The winter power problem
Energy when it matters most.
How much control a building has over its energy does not only depend on how much energy it generates. It depends on when — and on whether that energy can be stored.
In winter, demand rises. Photovoltaics deliver less.
A building needs the most energy in the heating season. At the same time, photovoltaics deliver far less than in summer.
The result: dependence on the grid rises at exactly the time when power of your own would be most valuable.
The chart shows it for an example building, month by month: heat demand at the top, power from photovoltaics and from COR.gen below.
Heat demand and power generation over the year
Model calculation for an example building, values per month
With COR.boost, an immersion heater loads surplus power from the PV system and the storage unit into the buffer tank. In summer, COR.gen then hardly needs to start for hot water, if at all. COR.boost is in preparation.
Heat demand and heat generation · kWh of heat per month
| Month | Heat demand | Heat from COR.gen | Heat from COR.boost (immersion heater) |
|---|---|---|---|
| January | 4,800 kWh | 4,900 kWh | 0 kWh |
| February | 3,400 kWh | 3,300 kWh | 70 kWh |
| March | 2,200 kWh | 1,900 kWh | 330 kWh |
| April | 1,300 kWh | 910 kWh | 460 kWh |
| May | 1,100 kWh | 820 kWh | 330 kWh |
| June | 290 kWh | 0 kWh | 340 kWh |
| July | 300 kWh | 0 kWh | 360 kWh |
| August | 300 kWh | 60 kWh | 310 kWh |
| September | 410 kWh | 230 kWh | 260 kWh |
| October | 1,300 kWh | 1,200 kWh | 160 kWh |
| November | 2,600 kWh | 2,500 kWh | 130 kWh |
| December | 4,000 kWh | 4,000 kWh | 50 kWh |
Power generation and power demand · kWh of electricity per month
| Month | Photovoltaics, 10 kWp | COR.gen (heat and power plant) | Electricity demand (household and electric car) |
|---|---|---|---|
| January | 200 kWh | 1,100 kWh | 640 kWh |
| February | 430 kWh | 730 kWh | 630 kWh |
| March | 580 kWh | 420 kWh | 620 kWh |
| April | 870 kWh | 200 kWh | 600 kWh |
| May | 710 kWh | 180 kWh | 580 kWh |
| June | 1,300 kWh | 0 kWh | 560 kWh |
| July | 990 kWh | 0 kWh | 560 kWh |
| August | 850 kWh | 10 kWh | 560 kWh |
| September | 660 kWh | 50 kWh | 580 kWh |
| October | 420 kWh | 260 kWh | 600 kWh |
| November | 240 kWh | 560 kWh | 620 kWh |
| December | 220 kWh | 880 kWh | 630 kWh |
More power from COR.gen than from photovoltaics, in the model: November, December, January, February
Model calculation, not measured values. Example building: renovated detached house with 200 m² and four occupants in St. Pölten, Austria, 10 kWp of photovoltaics, one COR.gen, one COR.stor. Values rounded. Household electricity demand with one electric car (around 15,000 km a year): around 560 kWh per month in summer, 15% more in winter. COR.gen runs heat-led, mainly in the heating season. With COR.boost, the immersion heater takes over hot water in summer; without COR.boost, COR.gen starts up for it. How much power is actually generated depends on running time and building.
| Month | Heat demand | Heat from COR.gen | Heat from COR.boost (immersion heater) | Electricity demand (household and electric car) | Photovoltaics, 10 kWp | COR.gen (heat and power plant) |
|---|---|---|---|---|---|---|
| January | 4,800 | 4,900 | 0 | 640 | 200 | 1,100 |
| February | 3,400 | 3,300 | 70 | 630 | 430 | 730 |
| March | 2,200 | 1,900 | 330 | 620 | 580 | 420 |
| April | 1,300 | 910 | 460 | 600 | 870 | 200 |
| May | 1,100 | 820 | 330 | 580 | 710 | 180 |
| June | 290 | 0 | 340 | 560 | 1,300 | 0 |
| July | 300 | 0 | 360 | 560 | 990 | 0 |
| August | 300 | 60 | 310 | 560 | 850 | 10 |
| September | 410 | 230 | 260 | 580 | 660 | 50 |
| October | 1,300 | 1,200 | 160 | 600 | 420 | 260 |
| November | 2,600 | 2,500 | 130 | 620 | 240 | 560 |
| December | 4,000 | 4,000 | 50 | 630 | 220 | 880 |
Heating that generates power as well.
COR.gen, the heat and power plant inside COR.set, uses the heat demand that is there anyway: it heats with wood pellets and generates up to 2.2 kW of electricity at the same time — not in addition, but while it is heating.
Combined with COR.stor, energy is stored: 70 kWh usable, expandable to 210 kWh. That keeps the power available even when it is not needed at the very moment it is generated.
Timing makes the difference.
At 8 operating hours a day that is up to 17.6 kWh of electricity (2.2 kW × 8 h), at 12 hours up to 26.4 kWh — on days when the heating is running.
That is the calculation at rated output. The chart above calculates heat-led over the whole month: longer running times on cold days, often at part load.
How much that adds up to over a full heating season depends on your system’s running hours — we work that out for your property in the initial consultation.
- up to 2.2 kW electricity
- 92.5% overall efficiency (standard test)