Building thermal loads
To start the analysis you must first provide some thermal loads. Loads can be entered manually, pasted from the clipboard using the / buttons, or imported from a CSV file using the Import thermal loads button.
/ 
buttons, or imported from a CSV file using the 
Import thermal loads button.
Type of thermal load - GHE Analysis can work from the building's thermal loads — using the heat pump performance curves to derive the corresponding ground loads — or directly from ground loads obtained from a separate calculation, in which case the Heat pump performance tab is disabled.
GHE Analysis supports four input modes:
- Hourly building loads - Combined: a single net hourly load column. Loads are positive for heating, negative for cooling.
- Hourly building loads - Separate C/H + DHW: three columns — cooling, heating, and domestic hot water (DHW) hourly loads. All values are positive. The DHW demand is tracked separately and displayed as its own series on the charts.
- Hourly ground loads - Combined: a single net hourly load column where loads are applied directly to the ground (HP performance tab disabled). Loads are positive for heating, negative for cooling.
- Monthly building loads - Separate: five columns — monthly cooling demand, cooling peak, heating demand, heating peak, and DHW demand. All values are positive. Monthly energy values are converted to an equivalent hourly profile and replicated over the simulation period. If a month has simultaneous cooling and heating demand, the net demand drives the fluid temperature simulation; the dominant mode determines the peak load, applied for up to 2 hours. If the peak power multiplied by 2 hours would exceed the total net monthly demand, the peak duration is automatically reduced so that the energy balance remains exact and all base-load hours remain in the correct operating mode (heating or cooling). DHW demand is spread uniformly over all hours of the month.
When an hourly mode is selected, the table accepts 8 760 rows (one per hour of the year). When a monthly mode is selected, the table accepts 12 rows (January to December). Thermal loads are stored with a precision of 0.01 kW.
Data import - Data are pasted or imported starting at row 1; any rows beyond 8 760 are discarded, and missing rows are set to zero. The Import thermal loads button reads ordinary CSV files. The column separator — comma, semicolon or tab — is detected automatically, a header row is recognised and skipped, and European number formats (a comma as the decimal mark and spaces as thousands separators, e.g. 1 234,56) are accepted. In practice you can export a column of loads straight from a spreadsheet or energy-model report and import it without reformatting. The expected column count and order depend on the active mode:
| Mode | # Columns | Column sequence | Loads sign |
|---|---|---|---|
| Hourly modes — 8 760 rows | |||
| Hourly – Combined (+/−) | 1 | Net load | + heating | − cooling |
| Hourly – Separate C/H + DHW | 3 | Cooling | Heating | DHW | All positive |
| Hourly – Ground combined (+/−) | 1 | Net ground load | + heating | − cooling |
| Monthly mode — 12 rows | |||
| Monthly – Separate | 5 | Cool. demand | Cool. peak | Heat. demand | Heat. peak | DHW demand | All positive |
A warning is shown if the row or column count does not match expectations; missing columns are set to zero.
Domestic hot water (DHW) - When domestic hot water (DHW) loads are provided (an Hourly Separate or a Monthly mode), the hot-water demand changes the heat exchanged with the ground at each hour. The following modeling strategy is used by GHE Analysis:
- In cooling, DHW is produced by recovering heat at the condenser (desuperheating). The amount that can be recovered is bounded by the heat the cooling cycle is already rejecting to the ground, so DHW coverage can never exceed what the condenser actually produces. Recovering this heat for hot water reduces the rejection seen by the borehole field.
- In heating, DHW is produced with the spare capacity that remains once the building's heating load is fully met. If the heat pumps are already running at full output — and auxiliary heating is being called upon — no spare capacity is available and no hot water is produced by the ground-source equipment during that hour.
- In both cases, the extra electricity used to make hot water is added to the system total and is reflected in the seasonal COP. The DHW COP values used for these calculations are entered in the Heat pump performance panel.
- When a geocooling system type is selected in the GSHP System panel, the compressor is bypassed during geocooling hours. Because hot-water production relies on the compressor, no DHW is produced during those hours, and the DHW symbol is hidden from the system diagram while a geocooling system type is active.
Summary & charts: hourly load profile and demand duration curve
GHE Analysis provides a utility to visualize and analyze the thermal loads of your project. The page contains a summary showing, for cooling and heating separately: Peak hour, the hour at which the building asks for the most, space load plus hot water combined; Mode duration, the number of hours per year spent in that mode; Space peak, the highest hourly value of the space load alone; and Space energy, the annual heating or cooling energy the building asks for, hot water excluded. When the load format declares domestic hot water, two more rows appear: Total peak, the space load plus the hot water drawn at the same hour, taken at the hour that sum is highest, and DHW energy, the annual hot water demand split by the mode of each hour. The peak rows come first and the energy rows after, in the order the console's Demand coverage page uses — and Total peak and Space energy + DHW energy are exactly its two block totals. When a time step has zero building load, it is not counted in the heating or cooling hours.
Peak hour is an index into the load profile, counted from 1 like the rows of the table below it, so on an hourly step it names the row to go and read. It is not a date: the profile carries no calendar origin. The cooling peak and the heating peak never fall on the same hour, and a mode the project never enters reads —. This is the instant at which the console's whole power block is read, which is why it is stated here, next to the profile it indexes.
The top chart shows the hourly load profile over the year. Cooling loads appear in blue and heating loads in red. When DHW loads are present and a Separate mode is active, an additional orange series is superimposed showing the DHW demand. When a monthly input mode is used, the profile consists of flat plateaus representing the average monthly load for each month, each ending with a two-hour peak matching the peak value entered in the table.
The bottom chart shows the demand duration curve: cooling and heating loads are plotted as blue and red filled areas respectively, each ordered from peak to base load. Unlike the top chart, the x-axis here does not represent calendar time — it represents the number of hours at each demand level. Heating and cooling loads are sorted independently, each from the highest to the lowest value, and placed side by side: the heating segment spans all annual heating hours and the cooling segment spans all annual cooling hours. The total x-axis extent therefore equals the sum of operating hours shown in the summary panel, which is generally less than 8 760 because hours with zero load are excluded. When DHW loads are present, an orange line is added showing the DHW duration curve. The Y-axis of both charts automatically expands to accommodate the DHW peak if it exceeds the heating peak.
GHE in practice: thermal load quality and GHE field sizing
The thermal loads exchanged with the ground greatly influence the thermal response and therefore the sizing of a GHE. Under certain conditions, a 10% error on the thermal peak or on the average load can lead to a 10% error on the field size. The thermal loads used must therefore be calculated with great care and not be based on rough estimates. A few design principles deserve particular attention:
- Thermal balance of the ground. A strongly heating- or cooling-dominant building will progressively cool or warm the ground year after year. Recognising this imbalance early - and, where appropriate, correcting it - is central to a durable design. The balance can be restored on either side of the equation: on the ground side with hybrid equipment, heat recovery for DHW, or a supplemental heat rejecter; and on the building side by improving the envelope, adding solar shading, limiting heat gains or losses.
- Peak versus energy. The peak load governs the worst-case fluid temperature and the short-term safety of the system, while the annual energy balance governs the slow drift of the ground temperature over the system's life. Both matter, and a field sized for one can disappoint on the other.
- Realistic profiles, not rules of thumb. Equipment rarely operates at its rated block load. Diversified, hour-by-hour profiles that reflect occupancy, ventilation schedules and the simultaneity of zones give a far more honest picture of what the ground actually experiences than a single design-day figure.
- Part-load reality. A GSHP system spends most of its hours operating well below peak. Loads that capture this part-load behaviour, rather than a handful of design-day values, lead to sizing and energy estimates you can defend to a client or reviewer.
In short, the quality of a GSHP system design is bounded by the quality of the loads it starts from. Time invested in a credible load profile is repaid in a field that is neither undersized - and at risk of breaching its temperature limits - nor oversized and uneconomic.