A much bigger problem then is the “famous surge problem”, quite specific to UK power plants, that all the kettles are turned on after the game, royal weddings etc on Saturday/Sunday afternoons (see for example http://news.bbc.co.uk/1/hi/uk/5059904.stm), again mentioned by Tio. This problem is not so common in other countries that don’t use kettles as much. It can also be modeled stochastically, but with other parameters and with a much worse result for the power plants since the spread will be much smaller (all go on within a time frame of a few minutes so the Gaussian curve will be spiky) and the power peaks are very high (typically 1800W per kettle). Thus, the power plants already have to be prepared to start to increase production before they can actually see it happening.

Now to the main issue – admin is absolutely right concerning the “summer problem” for mCHPs. Actually, that’s how I found this post, by googling for “micro chp summer”. I also predicted that this will be a problem and it’s actually one of the biggest challenges when calculating the total ROI of investing in such a system. If the winter is really long and cold, you will save more on electricity bills, since you have to warm your home more (and vice versa of course). Further aspects are that efficiency drops during the summer months although gas costs much less compared to the winter moths. So, I concluded that it would be a fantastic investment to buy a huge gas tank, filling it up during the summer and emptying it during the winter (if it were allowed of course)!

Thanks for some great posts and an interesting discussion!

Regarding the displacement of grid power during winter – I was making the suggestion that if people replaced their gas (not electric) boilers with micro CHP units, this would reduce the load on the grid. The demand for grid electricity is highest during winter months, which coincides with when people want to heat their homes. Doing this with a CHP unit instead of a boiler would reduce demand for grid electricity more in winter months than in summer months, thus flattening out the seasonal demand curve.

Also not all micro CHP units will be replacing electric boilers, they could be replacing gas ones that don’t affect the grid, so in that case they wouldn’t be removing any load off the grid at all, although they would be helping the generation part. So again depending on whether CHPs start replacing which boilers first, this could be difficult to model. And I imagine it is likely that they will replace gas boilers first as the gas connection is already there.

In fact I was thinking that micro CHP might even make the grid more efficient since they will be used more during winter (since they are boilers) when the average load on the grid is also at a maximum. This would reduce the peak to average load ratio, thereby reducing the capacity required to ensure the system can meet peak winter demand, making the grid run more efficiently.

I agree the grid buyback price needs to be fixed carefully though to avoid people running their micro CHP units to make money!