Good morning, and welcome to this conference call for the second quarter of 2019. My name is Susann Linde. I am CFO and Head of Investor Relations here on Wallenstam. There will be a letter icon here, down under on this presentation where you can click if you have any questions. We will also translate the Swedish questions and put them on our webpage after that. Now turn to page two and talk about some important events for this second quarter. The most important is that we follow our plan and the business is growing as planned. If I shall mention something, we have established a framework for green bonds under this quarter, and it is under our existing MTN program, and it has been reviewed by CICERO and obtained the highest rating, Dark Green and Excellent .
In May, we also issued the first green bond within this framework of SEK 500 million with a maturity of two years and a variable interest rate of three months STIBOR plus 75 basis points. The bond was also listed on the Nasdaq Stockholm Sustainable Bond Market. On April 1st, we took the commercial property on Vasagatan 45 into possession. It is 7,000 sq m. T he same date, Jämtkraft took over our electricity customers. One thing that is very important is that we are still self-sufficient in renewable energy after this. We own our 66 wind turbines. Convendum is expanding in Umami in Sundbyberg. We have another contract there of 5,000 sq m already, and in this second quarter, we have a new letting of 6,200 sq m for a conference center, a corporate housing, and a Big Office, which is a unique all-inclusive office concept.
In total, they will let 11,200 sq m here in this area and the occupation will occur gradually during the start of 2020. Now turn to page three. This is the map where we have our investment properties at a value of SEK 49 billion. As always, we are situated in the most growing areas in Sweden, Stockholm, and Gothenburg. We have 9,100 apartments in our management, and 4,000 of them are in Gothenburg and the rest in Stockholm. We have also 1,000 commercial tenants. Now turning to page four. I will start to talk a little bit about our results and start with the NOI. It has increased by 7%, and the rental income is just about SEK 1 billion for this half year. On the next page five. You can see how efficient our property portfolio is.
It will be gradually more efficient because we occupy our new construction, which are completed, and it contributes to a more efficient property holding. Of course, our work with existing properties, for example, energy efficient projects and successful lettings, also contribute to efficient property. Now turn to page six. As I said, the NOI is 7% up compared to last year, and it is SEK 50 million, out of which the rental income is SEK 59 million, where the construction is the main part. We have no completions during this half year, which means that the contribution comes from the one which we have occupied or completed from [2018] last year and to this date. SEK 23 million is from our existing properties where we still see a strong commercial market, which has increased by almost 6% in existing holding.
Because of increased property tax, we invoice the most of it, which affects the rental income, but also the operating expenses with almost the same amount. The operating expenses are SEK 9 million higher compared to last year, and the main reason is the bigger property holding. We have also been affected by increased tariffs regarding, for example, water and sanitation. Because of new accounting rules, we recognize the site lease programs as a financial expense from January 1st of this year. So in total, it's an NOI increase by SEK 50 million. Now turn to page seven. Th e commercial market is very strong, like I said, and here are some key figures. The net lettings increased by SEK 1 million this first half-year, and this is the difference between new leases and lease terminations.
The renegotiations which we made this first half-year resulted in increased rents of on average 7%. It is still a strong commercial market, and the vacancy is still 3%. Now turn to page eight. In total, the income from property management increased by 18%, SEK 85 million. The administrative expenses are not higher in total in the group, but here in this income from property management, it's up SEK 4 million. But in total in the group, it's a zero-sum game. The financial expenses are SEK 40 million lower compared to last year. The average interest rate during the period is 50 basis points lower, and one reason is that we realized our interest rate derivatives last year in May and went into new ones at a lower interest rate level. The financial expenses are also affected negatively by site leasehold rents of SEK 6 million.
Now turn to page nine. D uring the first quarter, we expanded our fixed interest term with new derivatives of SEK 1.5 billion with a maturity of 10 years, but no new ones this second quarter. We have a fixed interest term of 41 months, an average interest rate of 1.19% during this half-year period. We have invested a lot during this half-year, which also affects the interest-bearing liabilities, which have increased by an average SEK 2 billion compared to last year. We are still mainly financed, as you can see here on the graph, through bank loans, almost 70%. 10% of our funding is green. We have the bond of SEK 500 million and also green bank loans of SEK 1.8 billion. Now turn to page 10.
Li ke I said in the beginning, we are still self-sufficient in renewable energy through our 66 wind turbines. Here you can see that the income from natural energy have a decrease of SEK 23 million, if you look here in this income statement. But if you look in the segment report, we will report how we follow the business. The hedging of the energy prices is considered here, and it shows the cash flow, and it's SEK 18 million better compared to last year. It's mainly better because of higher production of around 25% compared to last year, and also depreciations of SEK 10 million less compared to last year because we use the book value as the base now, not the investment cost as the year before.
During this half-year, we have sold five apartments on Vasagatan 33, our co-op project there, and also the large property in Helsingborg, Mässhaken 2. All this is recognized under the line development property sales, and it amounted to SEK 85 million for this half-year. Now turn to page 11. We recognize changes in value of almost SEK 550 million, where more than half of it is from our new construction. Now, I will talk about the value changes in our investment properties. The value changes of our existing properties is the result of higher NOI. We have not changed the yield requirements on no property. The 10-year swap rate has fallen from 1.12% down to 0.53%, which is the reason to our unrealized value changes of the financial instruments of SEK 425 million. It is very low now.
The taxes were affected positively with a one-off effect last year of SEK 272 million because of the lower corporate tax rate if you compare this half-year with last year. That is the big difference. Now turn to page 12. The assets are SEK 5.5 billion higher compared to last year, and it is mainly our investments in properties which contribute to that and the increased value in our existing properties. Since January, we also recognize lease liability of SEK 421 million in the balance sheet. Now turn to page 13.
We have almost 3,100 apartments now under construction, and they would create value in our management in the future, but also during the building process. This year, we will start to occupy 525 apartments gradually, and you can see them here in this slide. Now turn to page 14. We have invested SEK 1.6 billion in total in our properties this half-year. It is both in new construction and also refurbishment in older properties. Here in this amount, there is no investment cost of land. It is just construction cost. Now turn to page 15. I will talk a little bit about our start during this second quarter. Please turn to page 16.
As last quarter, when we started our big project here in Kallebäcks Terrasser, this is the second phase in this big urban development project here. Now we have 435 apartments under construction here of a total 1,800 apartments in this area. We will also build, as you can see on page 17, so please turn to page 17. We will also construct a commercial space here along the E6 road. It is also in this area, 20,000 sq m commercial spaces. Now turn to page 18. We keep our strong financial position, and the surplus ratio is higher compared to last year, and the ICR is a lot higher compared last year, and the reason is the realization of derivatives last year with the SEK 776 million, which affected the ICR negatively last year. Now it is 7.4x . Now turn to page 19.
We work with business plans, as you may know. Our goal for 2023 is to create a net asset value growth of SEK 40 per share. We have created SEK 1.40 to the net asset value. In total, it is SEK 4.50. The goal is to reach SEK 40 in value growth. Now turn to page 20. This was the end of this presentation. If you have any questions, you can click on the letter and send us an email and I will answer it.
Thank you for listening.