35 °C — 4.0
• 36–40 °C — 3.8
• 41–45 °C — 3.4
• 46–50 °C — 3.1
• 51–55 °C — 2.8
• 56–65 °C — 2.5

Hot water uses an SPF of 1.9 (MCS-031-a §2.5(n)).

• Immersion pasteurisation adds energy. Daily or weekly immersion adds 10 K × 4,200 J/kg·K × the cylinder litres for every cycle. A warning note appears if no cylinder size is recorded.
• High and low consumption are the total plus or minus 10%. The warning notes are chosen by heat-loss band (W/m²), emitter type, flow temperature and underfloor type.

Things to know

• Some fields come pre-filled. System purpose defaults to space heating and hot water, and the pasteurisation strategy to "by heat pump". The design flow temperature is pre-set from the room-by-room calculation when one exists. Bedrooms and residents come from the room-by-room or building-from-properties data.
• Missing inputs show a message. Without a heat-loss basis you see "Please complete the EPC check, building from properties, or room-by-room heat load calculation before running the MCS performance estimate." If some inputs are still missing you see "Some results are incomplete. Complete the EPC check or room-by-room heat load calculation to get full results."
• The estimate informs your sizing and leaves the selection to you. Carry the capacity into the heat-pump selection yourself.
• Use UK MCS values on a UK job. When you enter the heat pump's values, check that they are the UK MCS ones.

Last updated on November 9, 2026