Not so Eco and not so cute

The electricity bill for the month of March just came through, and the good news is that we only used 147 kWh. The bad news is that we were away for all of the covered period--23rd February to 25th March--so most of this energy was being used while we were out of the house. Maybe not a big deal in the grand scheme of things. This only added about 1800 yen to our electricity bill, which is little compared to the repayments on the loan, or on the amount they are paying us for our solar electricity generation, which was 45,000 yen for the same period. 

It seems a lot compared to last month when we were in and used 573 kWh. 25% in fact. 29 kWh were used in at-home time, and 117 night time. Only one kWh was used during day time, but this is not surprising as the panels will have been producing electricity for most of this time.

At-home time is 7 am to 9 am and 5 pm to 11 pm; 8 hours per day. For the 32 days, that's a power consumption of around 110 Watts. Night time is 11 pm to 7 am, also 8 hours, and you'd expect the same consumption, but it averaged 460 Watts. The only difference is the eco cute, programmed to come on at night.  Taking 110 Watts as the background consumption of the house, mainly the ventilation system and the fridge, which we left running, but also the circuitry and leds on display panels, and maybe some phantom consumption on the light bulb sensors, that means the eco cute used 88 kWh over the month. That's almost 3kWh per day, and we didn't use any hot water, and the underfloor heating was switched off. The energy it was using was just making up for the heat it was leaking into the house.

I'd set the tank to low temperature while we were away, but when we came back the display said it had one bath and 50 minutes of shower. I suppose this is less than one bath and 90 minutes of shower that it usually has, but this still seems to be a lot of heat. The exact meanings of the high, medium and low temperature settings are far from clear or explicit, and it seems like it's impossible to set them to actual temperatures, for example having the water in the tank at 50 degrees. Also, having thought that I could vary the amount of hot water in the boiler, it suddenly clicked that the setting of full tank, 50 litres or 100 litres is just for the amount of hot water it will add to the tank when you press the re-heat button. It doesn't make any difference to the amount of heat in there.

Without knowing the COP of the heat pump, it's difficult to know exactly how much heat this represents. I can maybe get some ideas by looking back over the temperature each night, and the electricity consumption data, and work out the relationship between the two, assuming that it's losing the same amount of heat each day from the constant set temperature of the tank (whatever that is) to the more or less constant temperature in the boiler room. Heat loss is proportional to temperature difference.

In a way this is the worst possible conditions for heat loss, as the tank was left full. But it was set to the lowest setting, and the boiler is inside. Imagine the usual situation where the boiler is outside, and it is left set to high. 

And they all lived happily ever after...

Actually the lack of posts for the last few weeks has been because we've been away in the UK, concentrating on family and friends rather than work and house building. There are still several issues unresolved, ongoing and upcoming. Regular blogging service will resume shortly.

The big window is still not right, and I believe Pazen made a serious design flaw with the hinge.

We still haven't got any blinds or curtains in, or put pictures up on the walls.

Electrical generation is hopefully going to keep coming and it would be really nice if the data could be accessed electronically rather than having to write everything down from the display.

It's going to take a couple of years to work out exactly how much we will need the heating in winter.

The thermal performance of the house will take at least two winters and two summers to get a proper grasp of.

And I need to sort out the photos. 

The good news is that we got back to the house and it was still fairly warm after a month of winter with no heating on. The middle of the slab had cooled to 17 degrees. It was freezing outside.

Eco con

During the explanation session, I asked the plumber about changing the temperature of the boiler, which he said was impossible. In fact, checking the manual and playing with the controls, I found that it was possible. There are three settings for boiler temperature: high, medium and low. Also, there are three settings for the amount of hot water in the boiler: a full tank (460 litres), 100 l or 50 l. 

The plumber didn't actually fit the boiler, so I don't completely blame him (although he shouldn't be telling people things are impossible when he just doesn't know how to do it), but the people who did fit the boiler also put in the underfloor heating, which they switched on to pump hot water through
the whole time, and did not set the boiler to the maximum temperature, so it was both using expensive day time electricity, and running out on us when it came to bath time. So they didn't know how it worked either!

I suspect there are many people, like my parents-in-law for example, who are producing way more hot water than they need and have not been told how to set their boilers properly. The Passive House lady considers this to be a serious national problem, causing massive excess energy use, and a lot of disgruntled customers.

The idea behind the Eco Cute is basically to use cheap night time electricity, from 24-hour nuclear and gas-fired power stations, and not really anything to do with ecology or saving people money. 

People with large households certainly get a good deal with their Eco Cutes, providing they don't run out of hot water. Meanwhile a lot of elderly couples, victimised by silver-tongued salesmen, find that their heating bills go up, on top of the investment of their savings into this new wonder, or worse still having been encouraged to take out a loan to pay for it. Over-dimensioned tanks with insufficient insulation incorrect settings.

The situation in Hokkaido is apparently that so many people are using Eco cutes that there is now a shortage of night time electricity.

Not sure if it's Eco, or cute, but it can certainly do wonders with hot water

The fancy display panel on the wall next to the kitchen allows us to set the tap temperature anywhere between 35 and 60 degrees, and the clever control system will mix the water from the boiler, at a much higher temperature, with cold water to get us what we want.

The bath can be set to fill automatically to a range of heights and temperatures although only up to 48 degrees. So we can't use the bath for making soup.

The system is very intelligent. We tried to fill up the bath with the plug out the other day and very quickly the eco cute realised our mistake and switched off the water.

In our old house about once or twice every week we would either leave the water running so that it was spilling over the top, overheat the bath so that we needed to throw hot water away before we got in, or both.

Little bars on the display panel show us how much hot water is available from the tank. One bar for 50 litres at 50 degrees. 2 bars for 100 l, 3 bars for 150 l, 4 bars for 200 l and 5 bars for 300 l or more. With a 460 l tank, with water over 60 degrees, there will be a full five bars with just half the heat capacity of the tank. I'm having trouble finding in the manual exact temperatures for the high, medium and low temperatures the boiler can be set at, but in the spec at the end, it gives a range of 65 to 90 degrees.

As well as the bars, the display panel will show how much hot water there is, measured in number of baths and minutes of shower. I think it measures a bath as around 30 minutes of shower. At full tank, I've seen it gives one bath and 95 minutes shower, so it doesn't count in multiple baths. That wouldn't make sense in a communal bathing culture, as you can only have one bath.

There's a display panel in the bathroom, but this just shows how many minutes of shower are left. I suppose if you're in the bath, you won't be interested in how many baths there are, as you already have one, and if you're having a shower, you won't want to have a bath. I keep meaning to compare the number of minutes shower on the bathroom panel with the number of baths and minuts shower on the panel down stairs to get a more precise relationship between baths and minutes shower, but haven't managed yet. Anyway it wouldn't be that precise because the number of minutes shower is only to nearest five.

Everything works really well, but it's very difficult to find exact data, for example how hot is the water in the tank? How much is there? How much hot water did we use each day? 

The machine knows a lot of this, and when the temperature is set to "medium", it is looking at how much water we've been using, and heating the water appropriately. Maybe it's just me, but I'd like to know that information too!

Getting into hot water

The heating system was fixed a couple of weeks after we moved in, and we have a panel on the wall under the stairs to adjust it. For all that we're trying to build a house that doesn't need a heating system in a country where houses traditionally don't have them, we seem to have done just that.

I think this is the first house in Japan I've lived in that has plumbed hot water and it's certainly the first house with any kind of central heating system. It's very European in the sense that it effectively has a boiler with a supply of hot water for washing and also for heating. For a day or two our boiler was running out of hot water, but this was because the heat was all being sent under through the pipes under the floor.

Hot water running out is something that anyone who has lived in a boiler culture will be aware of. My wife has never forgotten getting in trouble for using all the hot water when we were staying in a bed and breakfast before my brother's wedding. 

The concept of hot water running out is perhaps alien to Japan. Japanese has a separate word for hot water "o-yu" rather than "mizu", which it is tempting to argue is due to the abundant natural availability of hot water in the country. In many places it simply flows out of the ground. Hot spas spring up in the middle of cities, and clusters of hotels burst out around them in the countryside, in the mountains or by the sea.

Although this is the first house I've lived in with plumbed hot water, every house I've lived in has had running hot water, and copious amounts of hot water available in the bath. The first house I lived in had no running water in the bathroom, but you could fill the bath with water, and then heat and reaheat that. You could heat the bath a little, then you'd get some hot water at the top which you could scoop out for a shower. When she was a kid, my wife used to have to build a wood fire under the bath at her house. So there was a very visible body of water there. 

All the kitchens where I've lived have had a gas geyser that will produce hot water into the sink on demand. Instant hot water that only runs out if the gas is not connected, or if the battery goes in the geyser and the sparks stop working. 

Meanwhile, at around the same time my wife was loading wood to fire her bath a quarter of a century ago in the mid 1980s, I remember on my first stay in Tokyo seeing somebody going to a pay phone and dialling in some numbers without saying anything. He was setting his bath to come on so that it would be ready when he got home. His bath was electronically controlled to supply and heat the water, and the controller was connected to his answer phone, which could take remote instructions.